Power Station Runtime for a CPAP

Updated 2026-11-12 · Published by Charland & Co. · Based on published specs; we have not tested the products discussed.

Important: read before you use this guide

This page is general information only. It is not professional, electrical or safety advice, and every figure is an estimate.
Always follow your equipment maker’s manual and your local electrical and building codes.
Hire a licensed electrician for any wiring or any connection to a home, cabin or RV electrical system. Never plug a generator into a wall outlet.
Fuel generators are for outdoor use only. Their exhaust contains carbon monoxide (CO), which can kill within minutes. The U.S. Consumer Product Safety Commission (CPSC) says to keep them at least 20 feet from doors, windows and vents.
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Quick answer: For a USA planning example, a 40 W CPAP load for 8 hours is 40 x 8 = 320 Wh. A 400 Wh station at a 0.80 usable share is 400 x 0.80 = 320 Wh, and 320 / 40 = 8 hours. This is not a medical claim. Follow the CPAP maker manual and a clinician.

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All numbers here are estimates for planning only - not professional, electrical, medical, or safety advice. This page does not tell anyone to use or skip a CPAP, and it is not a medical claim. Follow the CPAP maker manual and a clinician. A licensed electrician should handle wiring, a transfer switch, or a panel in the USA. Fuel generators stay outdoors, never in a house, a garage, or near windows, doors, or vents, because of carbon monoxide. Store fuel in an approved container, away from ignition. A swollen lithium pack is a fire risk: do not use it, and follow the station maker manual for charge and storage. For planning questions about this page, see our contact page. See runtime hours from battery watt-hours and how many watt-hours you need.

Medical devices: the runtimes on this page are estimates only. Real runtime depends on your device's actual power draw (a humidifier or heated hose can raise it a lot), the station's usable capacity, temperature and battery age. Check your device maker's power specifications, and talk to your doctor or medical equipment supplier before you count on any backup power. Never rely on a portable power station as the only power source for life-sustaining equipment such as a CPAP, BiPAP or oxygen concentrator. Keep a backup plan (a second power source, spare batteries approved by the device maker, or a place to go). Tell your electric utility about your medical needs; many have a medical-needs or priority registration. This page is not medical advice.

Fuel-burning generators make carbon monoxide (CO), which you can't see or smell and which can kill in minutes. Run them outdoors only, at least 20 ft (6 m) from any doors, windows and vents, with the exhaust pointed away from the home. Never run one inside a home, garage, basement, shed, tent or RV, even with the door or windows open. Install battery-operated or battery-backup CO alarms on every level of your home and outside sleeping areas, and test them monthly. If a CO alarm sounds, or anyone feels dizzy, sick, confused or weak, get to fresh air right away, then call 911. Battery power stations make no CO and can be used indoors, but don't charge or store them where they get hot or wet, and follow the maker's manual.

What this page plans, and what it does not

This page plans how long a portable power station might run a CPAP load when you use the watts from the machine's nameplate. It is a runtime-planning class, not a therapy page, not a diagnosis page, and not a medical claim. If a clinician has told you that you need a CPAP, take runtime questions to that clinician and to the CPAP maker manual. This site does not decide whether a machine should run during an outage, at camp, or in a car.

A power station is a battery pack with an inverter. Runtime is usable watt-hours divided by the average watts the CPAP actually draws, including any humidifier or heated hose the nameplate or manual includes. The 40 W and 8 hour figures later in this page are planning assumptions, not a typical-patient rating and not a product test.

A fuel generator is a different class. It can make a lot of power, but it emits carbon monoxide. Never run a fuel generator indoors, in a garage, or near windows, doors, or vents. Keep it outdoors and away from the building. If that class is in the plan at all, use an approved fuel container and follow the generator maker manual. House wiring, a transfer switch, or a panel is a job for a licensed electrician. Do not backfeed a panel.

Runtime classes: the criteria table

Shop the class first, not a brand name. The example numbers below are planning assumptions, not product specs, test results, or prices.

Class	Best for	Watch out for	Example planning numbers
Portable power station, CPAP runtime plan	A labelled overnight load from the nameplate	Not a medical claim; humidifier watts can raise the load	40 x 8 = 320 Wh; 400 x 0.80 = 320 Wh usable; 320 / 40 = 8 h
Fuel generator (outdoor only)	A larger load when a station's watts or watt-hours are short	Carbon monoxide; never indoors, in a garage, or near windows	Outdoor placement and an approved fuel container, per the maker manual
General power-station buying	Choosing a station class before a CPAP-specific plan	A buying guide is not a runtime page	See the live power station buying guide

Start with the nameplate. Write the running watts, any listed starting or peak watts, and whether a humidifier or heated hose is on. Then write the hours you need to cover, as a planning window, not as a prescription. Then write a usable share of the station's rated watt-hours. This pack uses 0.80 as a planning share for inverter and reserve loss; it is not a product rating. Recheck with the station maker manual and with efficiency and losses.

Cold weather can cut usable capacity. See cold weather battery capacity if the plan includes a cold night. Lithium fire safety still applies in any season: do not use a swollen pack, and follow the maker rules for charge, storage, and transport.

