Almost any modern inverter generator can power a CPAP machine, because the machine itself draws less than most camping fridges. What matters is pure sine wave output, safe overnight positioning, and enough fuel to last until morning.
Sleep apnoea affects roughly one in four Australian men over 30, and for anyone on CPAP therapy, “can I still go free camping?” is the question that decides whether the van leaves the driveway. Away from powered sites, your machine needs a reliable 240V supply for seven to eight hours every night, without fail.
The good news: a CPAP machine is one of the smallest loads you will ever put on a generator. A typical machine draws 30W to 60W on its own, which is a fraction of what even the most compact Gentrax inverter generator produces. The sizing question is really about everything else you want to run, and the practical questions are about safety, noise, fuel and camp etiquette.
Here is what you need to know about powering CPAP therapy off-grid, and six steps to set it up properly at a free camp.
» MORE: Inverter generator buying guide: sizing by appliance
What Is a CPAP Machine and Why Does It Need Reliable Power?
A CPAP (continuous positive airway pressure) machine is a medical device that treats obstructive sleep apnoea, a condition where the airway repeatedly collapses during sleep, interrupting breathing dozens of times an hour. The machine draws in room air, pressurises it with a small motorised blower, and delivers it through a hose and mask, holding the airway open all night. Common models in Australia include the ResMed AirSense series and Philips DreamStation, most paired with a heated humidifier that warms and moistens the airflow for comfort.
Because therapy only works while the machine is running, power is not optional. An interrupted night means returning apnoea events, fragmented sleep, and next-day fatigue, which matters doubly when tomorrow involves towing a van on unfamiliar roads. Untreated apnoea is also a recognised driver fatigue risk. That is why CPAP users planning to camp beyond powered sites need a power source they can trust from lights out to sunrise, every single night of the trip.
Can a Generator Run a CPAP Machine?
Yes, provided it is an inverter generator with pure sine wave output. CPAP machines contain sensitive pressure sensors, motors, and electronics that expect the same clean power a hospital wall socket delivers. Every generator in the Gentrax range produces pure sine wave 240V at 50Hz, so even the smallest unit runs a CPAP with a large safety margin.
The one thing not to do is run the machine from the generator’s 12V DC outlet. The Gentrax manuals are explicit that the DC output is for 12V battery charging only. Plug your CPAP into the AC socket using its own power supply, or charge a battery by day and run the machine from that battery at night.
How Much Power Does a CPAP Machine Actually Use?
Power draw depends far more on the comfort features than the machine itself. Check the label on your machine’s power brick for the exact figure, then budget for these three scenarios:
- Machine only (30W to 60W): the blower on a typical auto-adjusting machine sips power. At this load, any Gentrax generator is barely above idle with the economy switch on.
- With a heated humidifier (70W to 100W): the humidifier’s heating plate is the biggest single draw. Many campers switch it off or fit a heat and moisture exchanger for trips, halving consumption overnight.
- With a heated hose and humidifier (up to about 150W): the worst case for most machines, and still under 15% of the rated output of even a 1.2kW class generator, such as the Gentrax GT1200.
In other words, the CPAP never decides your generator size. Your fridge, kettle, induction cooktop, or caravan air conditioner does. Work out your biggest simultaneous load first, then confirm the CPAP rides along for free.
Why Pure Sine Wave Output Is Non-Negotiable
Cheap conventional generators and modified sine wave inverters produce a choppy, stepped waveform. Motors run hotter on it, electronics buzz, and manufacturers of medical devices generally void support for damage it causes. A CPAP subjected to dirty power can behave unpredictably: pressure fluctuations, error states, or a controller failure mid-trip, none of which you want to discover at 2 am, three hours from town.
Inverter generators solve this by generating raw power, converting it to DC and rebuilding it digitally into a smooth sine wave. The result is power cleaner than many suburban grids, stable enough for laptops, TVs, drone chargers, and medical devices alike. It is the single most important specification on the box for CPAP users, ahead of wattage, weight and even noise.
How to Run Your CPAP at a Free Camp: 6 Steps
1. Size the Generator for the Whole Camp, Not the CPAP
For a solo swag or tent setup where the CPAP is the main event, an 800W to 1.2kW class generator weighing under 10kg is ample. Add a 240V camping fridge and device charging, and a 2.0kW model gives comfortable headroom. Caravanners running a full site, including a small air conditioner by day, should look at the GT3500 or the GTX4200 Pro, which idles right down to CPAP loads at night.
