How big a power station a CPAP needs comes down to one number most people never look up: how many watts the machine draws through the night. ResMed’s AirSense 11 user guide lists a typical power consumption of 56.1W and a peak of 73.2W, with the machine running on a 24V DC supply. Those figures include heated humidification. With the humidifier and heated tube switched off, a CPAP typically draws far less, so the right station can be half the size. This guide works through the math night by night, with every runtime clearly marked as an estimate, so you can size a station for one night, a long weekend or a multi-day outage.
Medical note: This isn’t medical advice. Talk to your doctor, your equipment supplier and your CPAP’s manufacturer before relying on a battery for therapy, and always have a backup plan. Several power station makers state in their manuals that their units aren’t intended for life-sustaining medical equipment.
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Step 1: Find Your CPAP’s Real Draw
There are three ways to get the number, from most to least accurate:
- Measure it. Plug the CPAP into a plug-in watt meter for a full night, with your normal settings, and read the kWh in the morning. Our Kill A Watt guide shows how.
- Use the manufacturer’s figure. ResMed lists 56.1W typical and 73.2W peak for the AirSense 11. That’s a conservative planning number when humidification is on.
- Use a planning range. If you can’t measure, the table below gives reasonable ranges by setting. These are estimates; pressure, mask leak, room temperature and humidity all shift the real draw.
| CPAP setting | Planning range (estimate) | Per 8-hour night (estimate) |
|---|---|---|
| Humidifier and heated tube off, low–moderate pressure | ~10–35W | ~80–280Wh |
| Humidifier on, heated tube off | ~35–60W | ~280–480Wh |
| Humidifier and heated tube on | ~55–75W (ResMed: 56.1W typical, 73.2W peak) | ~450–590Wh |
The humidifier is the big variable. It can more than double the nightly energy use, which is why the same station might last four nights for one person and two for another.
Step 2: Decide AC or DC
A CPAP’s power brick converts 120V AC down to DC. The AirSense 11’s runs at 24V DC, per ResMed’s guide. If you plug that brick into a power station’s AC outlet, the station first converts its battery’s DC to AC, and the brick then converts it back to DC. Each step wastes some energy, and the station’s inverter also draws power just to stay switched on.
The alternative is a DC cable or converter that runs the CPAP straight from the station’s 12V car socket. ResMed sells an Air11 DC/DC converter for this, rated for 12V or 24V input. Our inverter efficiency and idle draw guide explains the losses in detail.
| Path | Planning efficiency (estimate) | Extra overhead |
|---|---|---|
| AC outlet + CPAP power brick | ~80–85% | Inverter idle draw, often 10–25W on mid-size stations |
| 12V socket + manufacturer DC converter | ~85–90% | Small converter loss, no inverter idle |
With a 30W CPAP, a 20W inverter idle adds two-thirds again to the load. That’s why DC can almost double the number of nights on a small CPAP load. Luis’s Delta 3 Max CPAP runtime breakdown shows the same effect on a 2kWh station.
Step 3: Do the Night-by-Night Math
The formula is simple:
Nights = (station Wh × efficiency) ÷ (CPAP watts + inverter idle) ÷ hours per night
For DC, leave out the inverter idle. Here’s a worked example for a 30W CPAP (humidifier off), 8 hours a night, on a 1,000Wh station:
- AC: 1,000Wh × 0.85 = 850Wh usable. 850 ÷ (30W + 15W idle) = ~19 hours = about 2.4 nights.
- DC: 1,000Wh × 0.88 = 880Wh usable. 880 ÷ 30W = ~29 hours = about 3.7 nights.
Same station, same CPAP, more than one extra night just by skipping the inverter.
Nights by Station Size
All figures below are our estimates for 8-hour nights. AC assumes 85% efficiency and a 10W idle on small stations (15W on 1kWh, 20W on 2kWh). DC assumes 88% efficiency.
| Station capacity | 30W CPAP, AC | 30W CPAP, DC | 55W CPAP (humidifier on), AC | 55W CPAP, DC |
|---|---|---|---|---|
| 256–300Wh | ~0.8 night | ~1.1 nights | ~0.5 night | ~0.6 night |
| 500Wh | ~1.3 nights | ~1.8 nights | ~0.8 night | ~1 night |
| 1,000Wh | ~2.4 nights | ~3.7 nights | ~1.5 nights | ~2 nights |
| 2,000Wh | ~4.3 nights | ~7.3 nights | ~2.8 nights | ~4 nights |
| 3,000Wh+ | ~6.4 nights | ~11 nights | ~4.2 nights | ~6 nights |
Two takeaways. First, a station around 300Wh is a one-night tool, and only if you use DC with the humidifier off. Second, if you need humidification for several nights, you’re looking at 1kWh or more.
