Quick question for the people living in the US (Target customers of the Powerwall). What is your yearly power usage?
On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. This is why this totally informal and unscientific survey :)
Helsinki, Finland here. Roughly 2100kWh/year. 2 people, a flat with 2 rooms + kitchen. We have district heating. Several laptops in the house, frequent home cooking, most lights are LED based, no sauna inside the apartment. We don't pay any attention to manually saving electricity, i.e. turning off lights etc. Our electric company provides a comparison report on their web site, according to it we are well below the average for similar household.
I have a solar installation which makes it slightly harder to work out what I've actually used - I know what I've generated, and what I've paid for, but since the metering isn't net that doesn't quite let me work out actual usage.
What I think you can see if you poke about the graph is that solar is very variable in practice. There are days in summer when it doesn't break 500W at all, and in winter there's basically nothing for a couple of months.
I'm happy with the installation and its return in feed-in-tariffs, but I wouldn't consider going off-grid unless I had to and had space to put up a wind turbine.
Edit: my heating and cooking energy comes from mains natural gas, as well; currently this is far cheaper than electricity. Might be useful to include that in comparisons.
I don't know if this is available in the UK but in the US we can get devices like the one I got that allows us to monitor our usage and calculate usage vs generation.
https://rainforestautomation.com/rfa-z109-eagle/
http://pvoutput.org/list.jsp?userid=41746
This web site collates all the data from your solar system (again, if it supports that like my enphase system) and the power company. $10 per year donation.
This is all a bit involved to setup but the end product, that iOS app, is just brilliant. It just takes the data from pvoutput and massages it into an addicitive portable display. 1.5 years later and if the monitoring system is down for more than 12 hours my wife yells at me.
I am ignoring the powerwall because we have a sweetheart deal with net energy metering in southern california and the power delivery has been rock solid. So it would just be a minor insurance policy in case of a catastrophic event.
But many parts of Europe need heating instead of AC. I think it has more to do with house sizes. More Europeans live in cities compared to US and thus have on average smaller apartments/houses. Also there might be cultural values in the play, at least central and nordic countries are traditionally quite efficiency oriented.
Electric heating is rarely used; there are many other heat sources available. There are no other energy sources available for cooling (passive cooling design aside), so comparing a heating-dominated climate to a cooling-dominated one will inevitably show more electric consumption in the hot zone. Has nothing to do with efficiency.
This left me curious and just checked that in EU, 50% of emissions are due heating and cooling [1] whereas in the US 20% of residential electricity [2] is used for air conditioning. I'd like to have better stats, but assuming numbers are correct this indicates that the difference of CO2 emissions between US and EU per capita are due other reasons than a/c use in US.
It's much, much better to burn fossil fuels for heat than to burn fossil fuels to spin turbines, transmit the electricity long distances, and then run it "back" through heating elements. Stages one and two are pretty lossy.
Particularly when electricity is from coal and natural gas power plants, using it for heating is a staggeringly bad idea.
I think you're right about house sizes, but there are a lot of the US that needs both summer AC and winter heating - like the midwest, the north east, and probably the west coast east of the mountains (inland Washington, Oregon).
Insulation is key. From what houses I've seen in the US vs Europe, the former are mostly wood-based (or similar material) and thin-walled, whereas Europe's houses are often stone- or concrete-based, thicker walls and/or (at least for newer/refurbished houses) very good insulation.
Combine that with some (more or less) clever thermal management and you need way less for both cooling and warming the house. There's also multiple government programs/incentives to improve housing energy consumption efficiency.
Do people need air-conditioning or is it just a luxury?
I guess now the globe is heating up there is more need for one, but I've always thought of it as borrowing from the future a little, a viscous cycle. More AC, More emissions, needs more AC.
I'm in Indonesia right now and sure the houses are built for the tropics but with locals, AC is rare and people manage to get plenty of good sleep and have loads of energy.
It's rarely productive to talk about "need". Do you really need indoor plumbing? Do you need a private bedroom? A broad variety of foods? After all, plenty of people in the less developed parts (and in the near past in the more developed parts) of the world get by without those just fine.
The history of civilization is largely the history of the taming of nature to better suit the needs (and wants!) of humans.
* 150-year-old rowhome in central Pennsylvania, USA.
* 2 adults, 2 small children, dog/cat.
* Window unit air conditioners (2 running most of the time in summer, with a 3rd in the attic office running a lot less since I don't use it much). Hoping to install mini-split system eventually, but it's low priority
My usage over the past year is just a hair under 14,000 kWh. Around 1500/mo when the A/C or baseboard heaters are on. Lowest months were April/May when both of those were off and I dipped down to 500 kWh.
If my math is right, most of the rest may be due to ceiling fans -- we have 5-6 that are left on pretty much year-round. Assuming they're each 75 watts, that's around 50 kWh/mo per fan. It never occurred to me to wonder how much power they might use.
So, if I leave A/C and baseboard heating off, and only run fans in currently-occupied rooms (bedrooms at night, living/dining/kitchen during the day), my usage would be about 4000 kWh/year.
How do you use so much less? Tiny efficient fridge? That's the only big item left in my house.
That's quite similar to me with a 4BR in Massachusetts.
I'm in the 550-600 kWH range for most of the year. Goes up a little bit in the summer if I'm running my 1-2 window unit ACs on occasion. In the summer, I do run several fans more or less continuously.
I do have an electric oven, dishwasher, washer, dryer, and several refrigerators. I also still have a fair number of halogen or other incandescent lights although I'm slowly swapping in LEDs. On the other hand, it's mostly just me and I do a fair bit of traveling so appliances and lighting probably don't add as much as they could.
I have a little bit of baseboard heat but I rarely use either that or my space heaters. (Forced hot water heat and water heater.)
My electric company says my use is about average in the area for the size of my house (albeit their figure is a few hundred square feet too low).
I've got an 80-year-old row house in Queens, NY. Family of 4, no pets.
Our electricity usage is well below yours. We don't make a huge effort to
conserve, and I don't believe our house is particularly well insulated. We have
no special energy tech, unless you count the LED lights. We have a lot of
electronic gizmos sipping away at any given time.
Winter: we don't have the baseboard heaters, but I work from home most days
and have an infrared heater pointed at my desk for a good 8 hrs or so each day.
Summer: my wife hates A/C when she sleeps, so we only have one air-conditioned
room at night (me and 1 kid in the room w/ A/C, wife and other kid in the
other). No pets, so we leave the A/C off when we're out, it comes back on (by
timer) about an hour before we get home. So big difference in summer.
Still, that doesn't sem to account for all of the difference. I just checked my
con-ed history online. Some typical usage numbers:
We spend anywhere from $80-$350 a month for electricity. Maybe there's a big difference between an 80-year-old row and a 150-year-old row?
We have
- 3 window A/C units.
- 3 routers, running 24/7
- 2 servers (mostly used as NAS), running 24/7
- FireTV, a few sonos devices, drawing a bit 24/7
- Many lights, mostly LED. We're pretty good about turning them off.
- ~10-15 phones/kindles/laptops/tablets/gizmos constantly being topped off
- Gas for stove, water, and household heating
EDIT: After reading more discussion below, I thought maybe I'd made a mistake, since there is a difference between our usage and most of the other US folks. I double checked, and the numbers are right. Our total usage for the last 12 months is 4340 kWh. We were gone for a few weeks in the summer, else it would have been a bit higher.
The reason their calculations are so high is because in the US, typical houses are made as cheaply as possible, pretty much with paper, plastic and vastly insufficient insulation.
That may have changed in the recent years, but holds true for most residential properties built before 1980.
Furthermore, unless you're in an area of the country that requires the use of a lot of AC--or you have electric baseboard heat--insulation doesn't even play that much into electricity usage.
I can see why one would bristle at the term 'cheap', but where energy efficiency is concerned there is a big difference between the EU and US. Energy costs are higher, regulations tend to be stricter, and usage lower in the EU.
On insulation, I'm assuming you mean in areas where AC isn't heavily used insulation doesn't help electricity bills if heat is provided by gas/oil?
>On insulation, I'm assuming you mean in areas where AC isn't heavily used insulation doesn't help electricity bills if heat is provided by gas/oil?
