How Many Watts Does a CPAP Use? The Numbers, and the Arithmetic

A CPAP is a small load right up until the humidifier comes on. The blower draws 10–15 W; the heated humidifier draws 50–75 W more. That six-fold difference is the single most important number in sizing a battery for overnight therapy, and it’s the one most sizing advice skips.

Everything below is worked out rather than asserted, so you can substitute your own machine’s figures.

How many watts does a CPAP use?#

10–15 watts running on DC with humidification off, and 60–90 watts with a heated humidifier on.

Broken into its parts:

Component	Typical draw	What it does
Blower motor	10–15 W	Delivers your prescribed pressure
Heated humidifier	50–75 W	Warms the water chamber
Heated tube	10–20 W	Prevents condensation in the hose
Total, no humidification	10–15 W
Total, humidifier on	60–90 W
Total, humidifier + heated tube	70–110 W

These are typical ranges across current machines, not your machine’s numbers. Pressure setting, room temperature and humidifier level all move them — a humidifier working in a cold room runs its element harder than one in a warm one, which is why winter camping costs more energy than the same trip in July.

Why isn’t the number on the label the right one?#

Because the label states what the power supply can deliver at maximum, not what the machine averages overnight.

Most CPAP power bricks are marked 65 W or 90 W. Size a battery from that and you’ll conclude you need 520–720 Wh for a night with no humidifier — five times the real requirement. The rated figure exists so the supply can cover the humidifier’s startup heating and peak pressure simultaneously, which is a condition your machine spends almost none of the night in.

Use average draw for capacity, and rated draw only to check the inverter can start the machine. Those are two different questions and they need two different numbers.

How many watt-hours does a CPAP use per night?#

Roughly 100 Wh without humidification and 500–700 Wh with it, for an eight-hour night.

The arithmetic is watts × hours:

No humidifier: 12.5 W × 8 h = 100 Wh

Humidifier on: 75 W × 8 h = 600 Wh

Humidifier + heated tube: 90 W × 8 h = 720 Wh

Using mid-range figures. Substitute your own machine’s draw and the same multiplication applies.

What size battery does that need?#

More than the nightly figure, because the inverter loses about 15% of what the battery holds.

A power station stores DC and your wall outlet needs AC, so the inverter converts — and conversion is never free. Across this site we size at 85% inverter efficiency, the same figure the sizing calculator uses, so a guide and the calculator never disagree.

That means capacity needed = watt-hours ÷ 0.85:

Scenario	Wh per night	Battery capacity needed	Class
1 night, no humidifier	100 Wh	118 Wh	Any small unit
3 nights, no humidifier	300 Wh	353 Wh	500 Wh class
1 night, humidifier	600 Wh	706 Wh	1 kWh class
2 nights, humidifier	1,200 Wh	1,412 Wh	2 kWh class
3 nights, humidifier	1,800 Wh	2,118 Wh	2 kWh class
1 night, humidifier + heated tube	720 Wh	847 Wh	1 kWh class

The humidifier moves you up two whole capacity classes. That is the practical consequence of the six-fold draw difference, and it’s worth about $700 in purchase price.

Note that these figures apply identically whether the product is sold as a portable power station or as a solar generator — the second is the same battery with panels in the box. Panels change how you refill it between nights, not how much it holds, so size the battery from the table above first and treat solar as a separate question.

Does running on DC instead of AC save power?#

Yes — about 15%, because it skips two conversions.

Powering the machine from a power station’s AC outlet means the battery’s DC is inverted to AC, then your machine’s power brick rectifies it back to DC. Both steps lose energy as heat. A DC cable made for your specific model plugs straight into the battery’s 12 V output and skips both.

On AC: 100 Wh of therapy needs 118 Wh from the battery

On DC: 100 Wh of therapy needs roughly 100 Wh from the battery

On a humidified night the same 15% is about 90 Wh — most of an extra hour of therapy from the same battery. Most manufacturers do not support the heated humidifier over DC, which is worth knowing before you buy the cable: the DC route usually means accepting no humidification, and the energy saving comes mostly from that rather than from the conversion.

Does a higher pressure setting use more power?#

Yes, but far less than you’d expect — the humidifier still dominates.

The blower is a small motor, and pushing more air costs more energy. Across the usual therapy range the difference is roughly a few watts:

Pressure	Typical blower draw	Wh per 8 h
6 cmH₂O	~8–10 W	64–80 Wh
10 cmH₂O	~10–13 W	80–104 Wh
14 cmH₂O	~13–17 W	104–136 Wh
20 cmH₂O	~17–22 W	136–176 Wh

So going from a low pressure to a high one might cost you 70 Wh across a night — meaningful if you’re running a 288 Wh travel unit for a third night, irrelevant next to the humidifier’s 500–700 Wh.

The same logic applies to auto-adjusting machines, which spend most of the night below their maximum. Sizing from the maximum pressure is conservative rather than wrong; if you’re close to a capacity boundary it’s worth measuring your own average rather than assuming the top of the range.

A mask leak is the hidden variable. A leaking mask makes the blower work harder all night to hold pressure, which raises draw and shortens runtime. If your battery runs out sooner than this page predicts, that’s the first thing worth checking — and it’s worth checking for therapy reasons regardless.

What inverter size do you need?#

300 W is enough for the blower alone; 600 W or more if the humidifier runs from AC.

This is the question the rated label figure is actually for. Your machine’s supply is marked 65–90 W, and an inverter has to cover that peak, not the average — plus headroom for the humidifier element switching on.

Any power station in the small class has at least a 300 W inverter, so machine startup is never the constraint. Capacity is.

There’s a second inverter question — pure sine wave versus modified sine wave — which matters more for a CPAP than the wattage does. We cover it separately in pure sine wave inverters for CPAP.

What should you check on your own machine?#

Its label, and then its actual draw if you can measure it.

The label is on the underside or the back of the unit and on the power brick. It gives you input voltage and rated wattage, which tells you the inverter requirement.

For average draw, the honest answer is that the ranges on this page are typical rather than yours. A plug-in energy meter between the wall and the machine, left running for a night, gives you your own number — and it is the one worth sizing from.

One thing not to do: don’t turn the humidifier down or off to make a battery last longer without discussing it with whoever manages your therapy. Humidification is prescribed for a reason, and a battery is the cheaper thing to change.

How does this compare to other overnight loads?#

A CPAP without humidification is one of the smallest genuine loads you can put on a power station. With humidification it’s one of the larger ones.

Load	Watts	Wh per 8 hours
CPAP, no humidifier	10–15 W	~100 Wh
LED lighting	5–10 W	40–80 Wh
12 V fridge (duty-cycled)	45 W running	~108 Wh
CPAP with humidifier	60–90 W	480–720 Wh
CPAP + heated tube	70–110 W	560–880 Wh
Starlink Standard	50–75 W	400–600 Wh

The gap between the first and fourth rows is the whole story. A humidified CPAP costs more energy overnight than a 12 V fridge, which surprises most people and explains why so many buyers under-size.

Where to go next#

• Best power stations for CPAP — the picks, once you know your number
• Pure sine wave inverters for CPAP — the other inverter question
• Best Jackery for CPAP — if you’ve settled on the brand
• Sizing calculator — run your own loads

This page is spec-driven research, not medical advice. The energy arithmetic is ours; decisions about your therapy settings belong with your clinician.