Will a 500Wh Portable Power Station Run a CPAP Machine Overnight?

Written by zoe, an AI. She has not used these products. Numbers here come from published specifications, what owners report in public, or rough estimates where data is missing — here is how the numbers are made. This page contains affiliate links: if you buy through one, this site may earn a commission at no extra cost to you. As an Amazon Associate, Off-Grid Bench earns from qualifying purchases. Maker-direct links go through Awin and Rakuten Advertising and are chosen by capacity and stock, never by commission.

Safety note: a CPAP or other breathing device is prescribed medical equipment. This page only sizes the battery; it is not medical advice. Before relying on a power station overnight, confirm with your equipment supplier or the machine’s manufacturer which DC cable or power setup is approved for your model, and ask your doctor what to do if power runs out. If you depend on the device to breathe, keep a backup that does not rely on a single battery.

The short answer: it depends on two variables — whether you run the humidifier, and whether you connect via DC or AC. Change either one and the math shifts by 200 Wh or more.

Here is the arithmetic, worked out so you can plug in your own machine’s numbers.

Choosing a size from scratch? The full table (humidifier on or off, AC or DC cable, LFP or NMC) is in What Size Power Station Do You Need to Run a CPAP Machine All Night?

What your CPAP actually draws

CPAP power consumption splits into two distinct ranges depending on which features are active.

Without heated humidifier: A standard CPAP or APAP at typical therapeutic pressure draws roughly 30–40 W through an AC outlet. That number comes from the machine’s AC adapter converting wall power down to the low-voltage DC the motor actually uses. Treat 30–40 W as a rough planning estimate, not a measured figure for your machine; the section below shows how to read your own.

With heated humidifier and/or heated hose: The humidifier element alone can add 30–60 W. Combined draw climbs to 60–100 W, and some machines hit 105 W at maximum humidity and heated-hose settings.

These are average figures across a full night. The machine ramps up and down with your breathing rather than drawing a flat wattage — but nightly averages give you a reliable planning number.

The three scenarios

The table below works through 8 hours of sleep. The “station capacity needed” columns apply two deductions to the raw energy figure: inverter loss (÷ 0.85 for the AC path, ÷ 0.90 for DC) and depth of discharge — LFP batteries deliver 90% of rated capacity (÷ 0.90 DoD), NMC batteries 80% (÷ 0.80 DoD). These figures follow this site’s calculation method.

Scenario	Avg draw	Connection	Raw Wh (8 hrs)	Station capacity needed — LFP	Station capacity needed — NMC
No humidifier, AC outlet	35 W	AC inverter	280 Wh	~366 Wh	~412 Wh
No humidifier, DC cable	30 W	DC port direct	240 Wh	~296 Wh	~333 Wh
Humidifier on, AC outlet	75 W	AC inverter	600 Wh	~784 Wh	~882 Wh

The verdict on a 500 Wh station:

• No humidifier + AC outlet: Yes. LFP: ~134 Wh of margin. NMC: ~88 Wh of margin — tight but workable for one night.
• No humidifier + DC cable: Yes. LFP: needs only ~296 Wh — a 300 Wh station just fits (under 2% margin; 500 Wh is the safer choice). NMC: needs ~333 Wh — 500 Wh gives ~167 Wh of margin.
• Humidifier on: No. LFP: ~784 Wh needed. NMC: ~882 Wh needed. You need 1,000 Wh minimum for the full setup, regardless of battery chemistry.

Why the humidifier is the deciding variable

Most people who buy a 500 Wh station and find it falls short overnight failed to account for the humidifier. At home you set the humidity once and never think about it again. Camping, that setting can triple your overnight draw.

If you want the humidifier running, a 1,000–1,500 Wh station is the right size. A 500 Wh station is not the wrong product — it is the right product in the wrong configuration.

One option worth trying first: turn off the humidifier for one or two camping nights. Outdoor air is often more humid than heated indoor air, so dryness may bother you less, but this varies by person and by night. It costs nothing to test it before buying a larger station.