Correct. Heavy use of electric heat is fairly uncommon as it's relatively expensive. (In the Northeast, it would be considered a serious negative if a house had only electric heat.) Of course, insulation helps with overall energy usage if there's either a lot of heating, a lot of cooling, or both--however it's provided. I'm also sure the US tends to have larger houses, more large electric appliances, and other home features that increase electricity use.
Seems like Western Europe is getting up to speed with standardized insulation. People are monitoring heat leaks in buildings etc.
Two things: 1) I wonder how much energy could be "saved" with proper insulation. Per Country, per planet. 2) Insulation seems like a human sense, by that I mean, whenever I've lived in an old, stone wall house, I enjoyed the delay in temperature. It's still refreshing when the sun hits hard, and still mildly warm when cold settles.
More efficient lifestyle and better quality of life ? I'd sign.
Partly inspired by this thread, I read a couple of EU reports and realised that 50% of energy consumption in EU goes to heating and cooling. That is huge. Of course it includes industrial heating, but that is 18% in total (~third of 50%).
Clearly, there is lot to win here,with existing insulation techniques. we could do a lot in a short-term with existing technologies, it's mostly policy and financing issue.
It's really going to depend on the location in the US.
When I was living in the southwest, my energy bill per month was ~$500 for a 4 bedroom house. A/C eats a lot of power. After moving to the northwest, my bill is around $80/mo.
I'm unsure about the US but I know that where I live a solid third or so of my power bills are a fixed rate that you pay to access the grid (so pretty much line rental). It doesn't feel to me like that's a particularly unique situation.
So it's worth keeping in mind that the actual power usage figure may be a fair amount lower, and that your SW calcs are a bit of a worst case estimate.
That's not the case on my bill in the Northeast. There's a $4/month customer charge but everything else is kWh based (whether from the supplier or the distributor).
> The big difference is because of air conditioning and baseboard heating (...)
Which makes you wonder why there is not as much high-profile attention on A/C (and to a lesser extent electrical heating) as being a problem worthy of rethinking by Silicon Valley (perhaps even ahead of solar, in North America).
It might be (it is) anecdotal, but as someone from Europe it struck me odd how much Americans love their A/C. Too much, in fact. Almost everywhere I went it was too cold. Somewhat like in SE Asia. That might be the answer to high energy use.
Another anecdote: I live in Belize and my girlfriend runs a hostel, and we can always tell which rooms have guests from the southern US because the AC will be set to 18C (~64F). For some reason northerners don't tend to do this, I assume because they don't use AC as often at home. The Texans I know are the worst. They make their apartments so cold I need a blanket if I'm going to stay for a movie, and they sleep under massive down comforters. In the tropics! It's so maddeningly wasteful. I rarely use my AC and sleep under a single top sheet with no discomfort.
I live where it tends to get hot and humid (not tropics humid though), but turn on A/C only if it's really unbearable at night. Even then, at most 5C difference. Usually, single top sheet, as you've said, a cool drink and maybe a fan is enough. I understand that humidity is tough though, but one can get dehumidifying alone from A/C or a standalone dehumidifier.
For Americans, mostly read Texans or maybe Southerners more broadly. A lot of us joke that the hotter the climate in a US state, the colder they tend to crank the AC.
That can't be good for health! SE Asia like to do that too. I joked that tropics there were a sham since I had to wear a jacket all the time because of the polar-like A/C.
It's worth noting that temperature control is only half the equation. In places like Houston, A/C plays a big part in controlling indoor humidity as well(for both comfort purposes and to prevent mildew from growing all over everything).
There's other (read: more efficient) ways to control humidity than using an A/C. Including making buildings more "airtight" so the dampness doesn't leak into the house (as long as you don't open doors/windows too much, of couse).
I have the same experience in both US (mostly Raleigh, NC) and China; but China has got better over the last twenty years, possibly because air conditioning is no longer an unusual thing in the big cities so it being cold indoors is not such a status symbol, perhaps.
There is quite a bit of work being done on solar powered airconditioning. I experimented myself with this about 10 years ago using two back-to-back Stirling engines with the first powered by the sun and the second being run in reverse to cool a working fluid.
It's an interesting field, you'll learn more about Carnot cycles and thermodynamics than you ever wanted to :)
A climatization using DC current from capacitors charged with solar panels might be more interesting in mild hot regions.
If I understood well AC is optimized for carrying current on long distance with minimal loss. But most electric devices use DC. They need an AC to DC convertor with some energy loss.
Solar panels produce DC and is usualy converted to AC with some loss. Then, in most electronic devices, this AC is converted back into DC in the device power transformator.
What waste of energy. Shouldn't we do something about this ?
> What waste of energy. Shouldn't we do something about this ?
Most devices which operate on DC (e.g. computers, TV) have a switching power supply, which is around 90% efficient. So for a computer drawing 100W, only about 10W is lost in the conversion of AC to DC.
Larger appliances such as microwaves, ovens, and air conditioners will use AC directly without conversion to DC (except maybe to power the control electronics).
> But most electric devices use DC.
Yes, but no national grids are DC. There is a lot of interest in using high voltage DC (HVDC) for long distance transmission (and wind farms), since you don't have to expend energy to generate and maintain the sine wave (and your collector field electronics are simpler), but the customer connection is always AC.
With the insane amount of money invested in delivery to homes as 110/220VAC, no one is going to start selling DC devices. Even in regions where this is no electricity and people use off-grid systems, the economies of scale mean that DC appliances such as refrigerators are often 200-400% more expensive than their AC counterparts.
A lot of research has been put into DC distribution, but the main issues are:
- Devices still require a DC/DC converter to step up or down the distribution voltage to their operating voltage. This converter is again not 100% efficient
- High voltage DC is deadly (your muscles will contract instead of releasing, so if you touch a cable you're dead)
- Low voltage DC requires thicker wires, meaning higher cost for distribution
Another factor is that high voltage DC step-down is significantly harder than AC step-down, especially once you get into the 100's of KV. With AC that's relatively easy, transformers are passive components, very well understood and can be made for extremely large power levels without getting into exotic engineering.
Don't forget gas for heating in Europe. One cubic meter of low caloric gas approximates 10KWh. My household (Netherlands) uses 4k KWh but also 3k m3 north sea gas. So about 34 KWh equivalent total. Suddenly a not so different ballpark. (And I have an eye opening moment. Never knew gas was so full of energy.)
I used a little over 12000k Wh/h over the last 12 months in a 4bed with 2 people in Texas. I also have 2 cats and 2 dogs, so I don't turn the AC down too much during the day.
date-elec-solar
10/15-567-503
11/15-329-312
12/15-290-373
1/16-270-493
2/16-218-535
3/16-269-543
4/16-352-509
5/16-510-383
6/16-994-492
7/16-1292-514
8/16-976-401
9/16-832-???
I changed the password on my router in September and didn't update my solar controller, so I don't have data for my September solar production, but it was probably around 500 (I produced 579 last September!).
I live in California, 4br house with four adults. We use about 200kWh/month in the summer time which is basically just lights, electronics, and fridge (water and stove are gas), and 1000kWh/month peak in the winter time because we heat our rooms with electric space heaters.
We don't own the house so there's not much we can do about it. The windows aren't really insulating at all, and there's one old gas heater that doesn't work, although even when it did it all the heat just went straight up the stairs.
In the summer the upstairs gets extremely hot. But our rent is very cheap compared to other places in the bay area, so we are afraid to bother the landlord about these things. #freemarket
We use heat pumps as well in Northern Europe, but to transfer heat from outside to inside. You can get even five times more heat for the invested electricity compared to direct (resistive) electric heating. The best winter optimized air-to-air pumps work down to -20 °C (-4 °F) with efficiency ratio over 1. For example, I heat my entire house with a single heat pump through the year. Our average electricity bill is ~100 €/month. There are less than ten days in middle of winter when I turn on extra resistive heaters.
Unfortunately, although in Southern Scandinavia we receive about as much sunlight energy than Northern Germany per year, the peak is in summer when the need of energy is lowest and during three winter months almost no usable energy can be harvested from sunlight, meaning that solar-only powered house would need gigantic battery bank (~100 Tesla Powerwalls) to survive over three darkest months.
I heard great things about heat pumps efficiency-wise, but that their downside were noise. However, that information is dated because I haven't looked into it in a long time.
Has that improved? I'd expect the market in Scandinavia to be much more developed than in my country.
