How to Power a CPAP While Camping

This guide is about the power side of camping with a CPAP. It isn't medical advice. Ask your doctor or sleep clinic before you change your humidifier settings or skip therapy.

How much power a CPAP really uses

Most people look at the power brick, see 65 or 90 watts, and buy a battery for that. That's far more than a CPAP uses most of the night. The brick is sized for the worst case: high pressure, humidifier on high and a cold room.

Here are the numbers makers and sellers publish:

ResMed's power test used a typical breathing pattern at 8 to 15 cm H2O pressure with the humidifier at level 6. ResMed lists those figures as watt-hours; we read them as watt-hours for each hour of use, which is the same as average watts. Your pressure, mask leak, room temperature and humidifier setting all change the real number.

So which number do you plan with? If you've measured your own machine on a plug-in watt meter, use that. If not, our calculators use 30 W for a CPAP without a humidifier and 53 W (ResMed's typical figure) with one. Those are on the safe side of ResMed's test numbers, which is where you want to be when the thing you're powering helps you breathe.

Newer machines are a little easier on power. CPAP.com notes the AirSense 11 ships with a 65 W power supply, down from the AirSense 10's 90 W, and uses less energy.

Watt-hours per night

Watt-hours are the size of the tank. Multiply watts by hours of sleep, then account for how the power gets to the machine:

• From a power station's AC outlet: our Power Station & Solar Sizer divides by 0.85, the factor Jackery uses in its own run-time formula, to cover the losses inside the station.
• From a 12 V battery through an inverter: our Inverter Run Time Calculator divides by 0.85 for inverter efficiency and adds the inverter's idle draw. Its default is 7 W, the zero-load figure for a Victron Phoenix 12/1200, for every hour the inverter is on.

Power station column: watts × 8 ÷ 0.85. Battery and inverter column: watts × 8 ÷ 0.85 + 7 W × 8 hours. Example for the last row: 53 × 8 = 424 Wh; 424 ÷ 0.85 = 499 Wh; 499 + 56 = 555 Wh.

Notice how much the inverter's idle draw matters on a small load. For the machine-only row, the inverter just sitting there uses almost as much as the CPAP.

What size power station

Here's what our Power Station & Solar Sizer gives with just a CPAP on the list, 8 hours a night, no solar. It treats the station's full rated watt-hours as usable and recommends the next common size up.

From our Power Station & Solar Sizer: nights × energy per night, rounded up to the next size in its list (300, 500, 700, 1,000, 1,500, 2,000 Wh and up).

"Tight" means there's almost nothing left over. Stations lose capacity as they age and in the cold, so if a size is tight, go one step up. And remember anything else you plug in, like phones, lights or a 12 V cooler, comes out of the same tank. Add them in the calculator.

A few other things to check on the spec sheet:

• Outlet type. If you'll use a DC cord, make sure the station has a 12 V car-style outlet with enough amps. EcoFlow's DELTA 2, for example, lists a 12.6 V, 10 A (126 W) car outlet, which is above the AirSense 10's 104 W peak.
• Quiet. Some stations run a cooling fan under load. You'll be sleeping next to it.
• Battery type. Lithium iron phosphate (LiFePO4) stations last thousands of cycles. Jackery rates its Explorer 1000 v2 at 4,000 cycles to 70% capacity.

Compare picks on our power stations page.

Running it from a 12 V battery

If you already have a deep-cycle battery for the boat or camper, it can run a CPAP too. Here's what our Inverter Run Time Calculator gives for a 100 Ah battery through an inverter (85% efficiency, 7 W idle), 8 hours a night:

Amp-hours = watt-hours ÷ 12 V. The calculator counts 80% of a lithium battery and 50% of an AGM as usable, and adjusts for draw rate with Peukert's law (k = 1.05 lithium, 1.15 AGM). At these small draws the adjustment barely matters for lithium and trims the AGM by up to about 2%. Example: 80 usable Ah ÷ 46 Ah a night = 1.7 nights.

If you use the maker's DC cord or converter instead of an inverter, you skip the inverter's losses and idle draw, so you'll do better than this table.

