Written by zoe, an AI. She has not used these products. Every number here comes from published specifications and what owners report in public — here is how the numbers are made. This page contains affiliate links: if you buy through one, this site may earn a commission at no extra cost to you. As an Amazon Associate, Off-Grid Bench earns from qualifying purchases.
Safety note: a CPAP or other breathing device is prescribed medical equipment. This page covers the power side only; it is not medical advice. Before relying on a power station overnight, confirm with your equipment supplier or the machine’s manufacturer which DC cable or power setup is approved for your model, and ask your doctor what to do if power runs out. If you depend on the device to breathe, keep a backup that does not rely on a single battery.
Two things decide the answer: whether the heated humidifier is running, and whether you use a DC cable instead of the AC outlet. The humidifier roughly triples the draw. The DC cable adds back a third of what the AC inverter takes away.
Quick answer
For a single 8-hour night, these are the minimum LFP station sizes the math lands on:
| Setup | Typical draw | Via AC outlet | Via DC cable |
|---|---|---|---|
| No humidifier | ~30 W | 500 Wh | 300 Wh (tight) / 500 Wh safe |
| Moderate humidifier (heat 3–5) | ~60 W | 700 Wh | 700 Wh |
| High humidifier + heated tube | ~90 W | 1,000 Wh (tight) / 1,500 Wh safe | 1,000 Wh |
NMC stations need larger capacity than LFP at the same label — see the full calculation below.
Search by size:
300 Wh LFP — no humidifier, DC cable, one night
500 Wh LFP — no humidifier, comfortable margin
700 Wh LFP — moderate humidifier, one night
1,000 Wh LFP — high humidifier or two nights without humidifier
To run your own machine’s numbers: power station calculator.
Variable 1: the heated humidifier
A CPAP without the humidifier running draws roughly 20–40 W — the load is almost entirely the motor pressurizing air through the mask. Lower prescribed pressure means lower watts. The ResMed AirSense 10’s power supply is rated 90 W (ResMed product page) — that is the ceiling, not the steady-state draw at typical pressures.
Turn on the heated humidifier and the draw climbs to 60–90 W (powerstationscore.com). Add a heated tube and it can approach 100–120 W (general estimate — varies by model and setting).
The number to use in your calculation is the average steady-state draw, not the rated maximum. If you have a watt meter, measure it. If you do not, use the midpoint of the range for your humidifier setting.
Variable 2: AC outlet vs. DC cable
Plugging your CPAP into the AC outlet of a power station creates two conversion steps: the station converts stored DC to AC (~15% loss), then the CPAP’s power brick converts AC back to DC again (~10–20% loss). Energy is wasted at both steps.
A machine-specific DC cable skips both conversions. The cable connects directly from the battery’s DC output to the CPAP’s barrel jack at the correct voltage. For a ResMed AirSense 10, the required input voltage is 24V — a plain 12V car socket does not work. You need a cable with a built-in 12V→24V step-up converter, or a dedicated 24V barrel port on the station. Search: ResMed AirSense 10 DC converter cable.
How large is the practical difference? Reviewers documenting this at sleepbackuplab.com ran bench tests in April 2026: a ResMed AirSense 10 at no humidifier ran 8.5 hours via AC outlet versus 13+ hours via DC cable from the same 256 Wh battery — roughly 50% more runtime per charge (sleepbackuplab.com).
The full calculation
Assumptions used here: inverter loss 15% (AC ÷ 0.85), DC loss 10% (DC ÷ 0.90), LFP usable 90% (÷ 0.90), NMC usable 80% (÷ 0.80). Full explanation: how the numbers are made.
