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Battery Sizing Calculator
Estimate the usable kilowatt-hours you need from the loads you want to back up, using each load's watts and run hours.
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.
Usable kWh needed sums each load's watts multiplied by its hours, divided by 1,000. Add a margin above this figure and account for round-trip losses, since a battery does not deliver 100 percent of its rated energy. Real backup needs depend on your actual loads and outage length.
- 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.