Whatever battery you use, don't make it the one that starts your truck. ResMed's DC converter page specifically warns not to drain the vehicle's battery. A separate deep-cycle battery or a power station keeps you from waking up to a truck that won't start.

DC cord or AC outlet?

CPAPs like the AirSense 10 run on DC inside. Its power brick puts out 24 V DC. Plugging into an AC outlet means the station or inverter turns DC into AC, then the brick turns it back into DC, and you lose power both ways. CPAP.com says running from a 12 V outlet with a DC adapter is more efficient.

• ResMed: the DC/DC converter for the AirSense 10 runs from a 12 V or 24 V source and works with or without the humidifier and heated tube.
• Philips: DreamStation machines have their own DC cord, which CPAP.com says also powers the heated humidifier and tube.
• Other machines: use only the DC cord or converter your machine's maker sells or lists. A cheap universal adapter can be the wrong voltage or polarity.

Adding solar for longer trips

A panel that puts back each day what the CPAP used each night lets a smaller station last as long as the trip. Our calculators plan on getting about 75% of a panel's rating into the battery. With 5 sun hours:

• 30 W, no humidifier: 282 Wh ÷ (5 × 0.75) = 75 W. Round up to a 100 W panel.
• 53 W, with humidifier: 499 Wh ÷ (5 × 0.75) = 133 W. Round up to a 150 W panel.

Cloudy days and shade cut that a lot, so keep some reserve in the station. Our solar and power station guide covers aiming and shade, and our solar panels page has portable panels.

Tips that stretch your battery

• Turn off the humidifier and heated tube if you can sleep comfortably without them. ResMed's user guide says to turn off the humidifier to get the most from an external battery.
• Use a hose cover. CPAP.com suggests one to cut condensation in the tube without using any power.
• Use DC, not an inverter, for the reasons above.
• Keep the station or battery off the cold ground and inside the tent or camper if you can. Batteries give less in the cold.
• Charge everything full before you leave, and test the whole setup at home for one night before the trip.
• Bring a backup plan. A dedicated CPAP battery, a second small station or a way to recharge during the day.

Questions people ask

How long will a power station run a CPAP?

Divide the station's watt-hours by your nightly use. With our planning figures, a 1,000 Wh station gives about 3.5 nights without a humidifier (1,000 ÷ 282) and about 2 nights with one (1,000 ÷ 499). With the humidifier off and ResMed's measured 7 W, it would be much longer.

Will a 300 Wh power station run a CPAP all night?

Usually, without the humidifier. A 30 W machine uses about 282 Wh in 8 hours by our math, so a 300 Wh station just makes it. With a heated humidifier at 53 W, it runs about 5 hours, so go to 500 Wh or bigger.

Can I run my CPAP off my car battery?

You can with the maker's DC cord or converter, but ResMed warns to be careful not to drain the vehicle's battery. A starting battery isn't built for deep discharges, and running it down overnight can leave you stranded. Use a power station or a separate deep-cycle battery.

Should I use the humidifier when camping on battery?

If you can sleep without it, turning it off makes the biggest difference. ResMed's own test showed the humidifier and heated tube taking the AirSense 10 from about 7 W to about 34 W. Check with your sleep doctor if you're not sure.

Are dedicated CPAP batteries worth it?

They're small and made to plug right in. CPAP.com lists Philips' DreamStation Go battery at 62 Wh and about 13 hours on average, without the humidifier. A power station costs more but also charges phones and runs lights and a cooler.

Can I charge the power station from my truck while I drive?

Yes, most stations charge from a 12 V outlet, but slowly. Jackery lists about 16 hours to recharge its 550 Wh Explorer from a car outlet. Solar or a wall outlet at the campground is much faster.

Do I need a pure sine wave inverter?

Check your CPAP's manual first. Pure sine wave AC is the closest match to wall power, and many power stations, like the Jackery Explorer 1000 v2, list it on the spec sheet. If you're buying a separate inverter, pick a pure sine wave model and size it well above your machine's peak watts.