CPAP Runtime on a Power Station: DC vs AC, and How Many Nights You Get

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If you use a CPAP, a power outage is not just an inconvenience. It can mean a bad night or several. A power station can keep the machine running, and the math is easier than for most appliances because a CPAP's draw is fairly steady. The big variables are the heated humidifier, the heated tube, and whether you power the machine from the station's AC outlet or its DC port.

Medical note. WattFortress is not a medical resource. Talk to your doctor or equipment supplier about outage plans, especially if you rely on supplemental oxygen or other powered devices. Some power station makers say not to use their products with medical or life-support equipment; Jackery's Explorer 5000 Plus product page, for example, says Jackery does not recommend its power stations for medical devices. Read your power station's manual and your CPAP's manual, and have a backup plan.

Step 1: Find your CPAP's power figures

Use your machine's user guide, not a forum post. ResMed's AirSense 11 user guide (Americas edition) lists for the 65W power supply unit:

• Typical power consumption: 56.1W (111.5VA)
• Peak power consumption: 73.2W (137.6VA)

ResMed lists these as power-supply figures. Actual draw depends on pressure settings, humidifier level, heated tubing and room temperature. ResMed's figure doesn't state whether the humidifier or heated tube was on, so treat it as a planning number. Without humidification, draw is usually much lower, but measure your own setup before relying on that.

The best number is your own. Plug the CPAP into a plug-in watt meter for a full night and read the total watt-hours in the morning.

Step 2: Energy per night

Using ResMed's typical figure and an 8-hour night:

• 56.1W × 8h = 449Wh at the CPAP's power supply

That 449Wh is what the CPAP's AC adapter pulls from the wall. A power station has to make that AC with its inverter, which loses energy.

Step 3: AC path (CPAP plugged into the station's outlet)

Assumptions we use across WattFortress:

• Inverter efficiency: 85% (we use the low end of a typical 85-90% range)
• Usable depth of discharge: 90% (leaves a reserve)

Battery energy per night = 449Wh ÷ 0.85 = 528Wh

Then add the station's own idle draw. This matters for a small load like a CPAP. BLUETTI lists 30W for the AC500 with AC and DC on; Jackery lists 50W standby for the 5000 Plus. Anker's F3800 Plus page says about 40W with AC on and nothing connected; we did not find a published idle figure for the DELTA Pro 3 or DELTA Pro Ultra X. Using 30W as an example:

• Idle over 8 hours: 30W × 8h = 240Wh
• Total per night: 528 + 240 = 768Wh

That idle draw is almost half the CPAP's own energy. On a small load, the inverter's overhead is the largest single inefficiency.

Step 4: DC path (CPAP on a DC adapter)

ResMed sells an Air11 DC/DC converter for the AirSense 11, listed in the user guide as an accessory. A DC converter lets you run the CPAP from a 12V or 24V DC source, like a power station's car outlet, without turning the inverter on.

Why that helps:

1. You skip the DC-to-AC-to-DC conversion (station inverter, then CPAP adapter).
2. You may be able to leave the station's AC inverter off overnight, which removes most of the idle draw.

How much does it save? That depends on the DC converter's efficiency and the station's DC-output overhead, neither of which we found published. What we can say: the DC path removes the 85% inverter loss and most of the inverter idle draw from the equation, so it will usually run more nights than AC on the same battery.

The 12V outputs on the stations we track (from spec pages):

Check that the converter's plug matches the outlet, and use the cable ResMed specifies.

Step 5: Nights per charge (AC path)

Using 528Wh per night from the battery, plus an example 30W idle draw (240Wh per night):

Example math for the DELTA Pro 3: 4,096Wh × 0.90 = 3,686Wh; 3,686 ÷ (528 + 240) = 4.8 nights.

These are estimates built on ResMed's typical figure, not measured results. If your humidifier runs high in a cold bedroom, expect fewer nights. If you run without humidification, expect more.

In practice most people buying a multi-kWh station are also backing up a fridge, lights and internet. The CPAP is a small slice of that budget. See Refrigerator runtime during an outage to add the fridge.

Smaller stations for CPAP-only backup

If the CPAP is the only thing you need to run, a much smaller station can work. The same math applies: a 1,000Wh station at 90% usable gives 900Wh; at 768Wh per night (AC path with 30W idle) that is about 1.2 nights, while DC with low overhead could be meaningfully more. Check the station's published capacity and DC output specs before buying.

Tips for more nights

1. Turn off the heated tube or lower humidity during outages, if your doctor is fine with it.
2. Use the DC path if your CPAP maker offers a DC converter.
3. Turn off every station output you are not using (USB, AC, DC).
4. Keep the station charged to 100% during storm season.
5. Recharge from solar during the day in a long outage.

FAQ

Can I run a CPAP from a power station's AC outlet? Yes, if the outlet is pure sine wave and the station's continuous rating is well above the CPAP's peak draw (73.2W for the AirSense 11 power supply, per ResMed). All the stations above are rated in the thousands of watts.

Will the station switch over automatically if the power fails at night? Many stations have a UPS or pass-through mode. Manufacturer switchover figures: DELTA Pro 3 10ms; BLUETTI AC500 20ms; Anker F3800 under 20ms; Jackery 5000 Plus under 20ms (backup UPS) or 0ms (online UPS). We did not find ResMed guidance on UPS switchover, so ask your CPAP maker whether its machine tolerates that switchover.

Is it safe to keep a power station in the bedroom? Read the station's manual for placement guidance. LFP batteries are used in all the stations listed, and several makers list low noise levels. Keep vents clear.

Does altitude or pressure setting change runtime? Higher pressure settings generally mean more fan work and higher draw. Measure your setup.

Product links: Check price EcoFlow DELTA Pro 3 · Check price Jackery Explorer 5000 Plus · Check price Anker SOLIX F3800 · Check price BLUETTI AC500 · Check price ResMed Air11 DC/DC Converter