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Inverter Runtime Calculator

Calculate how long an inverter can run a load from a battery bank.

About Inverter Runtime Calculator

Inverter standby consumption matters disproportionately at light loads: a 20 W standby draw is trivial against 800 W but dominates a 50 W night-time load. Off-grid systems often lose more energy to inverter standby overnight than to the actual loads, which is why sleep modes exist.

Formula

Inverter Runtime

Runtime = usable kWh × 1,000 ÷ (load ÷ efficiency + standby draw)

standby draw
Inverter self-consumption, significant at light loads

Worked example

With the default values below, Inverter Runtime Calculator returns Runtime of 9.657. Change any input above and every figure here is recalculated in your browser.

Inputs used

Battery capacityminimum 0 kWh
10 kWh
Usable depth of dischargeaccepts 0–100 %
85 %
Loadminimum 1 W
800 W
Inverter efficiencyaccepts 0–100 %
93 %
Inverter standby drawminimum 0 W
20 W

Results

Runtime
9.657 h
Usable Energy
8.5000 kWh
Total Draw Including Standby
880.22 W
Share Consumed by Standby
2.27%
Runtime
0.402 days

Step by step

  1. 1Values used
  2. 2Inverter Runtime
  3. 3Runtime= 9.657 h
  4. 4Usable Energy= 8.5000 kWh
  5. 5Total Draw Including Standby= 880.22 W
  6. 6Share Consumed by Standby= 2.27
  7. 7Runtime= 0.402 days

Assumptions and limits

  • The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Inverter Runtime calculated?

Runtime = usable kWh × 1,000 ÷ (load ÷ efficiency + standby draw) Inverter standby consumption matters disproportionately at light loads: a 20 W standby draw is trivial against 800 W but dominates a 50 W night-time load.

Why does Inverter Runtime matter?

Off-grid systems often lose more energy to inverter standby overnight than to the actual loads, which is why sleep modes exist.

What values do I need to enter?

This calculator takes 5 inputs: Battery capacity, Usable depth of discharge, Load, Inverter efficiency, Inverter standby draw. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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