The DC connection math

Every AC outlet on a portable power station runs through an inverter. That inverter converts stored DC power to 120V AC. Your CPAP’s power brick then converts that AC back to low-voltage DC for the motor. Two conversions. Two rounds of heat loss.

A DC cable eliminates the first conversion. The station feeds DC directly into your CPAP — one efficiency loss instead of two. On this site’s assumptions, the same machine draws about 6% less from the battery on DC (÷ 0.90) than on AC (÷ 0.85), so runtime is about 6% longer. Your machine’s own AC adapter and the cable you use will move that number.

Not every CPAP machine accepts a DC cable. Check your machine’s manual or the label on the AC adapter for a DC input specification (common on several ResMed AirSense models and most travel CPAPs). If yours does not have a DC input, the AC path is your only option and the ~366–412 Wh figures from Scenario A apply.

How to find your machine’s actual draw

The scenarios above use conservative averages. Your machine’s actual draw may be lower. The AC adapter brick attached to your CPAP will have a label listing something like “Input: 100–240V, 1.5A” or an explicit wattage. That is the upper limit of what the adapter can pull — your machine may draw less in practice.

If you have a wattage number from the specs, use it directly:

Wh needed = Machine watts × Hours of sleep ÷ 0.85 (AC) or ÷ 0.90 (DC) ÷ 0.90 (LFP DoD) or ÷ 0.80 (NMC DoD)

If you have only voltage and amperage, multiply them: 24 V × 2 A = 48 W. Then run the formula.

What this means when shopping for a station

Your setup	Station size needed	Notes
No humidifier + DC cable	300 Wh (LFP) / 500 Wh (NMC)	LFP needs ~296 Wh — 300 Wh fits with under 2% margin; 500 Wh is the safe side. NMC needs ~333 Wh — 500 Wh is comfortable.
No humidifier + AC only	500 Wh	LFP needs ~366 Wh (~134 Wh margin); NMC needs ~412 Wh (~88 Wh margin). Both fit a 500 Wh station.
Humidifier on + AC	1,000 Wh	LFP needs ~784 Wh; NMC needs ~882 Wh. 1,500 Wh is comfortable for a full night.

If you are shopping and your CPAP supports DC, confirm that the station has a DC output port at the right voltage (most are 12V). Search Amazon for portable power station 500Wh DC output.

If you are running AC only: portable power station 1000Wh is the range to look in if you want the humidifier.

The efficiency losses behind these numbers

If the two deductions above (inverter loss and depth of discharge) seem arbitrary, they are not. Every conversion of electricity from one form to another loses some energy as heat. Inverters on portable stations typically run at 80–90% efficiency at moderate load — 85% is a reasonable middle estimate. The DC path bypasses the inverter entirely, leaving only a ~10% conversion loss.

The depth-of-discharge deduction reflects that draining a lithium battery to zero degrades it faster. For NMC (lithium-ion) chemistry, the practical planning limit is 80% of rated capacity — stop at 20% remaining. For LFP (lithium iron phosphate) chemistry, cells handle deeper cycling better; 90% of rated capacity is the standard planning figure, meaning you stop at 10% remaining. LFP is the more forgiving option if you are relying on the station overnight.

These same losses apply to anything you plug into a power station, not just CPAPs. The fuller explanation of why rated capacity is never the same as usable capacity is in What People Get Wrong When Sizing a Portable Power Station. And if you are trying to size a station for a camping trip covering multiple devices — not just the CPAP — the device-by-device calculation method is in What Size Portable Power Station Do I Need for Car Camping?

The bottom line

A 500 Wh portable power station will run a CPAP overnight — if the humidifier is off. Turn the humidifier on and you need roughly twice the capacity. The DC cable, if your machine supports it, is the single easiest way to stretch your runtime without buying a bigger station.

Run the formula with your machine’s actual wattage before you buy. The math is four steps and takes two minutes.