Off-Grid Solar Calculators

Appliance-specific

CPAP Machine Battery Run Time

A ResMed AirSense 10-class machine is often about 30–40 W without humidification and about 50–55 W with a humidifier. Eight hours at 53 W is already 424 Wh before inverter losses. A DC converter avoids that extra idle.

Inputs

W

≈53 W is a typical AirSense 10 with humidifier; 30–40 W without.

h

System voltage of the battery or series string.

Usable fraction of rated capacity.

Results

Energy per night
471Wh
Energy for all nights
471Wh
Battery capacity
41Ah

Recommended gear

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). A ResMed AirSense 10-class machine is often about 30–40 W without humidification and about 50–55 W with a humidifier.

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. Humidification can add on the order of 15–25 W. Eight hours at +20 W is +160 Wh, which is a large share of a small van battery. Heated tubes add more.

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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