How long will a power station run a CPAP?
Most CPAP machines draw 30 to 60 W without the humidifier. The heated humidifier is the big variable: with it on, the draw often reaches 90 W or more. The tables below assume 40 W and 90 W, 8-hour nights, and 85% efficiency on AC.
Without the humidifier (40 W)
| Station | Continuous runtime | Nights (8 h each) |
|---|---|---|
| 300 Wh | 6 h 23 min | 0.8 nights |
| 500 Wh | 10 h 38 min | 1.3 nights |
| 1,000 Wh | 21 h 15 min | 2.7 nights |
| 1,500 Wh | 31 h 53 min | 4.0 nights |
| 2,000 Wh | 42 h 30 min | 5.3 nights |
With a heated humidifier (90 W)
| Station | Continuous runtime | Nights (8 h each) |
|---|---|---|
| 300 Wh | 2 h 50 min | 0.4 nights |
| 500 Wh | 4 h 43 min | 0.6 nights |
| 1,000 Wh | 9 h 27 min | 1.2 nights |
| 1,500 Wh | 14 h 10 min | 1.8 nights |
| 2,000 Wh | 18 h 53 min | 2.4 nights |
Getting more nights from the same station
- Turn the humidifier off, or use it unheated. That usually doubles the nights.
- Use the DC outlet with your manufacturer’s DC power cord if one is made for your machine. That skips the conversion to AC, which typically saves 10 to 15%.
- Check your machine’s actual draw. The power supply label shows the maximum, not the typical draw. A plug-in power meter over one night gives the real figure.
Talk to your equipment supplier before relying on battery power for therapy. These are planning estimates, not medical advice.