How Many Watt-Hours Does a CPAP Use?
One setting on your machine roughly triples its power draw. Get that wrong and you buy a battery that dies at 3am.
The short answer
Roughly 180-400Wh per night with the heated humidifier off, and 500-900Wh per night with it on. Most CPAP machines draw 30-60W in normal operation, but a heated humidifier and heated tubing are resistive heating elements that can add 40-70W continuously. Turning the humidifier off is the single biggest thing you can do to make a CPAP practical on battery power.
This is the question where the gap between the marketing answer and the useful answer is widest. Brand blogs will tell you a CPAP 'uses very little power' — true of the blower motor, and misleading about the machine as a whole, because most people sleep with the humidifier on and have no idea it is the dominant load.
Where the watts actually go
| Component | Typical draw | Per 8-hour night |
|---|---|---|
| Blower motor, low pressure | 20-35W | 160-280Wh |
| Blower motor, higher pressure or leak | 40-60W | 320-480Wh |
| Heated humidifier | +30-60W average | +240-480Wh |
| Heated tubing | +10-20W average | +80-160Wh |
| Machine on standby | 1-3W | 8-24Wh |
The humidifier figure is an average, not a constant — it heats a water chamber to a target and then maintains it, so it cycles. It also works far harder in a cold tent than in a heated bedroom, which is precisely the situation where you are on battery.
Run it on DC if your machine allows it
This is the practical tip that changes the numbers most. Most CPAP machines are internally DC devices with an external power brick. If you run one from a power station's AC outlet, you are converting the battery's DC to AC in the inverter, then back to DC in the brick — paying a conversion penalty twice, often 10-20% in total.
Many manufacturers sell a DC cord that runs the machine directly from a 12V socket, skipping both conversions. It is a modest saving in percentage terms and a meaningful one when your battery is only just big enough. It also means the power station's inverter stays off overnight, which is quieter and avoids the idle draw of the inverter itself — a real cost on some units.
What size to buy
- One night, humidifier off, weight matters — around 300Wh. That is the smallest honest answer, and it is genuinely portable at about 10 lb.
- Two to three nights, humidifier off — 1,000Wh, which is the standard camping size anyway.
- Multiple nights with the humidifier on — you want 2,000Wh or a solar panel, and realistically both. This is the case where solar stops being optional.
- Home backup during an outage — add the CPAP's nightly figure to your fridge and router load. See what size for a power outage.
For the units and trade-offs specifically, best power station for CPAP camping covers the picks. And if you are flying to your trip rather than driving, read the plane rules first — medical devices get some accommodations, the batteries that power them mostly do not.
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