What size power station do I need to run a CPAP all night?

A CPAP is one of the easiest things to run on a power station. It uses little power, and it makes no startup surge. The one setting that changes everything is the heated humidifier.

First, a medical note. We're not your doctor or your equipment supplier. If you rely on your CPAP, have a backup plan for outages, and ask your doctor and your supplier how to run it on battery. Ask them too before you turn the humidifier off. Ready.gov advises anyone who uses power-dependent medical devices to talk to their medical provider about an outage plan.

How many watts does a CPAP use?

Champion's wattage chart lists:

CPAP setup	Typical watts
Humidifier off (no heat)	30 to 60 W
With heated humidifier	60 to 120 W

Your machine could be higher or lower, depending on its model and pressure. The best number is your own. Plug the CPAP into the power station one night while the grid is still on, and read the watts on the station's display. Many stations show watts out.

How many Wh does a CPAP need for one night?

Wh per night = CPAP watts × hours of sleep

For an 8-hour night:

CPAP setup	Energy at the machine	Plan for on AC (÷ 0.85)
Humidifier off	240 to 480 Wh	about 280 to 565 Wh
Humidifier on	480 to 960 Wh	about 565 to 1,130 Wh

The second column is what the CPAP itself uses. The last column adds about 15% for the energy lost when the station turns battery power into 120 V AC. We use 85% efficiency. Try 80% to 90% in the calculator.

Worked example

Your CPAP draws 50 W with the humidifier off. You sleep 8 hours.

• CPAP energy: 50 W × 8 h = 400 Wh
• Plus AC losses: 400 ÷ 0.85 = about 470 Wh

A 500 Wh station just covers one night. That leaves almost no margin, so a bigger battery is safer.

Now turn the heated humidifier on, and say it draws 100 W:

• 100 W × 8 h = 800 Wh
• 800 ÷ 0.85 = about 940 Wh

Now you need about 1,000 Wh for the same night. The heat roughly doubles what you need.

What size power station for a CPAP?

You want	Humidifier off	Humidifier on
One night	about 500 Wh	about 1,000 Wh
Two nights	about 1,000 Wh	about 2,000 Wh
Three nights	about 1,500 Wh	about 3,000 Wh

These assume 8 hours on AC at the middle of Champion's ranges. Round up. Outages rarely end on schedule, and a station also uses a little power for its own screen and fans.

How long will a 300, 500 or 1,000 Wh station run a CPAP?

Hours = station Wh × 0.85 ÷ CPAP watts

Here it is for a CPAP drawing 45 W with the humidifier off, or 90 W with it on. Those are the middles of Champion's ranges.

Power station	Humidifier off (45 W)	Humidifier on (90 W)
300 Wh	about 5.5 hours	about 3 hours
500 Wh	about 9 hours	about 4.5 hours
1,000 Wh	about 19 hours	about 9 hours
2,000 Wh	about 38 hours	about 19 hours

A small 300 Wh station may not get you through a full night, even with the heat off. These numbers are on AC. Running from DC can stretch them.

DC adapter vs AC outlet

You can plug your CPAP's normal power brick into the station's AC outlet. That's simple, and it works.

You can also run many CPAPs from 12 V DC using the maker's DC adapter. ResMed, for example, sells a DC/DC converter for one of its CPAP lines that works from a 12 V or 24 V source, like a car or boat battery. A power station's 12 V car-style port can be that source.

Why bother? Going DC skips the station's AC inverter. Less energy is wasted, so the same battery lasts longer. It also means you can leave the station's AC side off overnight.

Before you rely on DC:

• Use the adapter your CPAP maker lists for your model.
• Check that the station's 12 V port can supply the adapter's rating. ResMed lists its converter's output as 90 W.
• Test it at home, on a normal night, before an outage.

Humidifier on or off?

Turning off the heat is the single biggest way to stretch a battery. It can roughly halve the energy you need. Some people find dry air uncomfortable, though. Ask your doctor or supplier whether it's OK for you, and check your CPAP manual for how to turn the heat off.

Tips to make it through the night

• Charge the station fully before a storm. In storage, top it up every few months; Generac, for one, says to recharge its stations every three months.
• Test a full night at home while the power is on. Note the battery percentage in the morning.
• Keep a second plan. That might be a second battery, a car charger, a neighbor with power, or a place to go.

Can I charge the station from a generator?

Yes. Run the generator outdoors by day, charge the station, then sleep with the quiet battery beside your bed. Never bring the generator inside, not even to a garage or porch. See our power station vs generator comparison for how people combine them.

Before you use any generator, read our generator carbon monoxide safety guide.