Off-Grid Solar Calculators

Inverters and charge controllers

Inverter Idle Draw Battery Drain

Many 2000 W inverters idle at 15–25 W. Left on all night that is 200–400 Wh — more than a laptop. Switch the inverter off, use a DC load, or pick a unit with a low search/idle mode.

Inputs

W
h

System voltage of the battery or series string.

Usable fraction of rated capacity.

Results

Energy wasted
200Wh
Equivalent battery capacity
17.5Ah

Rated amp-hours you would need just to cover this idle, at the chosen DoD.

Recommended gear

Engineering methodology

Energy wasted = idle watts × hours (Wh = P × t). Equivalent battery amp-hours = watt-hours ÷ (voltage × DoD), from Wh = Ah × V. DoD converts wasted energy into the rated capacity you would need just to cover idle. Measure idle at the DC input if you can.

Frequently asked questions

How much battery does a 20 W inverter idle use overnight?

20 W × 10 h = 200 Wh. On a 12 V LiFePO4 bank at 95% DoD that is about 17.5 Ah of rated capacity—before any real AC load.

Does search or power-save mode change idle draw?

Yes. Many inverters drop well below their full idle in search mode, then wake on a load. Enter the mode you actually leave on overnight. Temperature and DC voltage also move idle watts.

Should I leave the inverter on 24/7 in a van?

Only if you need instant AC. Otherwise switch it off or use native 12 V loads. Idle can exceed a laptop’s daily energy.

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