20-30 year old mechanical meters tend to be pretty accurate, but when they aren't, they tend to read low. Especially if your usage is fairly low, the minimum usage to push the wheels forward may be higher than your standby loads.
If you've been on a meter that reads low for a long time, a new meter (mechanical or electronic) will be a big jump.
Mechanical meters either accurately measure use, run to slow or don't work at all. The worse thing that can happen is that other people indirectly have to pay for the missing killowatts. In contrast there are plenty of stories where people get bills 10-20 times what they are used to.
Any half decent programmer on HN knows what to do when something has almost no chance of happening.
Some of these things display only billable KWH while it isn't so expensive to display current consumption too.
You can also measure it twice so that one can (remotely) see two entirely different readings and replace the meter with one that works properly. It could also display the amount of money owed. (estimate) It would make it slightly more expensive for everyone rather than accidentally billing some people truly crazy amounts.
Just like a bank account can have a configurable limit for withdrawals the smart thing to do is to set a limit per day, week, month and have an alarm go off and/or shut everything down.
Say my monthly bill is 200, I don't want the previous 7 days to exceed 500.
Just a flashing led and a 5000 euro bill isn't smart. Imagine diagnosing a server by how fast the led flashes. Imagine replacing the speedometer in your car with a flashing light. You will know how fast you drove when the fines come in.
