Battery Backup Calculator

It depends on which appliances you run. A Tesla Powerwall 3 (13.5 kWh) powers essential loads like a refrigerator, lights, and Wi-Fi for 36-48 hours. Running air conditioning drops that to 3-5 hours. Use our calculator above to see exact backup times for your specific appliance mix.

The FranklinWH aPower 2 has the largest capacity at 15 kWh and 10 kW continuous power, giving it the longest backup time and the ability to run the heaviest loads. The Tesla Powerwall 3 (13.5 kWh, 11.5 kW) is a close second with higher peak power for motor starts.

For essential loads (fridge, lights, internet, phone chargers), yes — any battery in our lineup handles that. For whole-home backup including AC, dryer, and EV charger, you typically need 2-3 batteries or the FranklinWH aPower 2 which has 15 kWh capacity and 10 kW continuous power.

The battery will either trip its internal breaker or shed loads to protect itself. For example, the Enphase IQ 5P has a 3.84 kW continuous rating — running a 3.5 kW central AC plus a 1.2 kW microwave (4.7 kW total) would overload it. Our calculator flags these overload scenarios for each battery.

No. Section 25D (the residential clean energy credit) expired December 31, 2025. There is no federal tax credit for standalone battery purchases in 2026. However, batteries installed through a Propel lease (Section 48/48E) may benefit from the commercial ITC, which the financing company claims — not the homeowner directly.