It's unfair to compare European and American heat pumps. The market is much larger more mature here in Europe and the differences in how you think about heating are large. I've heard that american heat pumps are quite noisy, mainly because you place them away from the living area (there's no reason to lower the noise). In new-built houses here in Europe they are most often placed directly within the living area so the heat pumps must be very quiet.
Disclaimer: I work for one of the heat pump manufacturers in Europe (albeit with connectivity solutions and not actual heat pump technology)
Depends how much you pay. The last time I looked a simple air to air pump the cheapest was 31dB and the most expensive was 21dB. So very quiet indeed.
About one in five houses have heat pumps where I live (about 40km south of Oslo) and I can hear them humming as I walk past but of course they are not the latest models. Still they are orders of magnitude quieter than the units outside the flat I rented in Cary, NC ten years ago.
Air-to-air pumps will probably always make some noise because air has relatively small thermal capacity, requiring relatively big air flow in order to transfer any meaningful amount of energy.
There also exists heat pumps which transfer heat to water-based central heating system (radiators / floor heating), eliminating the noise issue. The heat source can be either outside air or liquid circulating in soil/well (possibly supported by solar). All these combinations are relatively common in Scandinavia, air-to-air pump being most popular because of quick ROI (small initial investment) and easy retro-fitting, althought practically all new houses are built with water-based central heating (the heat source being either of electricity/solar/wood/air pump or any combination).
Effectively, we do not have AC and our heating system is not heat pump based but using the local district heating. This means that this power usage is only for: cooking, lights and computer/tv/etc. appliances.
My 2300 ft^2 (210 m^2) house in NC uses 11000kWh per year. I needed less than half my roof (the southern half) to be covered in solar panels to generate almost all my electricity (I do have gas air and water heating, however).
I'd like to build my next house to PassivHous or similar standards. I think I can get the energy usage to 5000 kWH anually. With the whole roof sloping southward, I think I'd be able to generate more than what I need for the house, even accounting for electric transportation.
Ireland, 4 bed detached, solar water heater which works well for about 4 months of year, oil heating + wood/turf stove for rest of time. No need for air conditioning here but heat recovery thingie is on all time.
5000kWh last year, tho I have computer(s) on 24x7 due to home office, Comes to about 120€/month
Half of all the bills are just standing charges, and renewable subsidies charges and taxes, and taxes on taxes. Hence adding LED lights, low power appliances etc did little to budge the bills
We worked out recently that we spent under £20 pcm on gas and electric over the last year. 2 people, washing machine, fridge, 2 x laptop, LED lights, 1 LED TV, and gas heating. Admittedly we only put on heating in the evening for an hour or so. Southern England (UK). Attribute to it not being cold for the last two winters here. Duvets and hot water bottles are used regularly. Yet to turn on heating this year. Not looking forward to the cold. Water bill however is shocking.
That's a very interesting number. Here a comparison, from Germany too: I used to live with 3 flatmates for several years in a 4BR apartment (165m²), our yearly usage averaged 5500-7000 kWh. That included heating water (electric boiler), but no room heating or air conditioning.
I've recently moved out into a 1BR, 63m² apartment, and am targeting 1500-2000kWh - don't have any usage numbers yet since it hasn't been long enough, but those seem realistic to me.
Amsterdam, Netherlands. Around 1200 kWh/year. 1 person, flat with 1 room + kitchen. I am not home that often due to my job/hobbies, but I do have a gaming PC and a laptop. I did buy a power efficient refrigerator and washing machine when I moved in (Not terribly special or something, just bought the ones with a certain label). I also don't have a dryer and I cook using gas.
I'm guessing that would be below peak day usage for me--i.e. two window AC units running (which isn't common)--but 14600kWh/year seems pretty close as an average based on my $100 or so monthly electrical bill. That's for a 4BR house, albeit a smallish one, that uses oil heat almost exclusively in the winter and runs fans, and only sometimes AC, in the summer.
My electric company sends out a comparison statement periodically and says I'm about average for similar-sized neighbors. (Albeit, it thinks my house is a bit smaller than it is.) So I'd say Tesla's calculator is about right for the US although it's going to vary a lot based on AC and electric heat.
1BR+office (home office with 2 always on computers), air circulation with filtering, around 80 square meters, 2 people, also Germany, 3600kWh/Year (~90€/month)
That could probably triple if we had AC. Far worse if we had electrical heating.
I'm in the US (suburbs near NYC) and over the past 12 months we've used 15714 kWh. 5 bedroom house built in the 1950s. With all my electronic toys, our love of air conditioning in the unbearable NY summers, and the tendency for nobody to pay any attention to turning things off, I'm almost surprised it's not higher. Also, we have a Nissan Leaf (electric car) which is responsible for 2500-3000 of that usage. Total electric bills for the past year comes to $2885. I don't think we get enough light here for solar to be worth it, but occasionally I think about it.
It probably depends on number of electric appliances.
If you live where you have electric heating/cooling, electric water boiler, electric stove/oven, you'll burn a lot of electricity. I burn 2500-3000kW/year in 1B apartment, but except heating/cooling - everything is electricity. If I had a gas stove and hot water I'd probably use less than 1/3 of that.
Also I'd guess that in US people do not built as well insulated buildings as in Europe, thus more power for heating/cooling
Our family of 4 in a 4BR house lives in the humid SE USA. We use about 5000 kWh/year. Our efficiency report says we use roughly half as much as comparable households.
Another data point. Past 12 months we're at 22,000 kwh. Average of 60kwh a day. Older 4 br house with people almost always in it. USA, TN.
I think the main difference for us is that my wife and some of the kids are at home almost all the time and we kept the house warmer for the baby this winter.
Over the past 12 months, 12000 kWh, in the Pacific Northwest [1]. I expect that to be lower this year, because I just had my house insulation improved. My house was originally a two bedroom house of approximately 1000 sq ft (92 m^2) built in 1964, and an additional bedroom was added in 1984, bringing it up to approximately 1400 sq ft (130 m^2). There was no insulation under the floor in the original house, and just a small layer of some kind of shredded paper-like material in the attic. The added room had decent insulation under the floor, and some real insulation in the attic, although not up to current recommendations for attics in this area. I now have a properly insulated floor, and the whole attic has been brought up to R49.
Here's a month-by-month breakdown, giving kWh for the month and average temperature.
2015-11: 730 kWh, 54 F (12 C)
2015-12: 1780 kWh, 42 F ( 6 C)
2016-01: 2100 kWh, 40 F ( 4 C)
2016-02: 1600 kWh, 43 F ( 6 C)
2016-03: 1420 kWh, 46 F ( 8 C)
2016-04: 1130 kWh, 48 F ( 9 C)
2016-05: 580 kWh, 57 F (14 C)
2016-06: 460 kWh, 59 F (15 C)
2016-07: 490 kWh, 62 F (17 C)
2016-08: 460 kWh, 66 F (19 C)
2016-09: 530 kWh, 67 F (19 C)
2016-10: 560 kWh, 59 F (15 C)
(Note: dates are the dates on the bills, which come about a week into the month, so the actual period covered is mostly in the prior month)
Rates here are $0.09/kWh for the first 600 kWh per month, and $0.11/kWh for whatever is over 600 kWh.
I don't see how you can use so little power. 2550 kWh/year is under 7 kWh/day.
During the summer months I turn my heat pump off, doing climate control by opening windows and using a couple of box fans to ensure air flow through the house. I typically have two fans running at opposite sides of the house. Figure 50 watts each, running whenever I'm home (weekends, plus one day a week working at home, plus 2/3 of the day on days I work at the office), and that comes to about 2 kWh/day average.
I usually have my entertainment system on when I'm home. If I'm using the TV, it's a total of about 100 watts. If the TV is off because I'm just listening to the streaming radio services my cable provider provides, it's about 60 watts. Call it 75 watts on average, and rounding to the nearest kWh, that's another 2 kWh/day.
My desktop computer uses 150 watts when used casually, such as reading and posting on HN, or browsing the web. Figure 4 hours a day on the computer on work days, and double that on my work at home day and weekends), and that's another kWh.
