If you rely on a CPAP, a power outage is more than an inconvenience. It means a night without therapy. Luckily, a CPAP is one of the easiest devices to back up, and a small, quiet power station can cover several nights.
Step 1: Find out how much power your CPAP really uses
It mostly depends on whether you use the heated humidifier:
| Setup | Typical draw | Energy per 8-hour night |
|---|---|---|
| CPAP only, low pressure | 30–40 W | 240–320 Wh |
| CPAP only, high pressure | 50–60 W | 400–480 Wh |
| CPAP + heated humidifier | 80–100 W | 640–800 Wh |
| CPAP + humidifier + heated tube | 90–110 W | 720–880 Wh |
The number printed on the power brick, say 90 W, is the maximum, not what the machine pulls all night. Real use is usually well below it.
Step 2: Use DC power if you can
Plugging the normal AC brick into a power station wastes energy twice. The battery’s DC power goes through the inverter to become AC, and then the brick turns it back into DC. You lose 10–20% along the way, and the inverter uses a few watts of its own just being on.
The big CPAP makers (ResMed, Philips, Fisher & Paykel) all sell a 12 V or 24 V DC cord. Plugged into the power station’s car port, it can stretch runtime by 20–40%. Switching off the humidifier during an outage roughly doubles it again.
Step 3: Pick a size by the number of nights
Assuming 40 W on DC with no humidifier:
| Power station size | Approx. nights (DC, no humidifier) | With humidifier (AC) |
|---|---|---|
| 250–300 Wh | 1–2 nights | Less than 1 night |
| 500 Wh | 2–3 nights | About 1 night |
| 1,000 Wh | 5–6 nights | About 2 nights |
What to look for
Quiet matters most, because this thing sits next to your bed. Some cooling fans are loud, so look for units that stay silent at low loads; many smaller power stations rarely spin their fans at 40 W.
After that, you want a regulated 12 V car port, which keeps the voltage steady as the battery drains and matters for DC CPAP cords, and LiFePO4 cells, which are safer and last 3,000+ cycles. UPS or pass-through mode is very handy: the unit switches to battery on its own when the power goes out, so you don’t wake up. Under 30 milliseconds of switchover is ideal for a CPAP. And if you travel or camp, a 250–300 Wh unit weighs under 9 lb.
Which size for which situation
- For occasional short outages, travel or camping, a 250–300 Wh LiFePO4 unit with a DC cord is plenty.
- For multi-night outages, or if you use the humidifier, a 1,000 Wh unit covers several nights and can run a fridge as well.
- If you use an oxygen concentrator as well as a CPAP, talk to your doctor and size for both. A home concentrator alone can pull around 300 W. The power station size calculator can help.
Medical note: if missing therapy is a serious risk for you, talk to your doctor and your equipment supplier about a backup plan, and sign up for your utility’s medical-priority program if it has one.