How many watts does a CPAP machine use
While a CPAP machine is running, it uses 30 to 60 W, and there is no starting surge. The smallest portable that can run it comes in at 2,000 W.
Watts for running and starting
| Load | Running | Starting |
|---|---|---|
| CPAP, no heated humidifier | 30 to 60 W | no surge |
Source: the Champion wattage chart, 04-17-26. Your own CPAP machine's nameplate shows its exact wattage, or its amperage. To get watts, multiply amps by 120 V, and use 240 V only when the load runs on a two-pole breaker, for instance a well pump.
Smallest generator able to start it
A generator has to carry 60 W without going past 80% of its rating. Among common portable sizes, the smallest is 2,000 W, and it handles both with room to spare. Every other load shares that generator and adds its running watts.
CPAP, no heated humidifier, plus other loads
| CPAP, no heated humidifier plus | Running | Peak at a start | Smallest portable |
|---|---|---|---|
| lights, TV and the router | 630 W | 630 W | 2,000 W |
| a freezer and lights | 710 W | 1,210 W | 2,000 W |
| a 1/2 hp sump pump and lights | 1,260 W | 2,360 W | 2,000 W |
| a microwave | 1,260 W | 1,260 W | 2,000 W |
| a 1 hp well pump | 2,060 W | 4,060 W | 3,500 W |
| a window AC, 10,000 BTU | 1,260 W | 2,460 W | 2,000 W |
Running watts add together, and only the largest motor start sits on top. Starting output for a portable comes in about 25% higher than its running rating. The appliance wattage chart lists every load.