I'm up to 5 kWh/day now, just for fans, TV/stereo, and one desktop. Then there is my refrigerator, the pump for my well, my water heater, a washer and dryer, cooking appliances (stove, oven, microwave, electric griddle), and lights. Some of those use quite a bit of power. For instance, cooking baked french fries in the over (preheat to 450 F (230 C), then bake for 35 minutes) uses 3 to 4 kWh. I only do that maybe once a week, though, so it maybe contributes 0.5 kWh/day. Lights (all LED) are probably about 0.25 kWh/day (mainly two 14 watt (100 watt equivalent) Cree bulbs running 8 hours a day). All in all, these other things are going to probably average 2 to 3 kWh/day combined...and that puts me at or above your usage.
So, best case I should be able to maybe get down to your usage, during times of year when I can turn off the HVAC system and rely entirely on a couple of fans for climate control. And the best I've actually achieved is twice that...which means I've got something drawing more power than I accounted for above. My first guess is the refrigerator, as it is quite old. Time to stick the Kill A Watt meter on it and see what it is going on. The only other things I can think of that I left off are battery chargers for phone, tablet, handheld ham radio, and rechargeable batteries.
During months when I have to use the heat pump, I don't see any way I could get down to anywhere near your usage. How do you keep your house warm in winter?
I have noticed that if it is sunny out, then if I open blinds and drapes to let the sunlight in, I can reasonably heat the house that way even if the outside air temperature is low. I did that today, and got the house up to 68 F (20 C), and the insulation was good enough to keep it warm enough to keep the heat pump off for most of the night. It's now 4 AM and 43 F (6 C) outside, but the heat pump has not come on yet. Unfortunately, it is usually overcast during most of the winter around here so most days that won't work.
14,130 kWh for a 4000 sq ft 4 bed in Boston over the last 12 months for a 150 year old house. It looks like AC is a large portion of that. Thankfully, we use gas for heat and cooking.
For those who are looking for something similar but (being the kind of people who read HN) would like something more configurable and hackable, you might check out the products of Victron Energy[0]. They've also have an optional remote management portal[1] which allows you to set up and monitor everything remotely for years now, and most the software running locally on the devices is open source and fully modifiable (such setups are even supported!).
Full disclosure: I'm one of the developers of the mentioned Remote Management portal.
Solar panel roofing tiles have been around for a long time. I wonder what this will do different? Pricing? Or perhaps they are relying on brand strength alone.
Edit: I understand the urge to downvote because I'm not singing praise, but I promise I'm not trying to be overly pessimistic or critical of what Tesla is doing. Fact of the matter is, solar tiles have been done before, and failed miserably.
Marketing and business model, primarily. Previous solar tiles were more expensive than conventional solar and so are these. The difference here is that Tesla and SolarCity are marketing it as no more expensive upfront than a conventional roof replacement by keeping ownership of the roof and having buyers sign a contract committing them to buying power from it at ever-increasing prices.
There also seems to be some efficiency and aesthetic improvements over previous tiles, but those alone wouldn't be enough to make it viable.
And from that, hopefully, scale. Solar tiles have always seemed to be a very poor relation of solar panels. The approximately 1x1.5m panel is a sort of informal global standard, and that's meant that solar tiles have been much more fragmented, much lower scale, and much more expensive.
On the other hand in theory these solar integrated building materials should greatly reduce the associated costs of installing panels - labour is usually something like half the cost of installing rooftop solar, but if you can install a solar roof without much more effort than a normal roof, those extra labour costs are massively reduced.
If you can leverage this labour cost advantage to ramp up scale of the tiles, and get them close to the per watt cost of traditional panels, this is how you can really make rooftop solar competitive. These labour costs are why rooftop solar is so much more expensive than utility solar. If you can greatly reduce them, total costs are much more tied to the cost of the tiles themselves, the inverter, and so on, where there is enormous leeway for ongoing reductions. Very exciting.
CIGS solar roofing tiles are (or were, not sure you can still get them) about 6% efficient. These are, according to what was in the TechCrunch article are over 20% efficient[1].
DOW's CIGS was pretty garbage compared to Certainteed's Apollo II system, which achieved 13.2% efficiency. [1]
There are also up-and-coming competitors such as SunTegra that hit 14.6% [2].
It seems like asthetic options and possibly efficiency improvements is what will set this apart from previous stumblings in this space. We'll see how this looks in the real world!
From my research they have never really been competitive to the point of getting any traction in their installation. They cost a lot more and provided a lot less power compared to standard panels. This seems promising especially if it is available so that it can be installed directly by home owners.
>but I promise I'm not trying to be overly pessimistic or critical of what Tesla is doing
The fact that you have to apologize for this on HN nowadays is hilarious. I agree. Both solar panels (and to a lesser extent solar roofing tiles) and the powerwall are have a lot of competition.
The idea looks good, though. I didn't catch pricing details in the presentation?
the cool thing is that they look good... they look like a normal roof at the angle you would see from the street in front of the house, but from above... from the angle of the sun they are transparent and you can see the solar cells.
I know some rich people that want solar but their neighborhood associations won't allow it, but I don't think they would not have an objection to these roofs. they look really nice....
I have been curious how they were going to compete with cheap chinese solar. this seems like a good strategy but one that may be easily copied.
Here in the UK we have "planning permission" which is basically the same thing. Round our way it's been used recently e.g. to stop people extending their houses over their off-street parking, which would necessitate them parking on the road - if everyone did it the street would be impassable, so it's fair to enforce that no-one does it.
Planning permission is granted or refused by the council though, based on the need and impact on surrounding areas. A HOA can stop you hanging your laundry out to dry on a line, force you to water your lawn x times a week, prevent you painting your house a particular colour, prevent you installing a fence, determine they type of vehicle you are allowed and whether it can be parked on your drive or if it must be in a garage. It is not really comparable to planning permission which is really only required for significant construction work or change of use ie. Shop to residential or vice versa.
Plus if the HOA members don't like you they can make your life difficult. Planning permission affects everyone equally. If a neighbour can extend a property then more than likely you can too, if you are refused it is likely all similar applications would be refused, you don't know the planning officer and they don't know you so no bias can be involved which make the whole process much fairer.
Just imagine if they wrote encyclopedias in your communication style.
Completely fictional example:
From Ye Great Book of All Scottish things, 856 year of the Lord, page 17:
- yepswatter : a very commonly used household object, just ask anybody around to show you one.
Unless the HOA rules have a stipulation about your roof shingles exactly matching the other roofs in the neighborhood, which is common. And boring a shit to look at. I hate HOAs so much.
If all they did was protect property values by keeping people from doing outrageous things, I might be okay with them, but they go way beyond that to the point where it diminishes the value of buying property (since you can't adapt it as you see fit). Municipal codes usually take care of the worst behavior, anyhow. Which is why if I ever buy land and/or a house, it will be in a more rural area. Then I can put a damn Tesla solar roof on it, build a shed with a different roof and paint it all purple with green stripes if I feel like it.
I lived in an HOA that took their rules way too far. Here is an example - paraphrased so your head doesn't explode: "You can't have any wireless devices without written permission, except a garage door opener and TV remote."
Right. Nice try. I joked with neighbors that we should all send one letter to them on the same day. A letter for each cell phone, wifi router, satellite dish, bluetooth speaker, etc.
This was in an area where many people were on wireless ISPs, there were a handful of ham radio antennas, etc. I asked someone on the HOA board why they didn't update or remove the garbage about wireless devices. The answer - it would cost to much to update the documents, so they don't try to enforce it. It is still crazy that they ever put it in there.
This HOA says no solar, but now that it is popular they also ignoring that.
This product strategy certainly seems easy to copy, I agree. That's good for humanity and bad for Elon financially (I think that's the point for him, I don't think he cares about money outside of more commas).
The product itself might be easy to copy, but im not so sure about the product *strategy". Solarcity does the full stack, from the solar panels to the installation to the management and storage. That's going to be hard for a Chinese factory to reproduce.
I don't think he cares about copies. Tesla is poised to be a battery company, so copies will probably buy his batteries. At least long enough for Tesla to move up the value chain.
Honestly though, he is freaking Elon Musk. If you don't think he can make the best version of this you are way underestimating what he has accomplished already.
Its all about fundamentals and he believe he can have a fundamental edge here.
The thing is cloud-connected, remote-controlled by Tesla. That presents a problem. Will the cloud service behind it last the life of the system? Most cloud services evaporate within five years.
