A battery saves money only if it turns solar you'd export at a low credit into evening power worth the full retail rate. Enter your solar system and battery size to see whether that happens in your state, and which battery size gives the best payback.
Same solar system and rates as above. A battery can only store solar you would otherwise export, so payback stays about the same as you add capacity until the battery outgrows your surplus solar; after that, extra capacity adds cost but no savings. The highlighted row is the largest size before that happens.
The 0.90 is round-trip efficiency, 300 cycles a year assumes a battery cycles on most days, and capacity fades 2% a year. Default battery prices come from the same state cost data used on our battery cost pages, and defaults for rate, sun hours and export credit match our solar payback calculator.
Backup power has real value that is not converted to dollars here. Time-of-use arbitrage beyond the evening premium field, demand charges, financing interest and battery replacement are also excluded, and the federal credit is not applied because it ended for systems placed in service after 2025. Use the result to compare options, then check against written quotes. For sizing a battery for outages instead of savings, see the Battery Backup Runtime Calculator.
From bill savings alone, only when your utility pays much less for exported solar than it charges for power. If your export credit is close to the retail rate, a battery adds little savings, and its value is backup power instead. This calculator shows which case you're in.
A battery moves solar you would have exported into the evening, where it offsets the full retail rate. The gain per kWh is the retail rate minus what exports were worth, minus about 10 percent lost to round-trip efficiency. Under full retail-rate net metering that gain is zero or negative.
No. Outage protection has real value but varies by household, so it is not converted into dollars here. Compare the payback with how much you would pay for backup alone. There is no federal credit applied, since the residential credit ended for systems placed in service after 2025.