CPAP tools

CPAP Battery Runtime Calculator

For camping, travel or power outages, the key numbers are the battery capacity in watt-hours (Wh) and how much power your CPAP draws on average. Heated humidification and heated tubing use far more power than the blower alone, so many people turn them off on battery. Running through an AC inverter wastes some energy, so a DC cable is usually more efficient. Enter your numbers to estimate runtime.

Battery capacity (Wh) Average CPAP power draw without humidifier (W) Extra average draw from humidifier and heated tube (0 if off) (W) Connection Usable share of the battery (%)

Total average draw W

Energy delivered to the CPAP Wh

Estimated runtime

Nights of 8 hours nights

How it works

Runtime (h) = battery Wh x usable share x conversion efficiency / average watts. For example, 99 Wh x 0.90 x 0.90 / 12 W.

Example

A 99 Wh battery, 90 percent usable, on a DC cable (90 percent efficient), with a 12 W average draw and humidifier off: 99 x 0.9 x 0.9 = 80.2 Wh delivered, / 12 W = 6.7 hours.

Assumptions and limits

Average draw is the most uncertain input. It depends on the model, pressure, leak and humidity settings. The 12 W default is only an example; use your manufacturer's battery guide or measure with a watt meter.
Do not confuse average draw with the rating on the power supply, which is a maximum and is much higher.
Conversion efficiencies and the usable share are typical round numbers, not measured values; cold weather and battery age also reduce capacity.
For flights, the FAA allows lithium batteries up to 100 Wh in carry-on bags, and 101 to 160 Wh with airline approval; spare lithium batteries cannot go in checked bags.
If you rely on CPAP, have a backup plan for long outages and ask your clinician what to do if you cannot use it.

Frequently asked questions

Why does the humidifier drain the battery so fast?

Heating water and a heated tube takes far more power than spinning the blower. Manufacturers' battery guides typically show runtime dropping sharply with humidification on, which is why many travel setups run without it.

Can I use any power bank?

It needs the right output for your machine (often a specific DC voltage), enough capacity and the correct cable or adapter. Check your CPAP manufacturer's list of compatible batteries and converters.

Can I bring a CPAP battery on a plane?

Lithium ion batteries up to 100 Wh can go in carry-on baggage; 101 to 160 Wh need airline approval; larger ones are generally not allowed on passenger planes. Spare batteries must be carried in the cabin with terminals protected.

Sources

Tools and screening scores are general information. They cannot diagnose or rule out a sleep disorder. Read our medical disclaimer.