"The thing is cloud-connected, remote-controlled by Tesla. "
If your use-case is backup power in case of utility failure, how does that work ? If utilities fail, the network connection to the battery may also fail, right ?
Right, so you won't be able to use an app to monitor your Powerwall while it's offline... the battery's still going to work. Backup and off-grid are advertised use cases. Tesla's cars have the "cloud-connected, remote-controlled" stuff too, but they don't stop in the middle of the road if you leave cell phone coverage.
The nominal product life is 5,000 charge/discharge cycles, or 13-14 years if solar powered. Maintenance monitoring, including battery deterioration, is remote, from Tesla's end. Will that service still be running in 2030?
There will have to be onsite maintenance for battery/invertor swaps long before any battery power product, let alone energy backup, reaches 5000 cycles of lifespan.
That's a Modernist house. Flat cantilevered or overhanging roofs, large expanses of glass, right angles, no attics, rare basements. Concrete and engineered wood as preferred building materials.
It's called Modernist, but the style is nearly 100 years old.
I have no particular desire to sign up just to watch the video, but I hope that the Powerwall 2 is compelling enough to beat out the LG Chem RESU.
For reference, the RESU is a wall-mounted Li-ion battery meant to be connected to a solar inverter. It seems to beat the Powerwall in basically every respect. It's a bit cheaper, it has a better warranty, and it has slightly lower advertised capacity but higher warranted capacity under basically all advertised conditions. But it's not cool and doesn't have a shiny video.
I suppose the main reason for the inverter is to go from DC -> AC.
The Powerwall 1 required an external inverter. What did that inverter do? Converted from the DC -> AC? The Powerwall 1 had DC input? I guess not, otherwise you wouldn't need the external inverter.
So this powerwall converts internally from DC - > AC -> DC (battery)?
> But it's not cool and doesn't have a shiny video.
If no one knows about it, doesn't really matter what the specs are. If you can't market a product it might as well not exist. I mean, congratulations on the engineering I guess.
I haven't looked into it yet, but I'm curious about using utilizing my Teslas in case of emergency for power. With 75kwh+ each (leased so no concern about cycles) I don't think I'd need a powerwall at home.
If you're concerned about emergencies: for $38 you get a self-contained LED camping lantern that lasts for 30 days on a single charge [1] at the lowest brightness, or 2 days (off at night) on full brightness. For a tiny fraction of the price of a Tesla-based emergency power solution, you could buy two of those for every room, plus an RV cooking gas burner and a big propane tank that covers heating, making food and hot water for washing. Hell, even a big diesel generator would be cheaper (not to mention it's readily available).
The main thing I'd really like to be able to backup is my (oil) furnace in the winter so that it could continue to operate in a power outage. Though,truth be told, I could get a bigger propane tank and either run some backup heat off that or a generator for a couple of my circuits.
Pretty much everything else can go out. Obviously food could spoil in an extended outage, but that's a fairly modest cost in the grand scheme of things.
How about installing a wood-burning fireplace? Super cozy also in daily life, probably adds to the resale value of your house, and you can keep firewood indefinitely as long as it's dry.
As for food: stock canned goods for a week. (There's a reason preppers have rooms full of the stuff.) You probably also want to stock bottled water for a week, just in case.
I have both a wood stove and a wood burning fireplace. The backup was part of my justification for getting the stove. I don't know if it would be sufficient if I lost power for an extended period of time in really cold weather to keep pipes from freezing but you can't guard against every eventuality. (I also worry about what can happen when I'm not around.)
As for the food, I'm close enough to civilization that I'm not too worried. Worst case I get snowed in for a couple of days. I won't starve.
Musk and JB got asked about this (I think at the 2016 AGM?). Their response was basically "yeah we get asked this a lot; No, because of the make up of the cells makes them inappropriate for the number of cycles."
Your better bet would be buying a $1000 2000W generator. 4 gallons of gas will give you 24 hours of peak output. About 2 gallons for less than peak output for 24 hours. They're pretty quiet, too, and smaller than a carry-on suit case.
Can you explain to me your economic thinking behind leasing two Teslas? Are you super rich or do you have some other thinking that went into that decision?
It's actually not a bad financial decision at all relative to other cars. Reasonably specced Model S montly lease costs after tax benefits come out to well under $1000/month. That's on par with a mid-high spec E-class or 5-series. Now factor in fuel savings and small business lease write off. Plus access to carpool lanes during peak hours and prime parkin spots.
For $3000 this would be easy to justify just to keep my computer and network operating. I work at home and our power goes out too frequently. Is usually just for 10-20 seconds and my UPS takes care of that. But sometimes it is out for several hours - I'll say several times per year. If I can't work, I can't bill.
Where are you seeing $3000? When I set it to 1 Powerwall it tells me:
One 14 kWh Powerwall battery $5,500
Installation and supporting hardware starts at $1,000
Total estimate $6,500
Requires $500 deposit for each Powerwall
Which still ties you to the 'grid' insofar as you need the natgas supply chain, even if you have a huge reservoir you'll eventually run out. Having said that, batteries and solar panels don't have an unlimited life span either.
I'm looking at buying a petrol powered generator for reasons other than home power generation, but it will be reassuring to know we have backup power at home, but I don't think I'm allowed to store any more than 25L in one container on my suburban property. I guess that would be 25L plus each of our two cars with full tanks.
It would be fairly trivial to convert a petrol powered generator to run on propane from the barbecue gas cylinder, I've had experience installing gas kits on carburettor engines in cars.
Good points. But for me, I live on 80 acres and it happens that the county natural gas pipeline runs under it. The easement (signed in the 60's) included the right to connect to the pipeline at will. When we built the house, we exercised that right.
So even though I am rural, I don't have to buy liquid propane to heat my house. I'm tapped into a 100,000 home supply line. Its been depressurized maybe twice for maintenance in 50 years.
Not a solution for everybody. But a pretty good one for me! And everybody else on the line.
Nice setup! How much did connecting to the pipeline cost? Making an individual connection to something so large sounds expensive, but obviously I have no actual clue.
Fortunately there was a hairpin(?) connection across the road, so I agreed to connect there. That means they didn't have to depressurize just for me. Cost nothing (easement terms). However they charged me for the pipe to run the 200' from there to the house! I could have negotiated that better.
"Which still ties you to the 'grid' insofar as you need the natgas supply chain, even if you have a huge reservoir you'll eventually run out. Having said that, batteries and solar panels don't have an unlimited life span either."
That is my thought - however, a previous comment in this thread indicates that the powerwall batteries are cloud connected and remote controlled by tesla ... so I am not sure how that pans out when you lose power and network connectivity at the same time (as happens where I live several times throughout the winter, sometimes for 24+ hours).
3 of my 4 adjacent neighbors have natural-gas generators. That gives you an indication of the power reliability here. Note that I don't blame the utility, and I'm not in some backwater ($1M+ homes around me). It's just that we really like our trees here, and sometimes a branch will break in a storm and take out the neighborhood.
My gripe with the generators is they are noisy. A Powerwall would be silent and would handle the typical outage situation. But so probably would a 3000VA UPS, which would only cost $1500.
Some places even managed to get entire sewer systems buried. Granted, that happened on a very different level of urgency (you really want shit to flow, and it only flows downward), but it gives the appropriate perspective on any excuses that are based on the natural scale of infrastructure.
The point is that for sewers there was no choice so we just swallowed the cost and got on with it. For power there was so we went for the cheaper less reliable option.
A UPS will require a battery replacement every 10 years or so, regardless of whether you ever have to go on battery power or not. The UPS should automatically sense the status of the battery and warn you when a replacement is needed.
Pick a model from one of the major manufacturers and look up the replacement battery costs to get an idea of what it will cost.
It's just a big battery that you can plug things into full time. When power goes out it instantly switches to battery power. It recharges when the power comes back.
I signed up for the original powerwall and as it turns out it's not Tesla - it's solarcity (I get it, they are the same now). Oh and by the way you have to have the solarcity solar panels installed and running for the powerwall to be installed, which has a cost of it's own.
My guess is that this isn't any different given this text:
Powerwall 2 is a battery for homes and small businesses that stores the sun’s energy and delivers clean, reliable electricity when the sun isn’t shining.
Powerwall makes a whole bunch more sense for solar storage.
