Depends on your jurisdiction, but roof mounted solar installs generally don't need building permits. Electrical permits on the other hand are almost always required.
If you actually want to offset cost, don't buy a portable battery pack. Get an AIO solar inverter and a server rack battery. They're generally plug and play - wire the panels to it, connect the battery.
If you want to run your home loads, the cheapest/simplest way (without going grid-tie) is to have an electrician add a critical loads panel supplied by your inverter output, then plug your inverter in to the grid for backup (in case no solar or batteries are low).
"If you want to run your home loads, the cheapest/simplest way (without going grid-tie) is to have an electrician add a critical loads panel supplied by your inverter output ..."
No, that's actually not the simplest.
Far simpler is to install a solar breaker in your main panel and a physical lockout[1] between utility power and the new solar breaker.
There is no ATX, there are no smarts, the power goes out and you flip two breakers. There is nothing simpler than this.
The beauty of this is, you can keep scaling up your solar generation, adding panels as the years go by, and you are never locked into these ridiculous "preferred breakers" sub-panels.
Will you have to be smart about your total power use while you are on solar ? Yes, you will - just don't run the dryer and the microwave at the same time.
When I mean simplest, I meant a solution that doesn't rely on doing anything. If/when Solar isn't enough or your batteries deplete, it just falls back to grid. Power outage? Your critical items automatically are backed by solar/battery.
Having to think about your what high draw appliances are running and using additional power adds mental load (ie complexity) and is an immediate no for most people.
Changing your usage pattern is ultimately at the heart of any serious proposal for solving energy scarcity. We have enough energy to power our civilisation without catastrophe: we're just using it in an extremely inefficient manner.
cheapest/simplest way (without going grid-tie) is to have an electrician add a critical loads panel supplied
Cheaper way is have electrician wire a manual transfer switch at the existing panel. When you loose power, turn off non-essential breakers and then flip transfer switch.
You lose all benefits of solar/battery except for during a power outage and you have to flip all your breakers? (you also won't immediately know when the power is back).
Might as well save money and not install anything- use an extension cord for those rare times.
Our solar inverter uses the 60hz AC from and grid to do the DC->AC conversion. The inverter stops functioning if the power is out. I thought they all did that for safety.
If you actually want to offset cost, don't buy a portable battery pack. Get an AIO solar inverter and a server rack battery. They're generally plug and play - wire the panels to it, connect the battery.
If you want to run your home loads, the cheapest/simplest way (without going grid-tie) is to have an electrician add a critical loads panel supplied by your inverter output, then plug your inverter in to the grid for backup (in case no solar or batteries are low).