2. Position It for Carbon Monoxide Safety
This is the step that matters more than all the others combined. Generator exhaust contains carbon monoxide, which is odourless and can be fatal in enclosed spaces. The Gentrax manuals require open-air operation only: never inside a tent, annexe, caravan, or vehicle, never against a canvas or plastic structure, and at least one metre clear of anything on all sides. Place the generator downwind of your sleeping area with the exhaust facing away, and run a quality outdoor-rated extension lead into the tent or van instead of shortening the distance.
3. Protect It from Weather Without Enclosing It
The manuals also prohibit running the generator in rain. If weather threatens, use a purpose-built open-sided generator cover or position it under a hard awning with generous airflow, never wrapped in a tarp. A wet lead or socket is an electrocution risk; keep connections off the ground.
4. Turn the Economy Switch On and Let It Whisper
A CPAP is exactly the steady, light load the economy control switch was designed for. With it on, the engine slows to match demand, cutting both fuel use and noise. Gentrax units already run at 58dB to 62dB at rated load, roughly conversation level from a few metres; at CPAP-only load on eco mode they fade into background bush noise. Leave eco mode off only when starting motor-driven appliances like fridges or pumps, which need a surge of current.
5. Fuel It for the Whole Night Before You Sleep
Never refuel a running or hot generator, so top up before bed. At 50% load, the 1.2kW and 2.0kW models run six to eight hours on their 3.6L tanks; at a 30W to 100W CPAP load with eco mode on, a full tank comfortably outlasts a night’s sleep. The GT3500’s 5.7L tank and the GTX4200 Pro’s 8.8L tank remove the question entirely. Use fresh 91 RON unleaded, and open the fuel cap air vent before starting.
6. Respect Quiet Hours and Know Where Generators Are Welcome
Most Australian national parks prohibit generators outright, and many free camps and showgrounds post quiet hours, typically 8 pm to 8 am or stricter. Check WikiCamps notes or signage before committing to a site. Where overnight running is not permitted, the hybrid setup in the next section keeps your therapy going silently.
Here’s what one of our customers said about Gentrax generators:
“These units are superb! After a very short time, about 2 months, I purchased a second unit to take full advantage of the parallel capability. Wow! These units are easy to start, and they sync very quickly to become a single generator roughly twice the size. Both units (together) provide all the power necessary as a back-up to our off-grid solar system. I was so impressed; I built a small device to automatically start and stop for both units triggered directly from the dry contact of the Growatt SPF 5000 and an ESP8266 I can trigger the remotes of both units to start and stop both generators, automatically when the Growatt considers the batteries are getting low. This is simple and safe, as there is no connection to any 240v power anywhere. The device monitors the generator using a hall effect sensor, so it knows when power is on, and off. These generators work for the first time every time. Say goodbye to solar anxiety.”
Generator vs Portable Power Station: Which Is Better for CPAP?
For overnight CPAP specifically, a lithium portable power station has real advantages: it is silent, legal everywhere including national parks, and safe inside the tent next to your bed. A machine drawing 40W with the humidifier off will run all night on a 500Wh unit with margin to spare.
The generator’s advantage is endurance and everything else. Batteries deplete; a generator refuels in two minutes and also runs the fridge, charges the tools, and boils the kettle. The setup our long-term free campers converge on is the hybrid: a portable power station beside the bed running the CPAP silently overnight, recharged each day in an hour or two from the generator while it is already running the camp. You get silent nights, generator curfew compliance, and unlimited trip length.
What Outbax Customers Running CPAP Setups Should Know Before Buying
- Pure sine wave across the range: every Gentrax inverter generator, from the GT800 Pro to the GTX6600, outputs pure sine wave 240V suitable for sensitive electronics.
- Break the engine in first: a new generator needs about 25 hours under 75% of rated load before heavy duty. A CPAP is the ideal break-in load; see our guide to the first 25 hours of generator ownership before your first big trip.
- Bring a backup plan: CPAP is medical equipment. Carry the machine’s 12V lead or a charged power bank rated for it, and know your machine’s behaviour if power drops mid-cycle. Confirm power specifications with your CPAP supplier before travelling.
Here’s what one of our customers said:
“Ran it a few times and used it to run our cement mixer down the paddock when no electricity ran a couple incubators when we had power issues and charged a battery in the caravan, so far happy. Runs quiet will mainly be used in caravan to boost batteries in over cast days”
Set Up Your Free Camping Power Kit
CPAP therapy should never be the reason a trip stays on the calendar instead of the road. A pure sine wave Gentrax inverter generator, positioned safely and paired with a battery for silent nights, powers your therapy indefinitely, anywhere. Browse the range from 800W to 6.6kW, or reach out to our team and tell us your machine and camp setup; we will match the right unit before you buy.