If you're just using it for backup power off the grid, you have to convert AC -> DC -> AC again for use. I don't know the all up efficiency of that system, but it's far from great. Probably <70%
Interesting to see Tesla of all people estimating energy consumption on the basis solely of how many bedrooms your house has, and not adding on how many electric cars you need to charge...
How long are the batteries going to last? With phones, we expect the battery to deteriorate after a couple of years. This is an investment. Will it need to be replaced in a few years' time?
Right, but the question was about the batteries, which hang on the wall in the garage. Nobody has the expectation that such an appliance will last the lifetime of the house.
Solar panels also degrade, roughly 1% per year, and commonly have a 20-year warrantee. That is less than the 30 years a good roof will last, but in the same ballpark. I doubt anyone knows the long-term resilience of these solar-panel-tile-roofs, but it's unlikely that they will have the extreme longevity of the clay tile roofs they imitate. In the right climate, those clay roofs can last a hundred years!
The problem with phones is that they don't have good management - the battery doesn't have active cooling, or heating when needed. They're also charged to full capacity or depleted to empty a lot of the time.
Phone batteries get hot, but they have plenty of thermal connection with the environment. This is nowhere close to the magnitude of a heat problem you would have within a massive multicell pack, where the direct environment of one hot cell would be a few other hot cells. Active cooling is not something you add to a pack the size of a Tesla to make it survive a few more cycles, it needs it to survive the first cycle. But sure, once you have active cooling you might just as well try to make it powerful enough to create an environment that is even better than that of a single cell phone battery. Just don't hook overboard and have the cooling power demand cut noticeably into total cycle efficiency.
About cycle depth: Does Tesla come with an UI where you can do something along the lines of "I need to go 200 miles the day after tomorrow, do whatever you think is best for the battery in the time until then"? Or at least a setting "feel free to optimize from what you learnt about my driving patterns, except when I press the prepare-long-distance button"?
If not, most of that battery management technology will just be about not being worse than a single cell system. In that case, the difference in perceived durability mostly comes from a wildly different balance between depth of discharge and expected lifetime. Phone makers are quite happy with your batteries getting worse after two years, so they drive them over a wide voltage range, Tesla is in a market where they can't do that.
I suspect that drivers want their "fully charged" just as much as phone users, but I might underestimate Tesla/owners here. Maybe "battery wisdom" just needs some time to sink in. Sony is advertising a "top off the battery only just before the morning alarm goes off", this is the right direction (to bad that the new compact is a downgrade)
> Does Tesla come with an UI where you can do something along the lines of
No, not like that.
The charge UI interface has a 'daily' indicated range that you can set, and the top ~10% is marked 'Trip'.
Example from a screenshot of the mobile app shows what i mean[1]
The advice given to owners is to normally set the charge limit to somewhere in the daily range depending on their expected driving needs the following day.
As stated by others, it's most damaging to cells to be kept at the extremes of their charges. Controlling temperature is another big factor in it too, that's why Tesla has active temperature management in the cars and stationary storage products.
Here's real-world numbers from owners[2] and shows that the degradation even after a lot of miles and with older packs isn't terribly much.
Actually, that UI is pretty much exactly what I had in mind. All devices that control their own charging should have that "trip" switch. It's a shame that Android does not have an API to customize charge depth like that. I occasionally spend some idle thought on wondering how difficult it would be to overcome this limitation with a bluetooth-controlled charger. Well, I'm not an electrical engineer and "bringing the joys of self-asphyxiation to your phone" maybe would not be the most successful kickstarter ever either.
Most decent smartphones are already doing battery management and avoiding extreme draining or charging of the cells.
Think about it this way: If your phone has 8 hours of use, chances are the battery could really give you 9 or 10 hours if it was fully charged, but the manufacturer is software limiting it to prolong the life of the battery.
All things with a LiIon battery do battery management to avoid extreme draining or charging. I've never seen a phone that offered a choice of "more battery cycles vs slightly longer run-time".
For cars, it's not an unusual feature to be able to choose. The Leaf has that feature, and since it cycles its small batter frequently, it's an important consideration for owners. See:
No phone allows me to further reduce the voltage range in order to have a runtime/durability tradeoff other than the one the manufacturer selected to maximise replacement after 24 months.
"They're also charged to full capacity or depleted to empty a lot of the time."
Does it affect battery life if I keep my phone charged even if it's at 100% ? (My phone is charging during the night, so it will be at 100% for a long time and keep charging).
If it reaches 0%, how does that impact battery life compared to reaching 20% and charging up ?
I never looked up these things but it might influence how I charge all my devices.
Modern batteries deteriorate from heat and from the time they spend at the extremes of their charge cycle. As a general rule of thumb, you would get the lowest amount of wear by keeping the battery as close to 50% as possible all the time, only charging higher than that right before use and just enough to make it comfortably to the next charging opportunity. One of the worst things to do to a battery (not as bad as a deep discharge) is keeping it on full charge standby all the time. Think desktop replacement laptops.
For a while I only charged my phone in the morning when it was still at >50% in the evening, e.g. a 40%-70% charge. In the end, convenience prevailed.
Sounds like an opportunity to have scheduled charging. I'd like to plug my phone in at night and have the phone keep itself at some minimum until an hour before my morning alarm. Then start charging so it reaches 100% just about the time I wake up and unplug. Maximizing battery life might conflict with phone manufacturer's goal of getting you to buy a new phone every few years.
His argument about the solar roof starts by equating the situation to how Tesla started out - electric cars were slow and ugly and needed to be sexy and cool to be attractive, and the same is true for solar. Except I highly doubt this is true here - do people really mind the look of typical roof-mount solar? My impression is that the upfront cost is just too high and cost recoup is just too slow. The argument for the solar roof is then 'using a solar roof in the first place = way cheaper than installing on top of existing roofs (and also it looks as good and works better)'.
Maybe? I'd like to see the quantitative argument here. Having a house pre-built with a fancy solar roof AND a powerpack seems like it would still be pretty much for rich people. Still, maybe the aim is for a similar trajectory as Tesla - start with a product for rich people, make it attractive, lower cost so everyone can have it and WANTS to have it.
Unrelated: gosh, I like the content of the video presentation but it would be nice if Musk was a slightly better presenter.
The reason that solar roofs aren't common is that they're more expensive than rooftop solar. As I understand it, Tesla/SolarCity's argument isn't that they're cheaper than normal solar, it's that they're the same cost as normal re-roofing once you take into account the income from the solar. From the ArsTechnica article: 'In a private conversation with journalists after the announcement, Musk declined to state a price for the roof or a price-per-square foot. He did admit "it's not gonna make sense for somebody to replace a brand new roof with a solar roof." But if your roof needs replacing anyway, he said, the cost/benefit could make sense for many families.'
More specifically, since SolarCity's business model is that they own the solar panels and you're committed to buying electricity produced by them for their lifespan, his argument is that it costs no more than conventional re-roofing + conventional electricity. There is of course the slight downside of you no longer owning the roof over your head, and having to commit to electricity purchases for the next decade or so.
Every time Elon presents something we have this coversation. I for one love listening to him talk compared to say the presenters at Apple and Microsofts recent event. He's genuine, doesn't feel like a salesman, talks about the reasoning and science behind it all in a great way.
I dont agree. Not cringy and awkward, but human and real. Who cares if he stutters and doesn't bring a polished salespitch. And he's nerdy for sure, but why have it any other way. Also the few jokes thay occur are typically funny as they are genuine and not silly jokes practiced before hand like Apple seems to like.
That sounds like a false dichotomy. Recent Apple keynotes are more polished, but the content is often cringy too (that whole "courage" thing will go down as one of the most ridiculous things ever said in an Apple keynote). Not a good counter example.
But Louis CK sounds human and real and he can deliver something without stuttering, bad comic timing, and awkward pauses. You might say it's his job — but that's the point. It's a job. It takes skill.
Musk is just not a good public speaker, that's all. I don't think even he would disagree with that.
One problem with solar traditional roof mounts is that they are heavy, and many houses aren't rated to carry that much additional weight. In addition, they can affect the water flow on the roof, and then when you need to replace the shingles, you've got all of these panels in the way.
>do people really mind the look of typical roof-mount solar
It depends on the person and it depends on the house design. IMO, some roof-top solar installations look pretty ugly.
