I saw this post about Panasonic’s home battery. The claim is that this will lead a battery that can power a house for a week. I wonder if I can estimate how big this battery would be.

First – to estimate the energy a house consumes. My first approximation is that you could probably run a house off of a 5000 Watt generator, but this probably isn’t the average power use for a house. It is probably lower. I am going to go with an estimate of 2000 Watts as the average power over 1 day. How much energy would this be for 1 week?

The article above claims that it is a lithium ion battery. According to Wikipedia, the energy density of a lithium-ion battery is on 0.46-0.72 MJ/kg. For the purposes of this calculation, I am going to go with an energy density of 0.8 MJ/kg. I can calculate the mass of this house battery as:

This is around 3000 lbs. Of course, this calculation assumes a 100% efficient battery – or maybe that is already taken into account into the wikipedia energy density. Anyway, even at 3000 lbs, this is possible for a house, right? How big would it be? The wikipedia page lists the volume energy density as 0.9 MJ/L, so this would make the volume:

This isn’t too bad – like the volume of a small refrigerator.

I, for one, welcome such a battery. Even without solar panels or something, this would be awesome for the cases where we lose power in the house.

### Update

I made some changes thanks to commenter Emory K (Emory K gets 10 bonus points). I don’t know what I was thinking, but I said there were 24 hours in a week. Hint – that is wrong. I guess I shouldn’t blog on vacation or I am bound to make mistakes.