Runtime math, written stepwise

Energy is watts times hours. For a USA planning example, a 40 W CPAP load running 8 hours is 40 x 8 = 320 Wh. That 40 W figure is a planning assumption. Use the number on your nameplate, including accessories the manual says will be on.

Usable energy is rated watt-hours times a planning share. A 400 Wh station at 0.80 is 400 x 0.80 = 320 Wh usable. Then 320 / 40 = 8 hours. If the nameplate is 50 W, do not keep the 8 hour figure. Recalculate: 320 / 50 = 6.4 hours at the same usable watt-hours. If you need 8 hours at 50 W, 50 x 8 = 400 Wh, and at a 0.80 share the rated pack would need to satisfy 400 / 0.80 = 500 Wh. Write each step. Do not collapse three factors into one equation.

The same method is on the live runtime hours and battery watt-hours pages. This page only applies it to a CPAP nameplate load. Watts still have to fit the station's continuous and surge ratings. A station that has the watt-hours but not the running watts will shut down or will not start the load.

How to pick a station for a CPAP runtime plan

Write four facts from the CPAP maker manual and the station maker manual, not from a forum: running watts with the accessories you actually use; any peak or starting watts; the hours you want to plan; and the station's continuous watts, surge watts, and rated watt-hours. Then apply a usable share and recompute. Confirm inverter wave type and outlet type against the CPAP maker manual. This page does not claim that any wave type is medically better; it only says to follow the two manuals.

If the watts or the hours do not fit, options are a larger station class, a lower accessory load if the CPAP maker allows it, or a different power class such as an outdoor fuel generator. A generator still needs outdoor placement, distance from windows, an approved fuel container, and a licensed electrician if it will tie to a building. A clinician is still the right person for any question about using the machine itself.

Charge and storage follow the station maker manual. Park the pack where it will not overheat, and do not use a swollen, damaged, or recalled battery. That is lithium fire safety, not a medical instruction. If you also want a general size comparison, use the live 500 / 1,000 / 2,000 Wh comparison and then come back to this nameplate math.

Worked planning example

A USA camping or outage plan uses a 40 W nameplate CPAP load for 8 hours. Energy: 40 x 8 = 320 Wh. A 400 Wh station at a 0.80 usable share is 400 x 0.80 = 320 Wh, and 320 / 40 = 8 hours. If a humidifier raises the nameplate to 50 W, 50 x 8 = 400 Wh, and 320 / 50 = 6.4 hours on that same 320 Wh usable pack, which is short of 8 hours. The planning answer is then a larger usable pack, or a shorter window, not a guess.

If someone proposes a 200 Wh pack at the same 0.80 share, 200 x 0.80 = 160 Wh, and 160 / 40 = 4 hours. That is only half of an 8 hour window. Label every figure as a planning assumption and recheck the nameplate.

Common mistakes

The first mistake is reading this page as medical advice. It is not a medical claim. Follow the CPAP maker manual and a clinician. The second is using a brochure watt number instead of the nameplate, or leaving out humidifier watts. The third is using rated watt-hours as if they were usable, with no share for inverter loss. The fourth is ignoring the station's continuous-watt limit.

The fifth is bringing a fuel generator indoors or into a garage, or setting it near a window, because of carbon monoxide. Keep fuel in an approved container. The sixth is using a swollen lithium pack. Do not use it. Follow the station maker manual. The seventh is DIY house wiring or backfeeding a panel; that is a job for a licensed electrician.

Who this is not for

This page is not for a clinician visit, a life-support plan, or a therapy claim. It is not a fuel-generator install guide and not a transfer-switch diagram. If you are choosing a station in general, start with the buying guide. If you are adding other house loads, use weekend home-backup sizing. For watt and watt-hour definitions, use watt-hours vs watts.

FAQ

Can a power station run a CPAP?

Sometimes, for a limited time. Runtime here is an estimate only. It depends on your CPAP's actual draw (humidifier and heated hose raise it), the station's real usable capacity, temperature and battery age. Check your CPAP maker's power specs and talk to your doctor or equipment supplier. Never rely on a power station as the only power for a CPAP or any life-sustaining equipment.

Is this medical advice?

No. This page is runtime planning only. Follow the CPAP maker manual and a clinician.

What if my CPAP nameplate is not 40 W?

Do not keep the 8 hour figure. Recalculate watts times hours, then divide usable watt-hours by those watts. The method is the same as runtime hours from battery watt-hours.

Can I use a fuel generator indoors if it is just for a CPAP?

No. Never run a fuel generator indoors, in a garage, or near windows, doors, or vents, because of carbon monoxide. Use an approved fuel container, and keep the unit outdoors.

What if the battery pack looks swollen?

Do not use it. That is a lithium fire risk. Follow the station maker manual, and do not try to repair the pack yourself.

Who should handle house wiring?

A licensed electrician. Do not backfeed a panel or install a transfer switch yourself.

Next step

Read the CPAP nameplate and both maker manuals. Recompute watts times hours and the usable share. Talk to a clinician about any question of using the machine. Keep fuel generators outdoors, away from windows, with fuel in an approved container. Do not use a swollen pack. For a planning question on this page, see our contact page.