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Balcony Solar Battery Calculator

A battery stores the midday solar you can't use right away and gives it back in the evening. See how much it would capture and whether it pays for itself.

How the battery calculator works

1. We estimate your kit's yearly output from your state's sunlight and the placement you choose.
2. The share you don't use yourself is the solar exported unused. Divided by 365, that's the average surplus per day.
3. A battery big enough to hold that daily surplus (allowing for charging losses) lets you use it later instead. The extra savings are that recovered energy × your electricity price.

When a battery makes sense

• Your home is empty during the day, so much of the solar would otherwise be exported unused.
• Your electricity is expensive — California, New England, Hawaii — or your utility charges more in the evening (time-of-use rates).
• You want backup power for outages. That's a real benefit our payback number doesn't count.

If you already use most of your solar during the day, a battery mostly adds cost. Often the better first step is to shift laundry, dishwashing or charging to midday. Make sure any battery connected to your home wiring is certified and allowed under your state's plug-in rules.

Frequently asked questions

Last updated October 6, 2026.