About 19.3 hours. A 500 Wh power station has roughly 425 Wh usable, and a CPAP machine averages about 22 W. Depending on the model the range is about 9.7 to 60.7 hours.
- Runtime
- 19.3 hEstimate at average draw
- Usable energy
- 425 Wh85% of 500 Wh
- Average draw
- 22 W22 W while running
- Surge
- NoneNo motor start
The math
| Usable capacity | 500 Wh × 0.85 = 425 Wh |
|---|---|
| Average draw | 22 W running × 1 duty = 22 W |
| Runtime | 425 ÷ 22 = 19.3 h |
Things to check
- Turning off the heated humidifier and tube cuts the draw sharply; a DC adapter avoids inverter losses. Ask your equipment supplier what your model supports.
Other battery sizes
Questions people ask
How long will a 500 Wh power station run a CPAP machine?
About 19.3 hours (about 19.3 hours). A 500 Wh power station has roughly 425 Wh usable, and a CPAP machine averages about 22 W. Depending on the model the range is about 9.7 to 60.7 hours.
How many watts does a CPAP machine use?
A CPAP uses about 7-10 watts with the humidifier off and about 22 watts with the heated humidifier on, rising to 34-44 W with a heated tube (ResMed test data). Power supplies are rated 65-90 W, but real draw is far lower.
How do you calculate power station runtime?
Hours ≈ capacity in Wh × 0.85 ÷ average watts. The 0.85 allows for inverter and battery losses.