Matching the Station to the Situation
One night of camping
A compact station around 300Wh works with the humidifier off and a DC cable. Luis reviewed the 288Wh BLUETTI Elite 30 V2 powering a Starlink Mini and a Mac (not a CPAP). At about 9.4 lb with a 600W inverter, per BLUETTI, it’s the kind of compact station that fits this one-night role. Pack the station fully charged; you’ll have little margin.
A long weekend (two to three nights)
Aim for 1,000Wh, or 500Wh plus a solar panel you can set out during the day. With the humidifier on, plan on 1,000Wh plus solar. Our CPAP camping guide covers airline rules and camp setup.
A multi-day power outage at home
A 2,000Wh station gives most people four or more nights on DC with the humidifier off, and two to three with it on over AC. If the outage might run longer, add a way to recharge: solar panels, a car charger or a generator.
Solar Top-Ups
A CPAP uses most of its energy at night, which suits solar charging during the day. As a rough guide, a 100W panel often delivers 300–500Wh on a clear day once you account for heat, angle and haze. That’s enough to replace one night of a 30W CPAP on DC, with some left over. With the humidifier on, plan on 200W of panels. These are estimates; Luis’s own 60W panel measured about 35–40W in direct sun, which shows how far below the label real output can land.
Small Changes That Add Nights
- Turn off the heated tube when the room isn’t cold. It’s often the largest add-on after the humidifier.
- Lower the humidity setting instead of turning it off entirely if dryness bothers you.
- Use DC whenever possible. It skips the inverter’s idle draw entirely.
- Switch off the station’s AC output if you’re running on DC, so the inverter isn’t idling.
- Keep the station warm. Batteries deliver less in the cold, and many won’t charge below freezing.
- Check your mask fit. A leaking mask makes the machine work harder.
Test Before You Depend On It
Whatever size you choose, do a full dress rehearsal at home before a trip or storm season:
- Charge the station to 100% and note the percentage display.
- Run the CPAP from it overnight with the exact settings you’ll use, on the same AC or DC path.
- In the morning, check the remaining percentage. Divide 100 by the percentage used to get your real nights per charge.
- Confirm the station didn’t auto-shut off its output during low-draw periods. Some stations turn off AC or DC ports when the load drops very low, so check your manual for any timeout setting.
- Keep the CPAP’s original wall adapter with you in case you need to switch back to grid power.
One night of testing tells you more than any table, including this one.
FAQ
What size power station do I need for a CPAP?
For one night with the humidifier off on DC, about 300Wh. For two to three nights, or one night with the humidifier on, about 1,000Wh. For multi-day outages, 2,000Wh or more. These are our estimates; measure your machine for a better number.
How many watts does a CPAP use?
ResMed lists the AirSense 11 at 56.1W typical and 73.2W peak. Without heated humidification, many CPAPs draw well under that, often in the 10–35W range.
Is it better to run a CPAP on AC or DC?
DC is usually more efficient because it avoids the inverter’s conversion losses and idle draw. Use the DC converter or cable your CPAP’s manufacturer approves.
Can a 300Wh power station run a CPAP all night?
Usually, if the humidifier is off and you use DC. With the humidifier on, a 300Wh station may not last a full 8 hours.
How do I know my CPAP’s exact power use?
Run it overnight through a plug-in watt meter and read the kWh in the morning. That captures your actual pressure and settings.
Can I charge the power station while using the CPAP?
Many stations support pass-through charging, but check your station’s manual. Some makers note that charging and discharging together generates more heat.
Bottom Line
Start with your CPAP’s real draw, decide whether you can run it on DC, then multiply by the nights you need. Humidifier off on DC, a 300Wh station covers one night and 1,000Wh covers about three. Humidifier on over AC, double the capacity. If the numbers are tight, a solar panel or a car charger buys extra nights. Luis’s watt-meter test of a CPAP with the humidifier on and off is planned and will add measured figures here.
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