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Backup Runtime Calculator
Estimate how many hours a battery runs from its usable capacity and your average continuous load in watts.
Screening estimate only.A licensed electrician or battery installer is authoritative for final capacity, backup panel design, and installation.
Screening result
Fine Print and Sources
Screening estimate only. These tools use only the values you enter and simple planning math. A licensed electrician or battery installer is authoritative for final capacity, backup panel design, and installation. Confirm the numbers with a professional and get written quotes.
Runtime hours equal usable capacity in watt-hours divided by the average load in watts. Real runtime is shorter because of inverter losses, surge draw, temperature, and loads that cycle on and off. Usable capacity is less than rated capacity.
- US Department of Energy, battery backup for your home: explains that home battery sizing depends on the loads you want to back up and how long you want to run them.