To your cost point, yeah, it's still hard to look at a lot of solar as something that works financially today for most people even with the price drops--if having an off-the-grid backup doesn't have a lot of value.
As various people here are quoting, $1K/year covers electricity use for a lot of people. Even if you double that to account for higher usage or price increases, it's hard to square that with a $20K or solar/battery installation even if you ignore maintenance and depreciation.
> do people really mind the look of typical roof-mount solar
Depends on the people you're asking.
Some Home-Owners-Associations in the US forbid the installation of rooftop solar on visual grounds. Though some states have signed laws stopping HOAs from doing this.
Note that what he said is that the solar roof plus the electricity that it generates is cheaper than a conventional roof. The up-front cost is higher for the solar roof.
So, yes, there are assumptions in there: how much power can be generated, how valuable will it be 10 years from now, etc.
This is big. My roof cost nearly double what my solar installs did, and getting the tax credit on the roof might have paid for the additional cost of the solar tiles over standing seam metal. (Not that I don't love the metal; it's awesome.)
Any idea why the solar cells aren't packed more densely? It looks like there's a lot of wasted space on due to a square cell centered on a rectangular tile.
That's not really how it looks in the pictures on their site. It looks more like they are butted together with no overlap. Also, I'd think you'd want just as much overlap on the long side for weatherproofing. This does raise an interesting question; how are they weatherproofing this installation?
From when I was reading more about solar cells I recall there being something about the distance from the conductor (the two stripes visible equidistant from the midline of the cell) being a problem especially with monocrystalline cells, which these appear to be. I think this was more a problem for cells that had the conductor fixed to the back of the cell.
Google image search for monocrystalline solar cell and you'll see they are all square. I had a brief go at searching for anything to back up my claim but lost interest.
I might simply be that the silicon ingot they are cut from is cast round, see this[1] picture and it's less wasteful to cut a square with chamfered corners than to cut a rectangle, which would necessitate an ingot with an elliptical cross section, which would probably be harder to cast due to uneven cooling, maybe.
I'm not sure you can even make a mono crystalline ingot eliptical. The process heavily relies on spinning the ingot while pulling it out of a silicon puddle which results in the round shape.
I've had a few moments recently where I've thought "how can it be I haven't thought to look this up on YouTube before now", and here we are.
I found this[1] video that explains how to grow a monocrystalline silicon ingot that weighs 440 pounds, and you're right it is spun as it's extracted from molten silicon.
Someone posted a link about Boston.gov being released as an open sourced project on GitHub. I'd like to take a moment to point out that this Tesla website is built on Drupal 7 too. The big thing that both websites get out of the box is i18n support for translation on top of all the tools required from content management. I wouldn't recommend it for websites and services that need many people to constantly update content but to build static pages that are cached is pretty awesome stuff.
Musk & co changing the world one step at a time. I used to be a Tesla sceptic. Not anymore, having owned one and witnessed the relentless improvement in battery tech.
That was my question as well, this from the Techcrunch article:
"The current versions of the tiles actually have a two percent loss on efficiency, so 98 percent of what you’d normally get from a traditional solar panel, according to Elon Musk. But the company is working with 3M on improved coatings that have the potential to possibly go above normal efficiency, since it could trap the light within, leading to it bouncing around and resulting in less energy loss overall before it’s fully diffused."
Which suggests that on a square footage basis it is similar. The difference being that on a manufactured panel the cells are all exactly next to each other with no seams, and with the Tesla roof they appear to have a moat around them that varies a bit with roof tile style.
That said, assuming you cover your entire roof which will include both "ideal" south facing (or north facing in the southern hemisphere) and "non-ideal" north facing parts of the roof you may get enough additional generation from the extra tiles to push it over a more 'traditional' solar install.To be honest I'm thinking about replacing my perfectly fine (if nearly 15 year old) solar panel set up with those roof tiles. That and a couple of power walls and I just might be able to go 'gas only' with PG&E.
replacing my perfectly fine (if nearly 15 year old) solar panel
I wish someone near me would do this, boy would I snap up those second hand panels.
When I was in my early twenties I put together a solar panel + charge regulator + inverter + laptop and run a web server serving a page detailing the setup it was running on.
The entertaining things I could get up to with 1kW or more of cheap second hand panels.
1) I'm wondering why the tiles weren't larger? Wouldn't this make laying them much cheaper in a world where labor is such a significant cost for building. Aside from the shingle look I'm surprised these dont come in 1mx1m type sizes plus some smaller sizes for edges. I cant imaging this want discussed so curious if I'm missing some obvious logic here.
2) If you didn't have a ceiling would these let light through and further reduce electricity usage?
3) The cells seems to be a small proportion of the tile. Is this something they expect to increase so they will increase power generation ability significantly over future releases?
This LNG ship got me wondering about a battery equivalent, charged up in a desert solar farm and shipped to a major city.
I get 16 Powerpacks per 40ft container 5100 containers per Panamax ship =81600 powerpacks per ship At 95kWh per pack = 7752MWh per ship ( based on powerpack v1)
So is that like two Hinckley C nuclear reactors worth of energy?
How long would that last before having to go back for recharging?
How long would it take to charge from a massive solar farm etc etc.
so many questions but basically, is it remotely viable?
One of their new projects is to ship heat, stored in phase-change material, from a generation plant to central Bristol on a barge full of SunAmp cells. So it's a similar concept, shipping heat batteries instead of Powerpacks.
Lithium Ion batteries lose charge over time, so during transport they would discharge.
Lithium Ion batteries can handle a relatively small number of recharge cycles (when compared with the number that a metal cylinder/sphere can handle when just filling it up with LNG)
I was pleasantly surprised to see prices quoted in £GBP - the Powerwall is available in the UK! But, we don't have enough sunlight here to run a typical house off-grid year-round, do we?
In the UK we get about a quarter of the incident energy from sunlight in Winter than we do in Summer. You could do it by overbuilding your solar array by 4 times over what's required in Summer. That might actually be reasonable if solar prices carry on going down. Or you could do it by having some sort of micro-CHP system which produced electricity and then uses the waste heat to heat the house.
But, yeah, I think this is the major outstanding issue with renewables at the moment. Solar with battery storage looks like it will get parity with the grid anywhere near the equator, where you don't need seasonal storage. The UK needs additional solutions. I think we should be putting more money into developing micro-CHP personally. British Gas were trying out a Sterling engine system a few years back, there are also some in development using Fuel Cells.
In the UK a lot of people are on tariffs which pay them above market rate for the electricity they generate regardless of whether they feed it into the grid or use it themselves. A battery like this will allow them to both sell and use 100% of what they generate.
I'm not following the calculations, maybe I'm sleepy. "can power a two-bedroom home for a full day". They say that is 20kWh (it doesn't change when you say sockets vs entire home...). They say the battery is 14kWh and only recommend one. Huh?
Good point. I'd imagine you could charge an electric car without an inverter. Perhaps it could be just for that purpose. Bury a line running to your garage.
Exactly the reason that many people are wise to hold off on installations. The long term cost savings are wasted if future products are exponentially better in the short term. Non-financial benefits aside, naturally.
I cannot imagine what preparation they could be making. Surely the default process is to charge the powerwall at all times if feasible. What extra operation could it do in the event of a bad weather forecast? Other than tell you about it.
To get better lifetime out of the cells, you don't fully charge them. I bet when bad weather is occurring soon, it charges to maximum storage capacity, not to max cycle level.
This lets you have best of both worlds, with a minor tradeoff in unpredictable outages you have slightly reduced runtimes.
Sometimes you discharge. You may decide to not discharge ahead of a storm. If it were just backup, it would be easy, but sometimes you want to consume your storage to save money, or sell back to grid, if you have time of use pricing, or get paid for grid service.
As much as I like the idea after reading about the Note 7 and then a battery fire at DARPA I'm not fond of a giant battery lithium-ion battery in my house.
The problems with those batteries are that cell phones pushed the limit such that they were dangerous due to thin walls between part of the battery(ies), and hoverboards didn't keep batteries from overcharging, which causes a chemical reaction forming spikes that penetrate the thin walls between the parts of the batteries that cause fires. The batteries tech itself is not a problem; it's the design around it.
And if you think this is bad, just wait until batteries get more powerful and there are problems. Be thankful that it only starts a small fire!
