Independent research, updated August 18, 2026. Some product links are affiliate. No test lab. How we work
Tool · average-load math only

Home battery runtime calculator

Runtime hours = (battery kWh × efficiency × usable fraction) ÷ load kW. Appliances are optional and replace a guessed household load when you switch modes — they are not stacked on top of 2.8 kW.

Runtime formula diagram
Essentials versus whole-home loads

In appliance mode this field is extra load on top of checks, default 0 if you clear it.

Efficiency & usable %
PRESETS (sets kW field, clears checks)

Limits of this tool

  • No temperature derate, no aging, no inverter clip.
  • No motor locked-rotor amps. A ½ hp well pump can demand several kW at start.
  • Refrigerator watts are a running average; compressors cycle.
  • Default 92% / 95% are conservative planning numbers, not a lab measurement of your unit.
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