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ENGINEERING TOOL

Battery Runtime Calculator

Estimate how long a battery can power a load from usable capacity, depth of discharge and inverter efficiency.

Battery Runtime Calculator

FREE ONLINE TOOL
Formula and assumptions

Usable energy (Wh) = capacity (kWh) × 1,000 × usable share × inverter efficiency; runtime (h) = usable energy ÷ average load (W).

Estimate only. Startup surges, temperature, battery age and voltage cutoffs affect actual runtime. Follow manufacturer limits.

1 kWh × 80% usable × 90% efficiency = 720 Wh; at 120 W, estimated runtime is 6 hours.

STEP BY STEP

How to use battery runtime calculator

  1. Check the input units and assumptions.
  2. Review the result and example.

IN PRACTICE

Example

A 1 kWh battery at 80% usable capacity and 90% inverter efficiency provides about 720 Wh. A 120 W average load runs for about 6 hours.

GOOD TO KNOW

How is estimated battery runtime calculated?

Usable energy (Wh) = capacity (kWh) × 1,000 × usable share × inverter efficiency. Runtime (hours) = usable energy ÷ average load (W). This estimate excludes startup surges, temperature effects, aging and voltage cutoffs.

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