I have not tested these units. Every figure below is sourced from manufacturer specifications, published measurements, or user reports — and cited. How I research this.
Medical disclaimer: I am not a doctor. Nothing here is medical advice. Decisions about your therapy settings — including whether to turn off humidification — belong with your sleep physician, not with a website. This article is about electricity, not treatment.
The number almost nobody tells you
Your CPAP blower motor is not the problem. It draws around 10 to 25 watts, depending on your prescribed pressure — roughly the same as a phone charger.
The heated humidifier is the problem. Its heating element accounts for roughly 15 to 25 watts on its own. The heated tube adds another 10 to 15 watts.
That means the same machine can draw 25W or 65W depending entirely on settings you control.
Over an eight-hour night, that difference is roughly 200Wh versus 520Wh — the gap between a battery that costs $300 and one that costs $900.
Real numbers, not label numbers
The wattage printed on your power supply is a maximum rating, not what the machine actually pulls. ResMed lists a 65W power supply for the AirSense 11; real-world draw is usually well below that.
One CPAP user who measured their own machine with a proper meter over a full night reported a maximum draw of 67W and an average of about 45W, consuming 470Wh total — and that was with humidification running in a dry climate at altitude, which they described as close to a worst case.
The lesson: measure your own setup if you can. A $20 plug-in power meter will tell you more than any article, including this one.
Planning ranges
| Setup | Typical draw | 8-hour need |
|---|---|---|
| Travel CPAP, no humidifier | 6–27W | ~50–220Wh |
| Standard CPAP, humidifier off | 20–40W | ~160–320Wh |
| Standard CPAP, humidifier on | 40–65W | ~320–520Wh |
| High heat, heated tube | 65–100W+ | ~520–800Wh |
Ranges compiled from ResMed published specifications, manufacturer documentation, and measured user reports. Your machine will differ.
The formula
You do not get 100% of a battery’s rated capacity. The inverter loses energy converting DC to AC.
Runtime (hours) = Battery Wh × 0.70 ÷ your CPAP watts
Use 0.70 when plugging into a standard AC outlet on the power station. If your machine supports a manufacturer-approved DC adapter, use 0.85 instead — you skip a conversion step and keep more of the energy.
Worked example: a 1,000Wh station running a 45W CPAP over AC gives roughly 1,000 × 0.70 ÷ 45 = about 15 hours. Comfortably one night, with reserve.
The same station running a 90W setup gives about 7.8 hours — cutting it close on a full night, with nothing left over.
What size do you actually need?
| Your situation | Capacity |
|---|---|
| One night, humidifier off | 300–500Wh |
| One night, humidifier on | 700–1,000Wh |
| Two nights, humidifier off | 700–1,000Wh |
| Two nights, humidifier on | 1,500–2,000Wh |
| Multi-day storm, want reserve | 2,000Wh+ |
Note what is not in this table: output wattage. Almost every power station on the market can supply 45W. You are buying capacity, not output. Do not let a salesperson upsell you on a 3,000W inverter you will never use.
The feature that actually matters: UPS switchover
If the power fails at 2am and your CPAP simply stops, you wake up. That defeats the purpose.
Some power stations support pass-through with UPS-grade switchover — you leave the CPAP plugged into the station, the station plugged into the wall, and when the grid drops the battery takes over in under 20 milliseconds. Fast enough that the machine never notices.
Not every station has this. Many advertise “UPS” loosely. Check the published switchover time in milliseconds before you buy.
And test it yourself before you rely on it. Plug everything in, pull the wall plug, and see whether your machine stays running. Do this during the day, not during a storm.
Settings that extend runtime
In rough order of impact:
- Humidifier off — cuts roughly 30% of total draw. This is by far the biggest lever.
- Heated tube off — another 10 to 15%.
- DC adapter instead of AC — recovers roughly 15% lost to inverter conversion, if your machine supports one.
Read this part carefully. Turning off humidification will likely make your nose and throat dry. For most people this is uncomfortable but tolerable for a night or two.
For some people it is not. If you have a history of nosebleeds, severe congestion, or your physician specifically prescribed humidification, this is a conversation to have with them, not a decision to make from a website. Ask your sleep provider what emergency settings are appropriate for you, before you need them.
Where to buy
Once you know your capacity target, you are shopping for a number, not a brand. Compare Wh capacity, published switchover time, and price.
Outbound Power stocks most major brands and lists capacity and output clearly on each product page. This is an affiliate link — if you buy through it, I earn a commission at no extra cost to you. It does not change what I write. See my affiliate disclosure.
Safety notice
Sleep apnea is a medical condition and CPAP is a prescribed treatment. This article covers the electrical side only — how many watt-hours you need. It is not advice about your therapy.
Never run a fuel-powered generator indoors, in a garage, or in any enclosed space to power medical equipment. Carbon monoxide is odorless and kills. Battery power stations produce no exhaust and are the appropriate tool for indoor overnight use.
Test any backup system before you depend on it.