CPAP Power Outage: How Long Will a Backup Battery Actually Run Your Machine?
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Reading time: about 7 minutes. Written by the biomedical engineering team at OHM Medical IT.
If you rely on CPAP or BiPAP, a power outage isn't an inconvenience — it's a night of untreated sleep apnoea, or lying awake waiting for the power to come back. Storm season, grid load-shedding, a tripped safety switch at 2 am, a week in a caravan: sooner or later everyone on therapy asks the same question. How long will a backup battery actually run my machine?
The honest answer is "it depends on three settings", and most product listings won't tell you which ones. This guide does.
The three things that decide runtime
1. Heated humidifier — the big one
A modern CPAP blower on its own is remarkably frugal: at typical pressures a ResMed AirSense 10 or 11, or a Philips DreamStation, draws in the region of 5–10 W. Switch on the heated humidifier and the draw rises to roughly 20–35 W depending on the humidity setting and room temperature. That's a three- to five-fold difference from one setting.
2. Heated tube (ClimateLine / heated tubing)
Heated tubing adds a further load on top of the humidifier, and it's the setting most people forget. Humidifier plus heated tube on a cold night can push some machines toward 40 W or more.
3. Pressure and mode
Higher pressures, BiPAP and mask leak all increase blower work. The effect is real but much smaller than the humidifier — think 10–30 %, not 300 %.
The runtime maths
Runtime is simply usable battery energy (Wh) ÷ your machine's draw (W). "Usable" matters: a UPS or inverter loses some energy converting battery power to what the machine needs, so budget roughly 80–85 % of the nameplate capacity.
Take the Zopec Explore 5500, a 160 Wh medical-style UPS battery designed specifically for CPAP and BiPAP. Assuming around 130 Wh usable:
| Your settings | Typical draw | Estimated runtime (Explore 5500, 160 Wh) |
|---|---|---|
| CPAP only, humidifier off | ~6–10 W | Roughly 13–20 hours (two nights for many users) |
| CPAP + heated humidifier | ~20–35 W | Roughly 4–6 hours |
| CPAP + humidifier + heated tube | ~30–45 W | Roughly 3–4 hours |
| BiPAP, humidifier off | ~8–15 W | Roughly 9–15 hours |
Estimates based on typical published and bench-measured power draw for current ResMed and Philips machines at common pressures. Your machine, pressure, mask leak and room temperature will move these numbers. Two Explore 5500 units can be linked for double the capacity.
The practical takeaway: on battery, turn the humidifier and heated tube off (or use the humidifier on a low passive setting if your machine allows it). One night of slightly drier air is a much better outcome than three hours of therapy followed by five hours without.
"Backup battery" vs. "UPS" — why it matters at 2 am
Many CPAP batteries sold online are simply portable power banks with a DC lead. They work — but you have to notice the power has gone off, get up, find the battery and plug it in. Half-asleep, with a mask on, most people don't.
A CPAP UPS sits permanently between the wall and your machine. When mains fails, it switches to battery automatically and the machine never stops. The Explore 5500 uses an online double-conversion design, which means your machine is running from clean, conditioned power the whole time and there's no switchover gap at all. It's silent (no fan), it lives on the bedside table, and it charges itself back up when the power returns.
Choosing a CPAP battery in Australia: a short checklist
- Automatic switchover. If you'd have to wake up to use it, it's not backup — it's a spare.
- Capacity in Wh, not mAh. Wh is what runtime is calculated from. 160 Wh is a sensible minimum for a full night with the humidifier off; less than 100 Wh is a travel/nap battery.
- Compatibility with your exact machine. AirSense 10, AirSense 11, AirMini, DreamStation 1 and 2, Löwenstein, F&P SleepStyle all have different connectors and voltages. Check before you buy, or ask us — it takes two minutes.
- Airline-legal for travel. Batteries under 160 Wh are generally accepted as carry-on by Australian airlines (always confirm with your carrier). The Explore 5500 sits right at that limit; the smaller Explore Mini (99.5 Wh) is the no-questions-asked travel option.
- Recharge options. Wall, 12 V vehicle and solar charging matter if you're caravanning or off-grid.
- Safety and support. Lithium batteries on a bedside table should come from a supplier who can answer the phone. Ours is a biomedical engineering company; that's our day job.
Camping, caravans and grey-nomad travel
The same maths applies, but you'll want to recharge daily. A 160 Wh unit on humidifier-off settings will typically do two nights, and can be topped up from the vehicle's 12 V socket while driving (45 W vehicle charger, under about six hours to full) or from a portable solar panel. If you run the humidifier every night in the van, plan on linking two units or charging every day.
What we recommend
- Home outage protection, one machine: Zopec Explore 5500 left permanently connected as a UPS.
- Frequent flyer / short trips: Zopec Explore Mini.
- Home ventilation, BiPAP with humidification, or oxygen concentrators: talk to us — these usually need a medical-grade UPS such as the Zopec UPS 90, and sizing matters.
Not sure what your machine draws or which battery fits it? Send us the model and your usual settings via the contact page or call 03 9115 7464 and one of our engineers will give you a straight answer on runtime before you spend anything.
OHM Medical IT is the Medical IT division of SASS Biomedical Engineering Services Pty Ltd (trading as OHM Healthcare), an Australian-owned biomedical engineering company based in Tullamarine, Victoria. This article is general information about backup power and is not medical advice; follow your sleep physician's and device manufacturer's instructions. Runtime figures are estimates and will vary with your equipment and settings.