Lithium-Ion technology is pretty well-understood at this point.
Just remember that there are 10s or 100s of Billions of Li-Ion batteries around the world, and having a single one fail catastrophically is still enough to make headlines...
Tesla has lots of experience packing cells with their vehicles. I would trust them to get it right. Also they have much more space to work with versus a phone.
Correct me if I am wrong, it estimates 12,000$ for a single day of energy backup of your home? For 12,000$ I dont mind staying one day without electricity.
But my electric bill is like $30-40/month, Why would I want to shell out $12,000 for something that will become old tech in couple of years like the 1 powerwall.
30-40$ is probably a very small apartment. A house (2 levels) in Quebec during winter can go easily around 500$ because of the constant heating required.
Cooling a house during the summer in Texas can easily cost the same amount if not more, and you get a ton of sun during that time. The point is that for single family homes electricity does not usually cost $40/month.
But the price for the equal amount of power walls needed for a bigger house vs a small 1 bedroom raises too, according to the calculator on their site it will cost $30k+ to install it for 4 bedroom house.
It will take most people 20-30 years to recoup this in terms of an investment over wholesale energy costs at current rates. It is, for the present a gimmic.
Are the solar cells and powerwall shielded by any kind of solar storm? I couldnt find any detailed information confirming or denying it. I would not like for any of us to be in a situation where the 1st solar outtage is our most damaging, and thats what causes any producer of electronics to adopt labeling and marketing for it.
Solar storms don't reach the earth, one of the jobs of our atmosphere and magnetosphere is to protect us from it. So there's no point in making protections against it for solar panels on the planet.
Not to mention that coronal mass ejections (CME) happen so often that you'd expect to have already heard of such power outages if one were possible.
You can buy 12v 250ah deep cycle AGM batteries from China for around $5 per battery -- lets assume another $15 for world-wide shipping. These kind of batteries would have around 3kwh of storage per battery but since you shouldn't discharge them to more than 50% lets also say that you need to double the number of batteries to achieve 14kwh of usable power for 28kwh of total capacity. At that capacity level, you would need only 9 batteries for a sub total of just $180 USD (including shipping.)
Lets proceed with these calculations and say that you also want a good quality "grid-tie" "pure sine wave" inverter (to feed your stored energy back to your home grid) which will set you back any where from $100 - $1000. Your total cost for energy storage is still only going to be around $1180 (worse case.) Now consider that the life time for the Tesla batteries and standard AGM batteries seem to be very similar and I honestly have no idea what the customer is actually paying for.
Is the compact size and sleek appearance really worth the extra cost to the customer? Maybe it is. Maybe people don’t want to have a nerdy battery bank in their homes but to me the benefits all seem a little petty. (Granted, I definitely do see the benefit for tech like this in electric cars though, don’t get me wrong.)
And once your self made cheap chinese battery pack ends up catching fire and taking your whole house with them you understand why you want to pay for some actual company to do this and have some quality control/insurance.
Are you sure about those shipping costs to a residential address...? Professional installation? Process and guarantees from a reputable American OEM? Breakdowns and warranties?
I think you're missing a lot of costs beyond the raw materials...
Regarding professional installation, those costs are not factored into the base price. It's an additional cost to both parent's DIY method and the Powerwall.
As for reputable warranties against breakdowns, please check out the fine print of the Powerwall warranty terms and conditions. It's a '10 year warranty' with some very special legalese baked inside that may make you reconsider the cost premium commanded by guarantees provided by a company very adept at lawyering up and navigating regulation.
The warranty (at least in North America) has provisions for voiding warranty claims in off-grid scenarios: during the entire period from installation to claim you must have constant access to the Internet for remote updates. If Tesla detects you go offline, they reserve the right to deny your claim.
In addition, if you use the Powerwall for additional applications besides self-consumption of solar power, you're capped at 18 MWh aggregate throughput before the claim is denied. Consider a 6 KWh solar installation for 5 hours daily charging, with the purpose of selling back energy to the grid (not classified as self-consumption). Now also realize that since this is aggregate throughput, all the charging, smoothing, and then discharging to the grid takes 2x the throughput. How many days warranty do you end up getting from this '10 year warranty'? 18 MWh / (6 KWh * 5 * 2) = _300 days_.
Finally, the warranty specifically says how they may choose your compensation. Could be an outdated refurbished model, but could also be cash market value of a similar system at the date of claim. Given the exponential rate of dwindling costs for energy storage, that's a gamble that in a few years your warranty may just pay out a tiny fraction of what you originally invested in you were sold a lemon.
Tying the luxury price premium to guarantees feels very reminiscent of smartphone insurance... which is almost never a good buy. I'm with parent, let's just be honest here: you're paying for luxury markup -- sexy compact design and a good story.
I wasn't disagreeing with you... it is a luxury: peace of mind, being a patron of quality engineering, and having someone to call when shit breaks. Plus, good marketing helps. Seems like a good business strategy to me...
You guys do realize that most of the technology you buy is already made in China so its not like buying "American" is going to be some magical guarantee of quality. You'll find that a lot of the tech companies already have their products manufactured entirely overseas where the price is then marked up several hundred percent and sold to western consumers.
Regarding costs: I didn't factor in every possible cost but I still find it hard to believe that these high powered lithium batteries will work out to be cheaper than AGM batteries at this stage -- even factoring in things like shipping and installation costs (though I may be wrong about this, I think that this battery is likely to be like the Apple of PC components.)
By the way: If anyone is interested in suppliers have a look at companies like Guangzhou Henda Power Ltd and Guangzhou ESG New Energy Technology Co. They sell cheap AGM batteries like the ones I've mentioned. And you may even bump into one of SolarCity's suppliers if you do enough research ;)
Anyway, thanks for the downvotes for not band wagoning but none of you have any clue what you're doing.
So I used the calculator on Tesla's web site, in my case, I'd want 3 powerwalls and I'd want a solar installation to complement it: $18,000 USD.
That's still way too high: $1,800 - $2,500 would have been acceptable. That is how much I'm willing to pay for some solar panels, three batteries, and a little bit of electronics (processed sand) to control the lot.
As far as I'm concerned, this is all still hype. Prices need to go down, waaayyy down, and the profit margin and the engineering needs to be recuperated through volume. The days of fat profit margins and the early adopters amortizing the research and development have come and gone. The computer industry learned that lesson the hard way; it would be a shame if Mr. Musk repeated the same mistake, instead of learning from history.
A more interesting metric might be months of pay back time. $1,800-$2,500 seems like an arbitrary number you made up.
Like if your power bill averages $150 (I realize it probably doesn't) and you plan to stay in place for a few years, then something like 50*$150=$7500 is easy to consider and is much higher than the numbers you tossed out (that's just over 4 years to pay you back).
I mean, I agree with the point you are implying, that people won't be overwhelmingly excited with solar until the payback goes below 2 or 3 years, but I think it also makes sense for longer payback times.
A more interesting metric might be months of pay back time. $1,800-$2,500 seems like an arbitrary number you made up.
It is an arbitrary number I made up!
Which part of that is how much I am willing to pay requires additional clarification?
I mean, I agree with the point you are implying, that people won't be overwhelmingly excited with solar until the payback goes below 2 or 3 years,
That's exactly right, and more: I am not willing to amortize their research and development costs outright. That's something Tesla (or any other company, for that matter) will have to do over years, at least as far as my wallet is concerned. Amortizing research & development costs outright is just pure greed; I won't support it.
My point is that this is not really a good way to make financial decisions. If you've bought a house and plan to stay, spending up front to save over a decade is something to work at. Consider the rule of 72. Something that pays back in 10 years is yielding a roughly 7% return. That's a great return. As I said, I'm right there with ya on waiting until it makes good financial sense to make such purchases, I just think it is also a good idea to do some analysis to figure out what that means (and if the purchase makes sense, who cares what it means to the company selling).
On the website[0] they put for sizing 10kWh/day/BR. Which means 14600kWh/year for a 4 bedroom house. Here in Germany, working from home with a 4BR+office house, we are using 2550kWh/year. So, I suppose the Tesla sizing is to support a "peak day" usage, but still, I am surprised by the calculations. This is why this totally informal and unscientific survey :)
[0]: https://www.tesla.com/powerwall