What size solar battery do I need?
Last updated 1 October 2026
The quickest honest starting point is your quarterly electricity bill. A bigger bill usually means more daily usage, which usually means a bigger battery makes sense, within reason.
| Quarterly electricity bill | Usable capacity to consider |
|---|---|
| Under $300 | Around 8 kWh |
| $300 to $600 | Around 10 kWh |
| $600 to $900 | Around 13 kWh |
| $900 or more | Around 16 kWh |
This is a starting point, not a quote. Your actual best fit depends on your household's own usage pattern, not just the bill total.
The method and assumptions
A home battery is sized to cover the electricity you'd otherwise buy from the grid in the hours your solar isn't generating, mainly evenings and overnight. Working backward from a bill:
- Your quarterly bill implies a rough average daily electricity use.
- Only part of that daily use happens after the sun goes down, typically somewhere between a third and just over half of it, depending on the household.
- The battery only needs to be big enough to cover that overnight share, not your whole day's usage.
The table above reflects that reasoning for a typical home already on solar. If you don't have solar yet, or you want the battery to also cover blackouts, you'd usually want to size up from the table.
Common questions
Is this the same as a real quote?+
No. It's a rough starting point based on your bill alone. BatteryMe's full assessment asks a few more questions about your home and usage, then gets you a real installed price from a participating installer's rate card for the specific system that fits.
What if I don't have solar panels yet?+
You can still size a battery, but without solar generation to charge it during the day, it typically needs to be larger to cover the same overnight usage, or you'd pair it with a new solar system.
Does a bigger battery always mean bigger savings?+
Not necessarily. Once a battery is big enough to cover your typical overnight usage, extra capacity mostly sits unused on an average day, it only pays off further if you specifically want more blackout backup or you use well above average power overnight.