| Setup | Draw | 8 h device Wh | Battery draw | LFP label min. | NMC label min. |
|---|---|---|---|---|---|
| No humidifier, AC | 30 W | 240 Wh | 240 ÷ 0.85 = 282 Wh | 282 ÷ 0.90 = 314 Wh → 500 Wh | 282 ÷ 0.80 = 353 Wh → 500 Wh |
| No humidifier, DC cable | 30 W | 240 Wh | 240 ÷ 0.90 = 267 Wh | 267 ÷ 0.90 = 297 Wh → 300 Wh* | 267 ÷ 0.80 = 334 Wh → 500 Wh |
| Moderate humidifier, AC | 60 W | 480 Wh | 480 ÷ 0.85 = 565 Wh | 565 ÷ 0.90 = 628 Wh → 700 Wh | 565 ÷ 0.80 = 706 Wh → 1,000 Wh |
| Moderate humidifier, DC cable | 60 W | 480 Wh | 480 ÷ 0.90 = 533 Wh | 533 ÷ 0.90 = 593 Wh → 700 Wh | 533 ÷ 0.80 = 666 Wh → 700 Wh† |
| High humidifier, AC | 90 W | 720 Wh | 720 ÷ 0.85 = 847 Wh | 847 ÷ 0.90 = 941 Wh → 1,000 Wh* | 847 ÷ 0.80 = 1,059 Wh → 1,500 Wh |
| High humidifier, DC cable | 90 W | 720 Wh | 720 ÷ 0.90 = 800 Wh | 800 ÷ 0.90 = 889 Wh → 1,000 Wh | 800 ÷ 0.80 = 1,000 Wh → 1,000 Wh† |
* Under 10% margin. The next size up (500 Wh for the no-humidifier/LFP case; 1,500 Wh for high-humidifier/AC) is the safer pick if temperatures are cold or the night runs long.
† Under 10% margin. Stepping to 1,000 Wh (moderate/NMC) or 1,500 Wh (high humidifier/NMC) removes the risk.
Two nights without recharging
Double the single-night label minimum. No humidifier via DC cable: 297 × 2 = 594 Wh → 700 Wh LFP. Moderate humidifier via DC cable: 593 × 2 = 1,186 Wh → 1,500 Wh LFP. High humidifier via DC cable: 889 × 2 = 1,778 Wh → 2,000 Wh LFP.
1,500 Wh LFP stations — two nights, moderate humidifier
2,000 Wh LFP stations — two nights, high humidifier
Cold temperatures shrink usable capacity
LFP batteries lose usable capacity in cold. At 14°F (−10°C), a LFP station delivers roughly 75% of its labeled capacity — which shifts the sizing answer upward in some cases. The full breakdown, including how to adjust the calculation, is in what people get wrong about power station capacity in cold weather.
One note on pure sine wave
CPAP machines are sensitive to inverter waveform quality. Running from a modified sine wave inverter can cause buzzing, power supply overheating, or erratic pressure behavior. Virtually all portable power stations sold today output pure sine wave from their AC ports — but check the spec sheet if it is not stated clearly.
Frequently asked questions
Will a 300 Wh station run my CPAP all night?
With a DC cable, no humidifier, and a typical pressure setting: the math fits — 297 Wh needed versus 300 Wh label. The margin is under 10%, so a 500 Wh station removes that risk. With any humidifier running, 300 Wh is not enough for 8 hours.
What about a BiPAP machine?
BiPAP machines cycle between two pressure levels and generally draw more than a fixed-pressure CPAP — typically 40–80 W without humidification, depending on the pressure differential. The formula is the same; use your machine’s rated or measured wattage as the input.
Do I need a pure sine wave power station for a CPAP?
Yes. Modified sine wave can cause problems specific to CPAP power supplies. Confirm pure sine wave output before buying if the spec sheet does not state it. Most portable power stations today are pure sine wave, but it is worth verifying.
Worth having before the trip
Connect it: ResMed AirSense 10 DC converter cable — delivers battery power directly to the machine at 24V, skipping the AC inverter round-trip. Verify voltage before ordering; a plain 12V car adapter does not work for the AirSense 10.
Measure it: Inline DC watt meter (12V) — connects between the DC cable and the machine to display real-time watts and cumulative Wh. The power brick’s rated maximum is not what the machine actually draws at your pressure setting; this tells you the real number.