Off-Grid Solar Calculators

Appliance-specific

CPAP Machine Battery Run Time

A ResMed AirSense 10-class machine draws roughly 8–20 W without humidification — ResMed’s battery guide lists 0.70–1.66 A at 12 V from 6 to 20 cmH₂O — and about 30–55 W once the humidifier runs. Eight hours at ResMed’s 53 W typical figure is already 424 Wh before inverter losses. A DC converter avoids those losses and the inverter’s idle draw.

Inputs

Units
W

≈53 W is a typical AirSense 10 with humidifier; about 8–20 W without (ResMed, 12 V).

h

System voltage of the battery or series string.

Usable fraction of rated capacity.

Terms of Service

Results

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Engineering methodology

Energy per night = (CPAP watts × hours) ÷ inverter or converter efficiency. Total watt-hours = energy per night × nights. Battery amp-hours = total Wh ÷ (voltage × DoD). Set efficiency to 1.0 for a DC converter (no inverter) when the watts are the draw at the battery. A ResMed AirSense 10-class machine draws roughly 8–20 W without humidification (ResMed lists 0.70–1.66 A at 12 V) and about 30–55 W with the humidifier; 53 W is ResMed’s typical figure with humidification. Inverter idle draw is not included.

Frequently asked questions

How many watt-hours is an 8-hour CPAP night with humidifier?

At 53 W and a 90% inverter: (53 × 8) / 0.9 ≈ 471 Wh. On 12 V LiFePO4 at 95% DoD that is about 41 Ah rated. A DC converter at 100% efficiency would be 424 Wh.

Does a CPAP humidifier change battery size a lot?

Yes. An AirSense 10-class machine draws roughly 8–20 W without humidification and about 30–55 W with it, so the humidifier can add 20–35 W. Eight hours at +25 W is +200 Wh, which is a large share of a small van battery. A heated tube adds more on top.

Is this medical advice for sleep apnea off-grid?

No. Pressure, leaks and altitude change draw. Confirm your power-supply rating and keep backup capacity. This is energy math only.

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