Generator size by appliance / CPAP
What size generator runs a CPAP machine
CPAP machine (ResMed AirSense 11): 73.2 W running with no starting surge in the source table, so a generator needs 73.2 W of running capacity for it. The smallest of the six portables this site covers that can do it is the Honda EU2200i (1,800 W running, 2,200 W max).
ResMed's user guide gives the AirSense 11 a peak power consumption of 73.2 W and a typical consumption of 56.1 W, so the calculator uses the peak figure. The guide does not list the humidifier's draw separately, and other models differ.
Any of the six portables here can run a CPAP machine by itself; the question is usually what else runs at the same time, and whether the machine is near enough to the generator to be safe from carbon monoxide.
Ask the equipment supplier whether your device may run from a generator and whether a battery backup is available for it.
The figures and where they come from
| Device | Source | Running W | Additional starting W | Starting need alone |
|---|---|---|---|---|
| CPAP machine (ResMed AirSense 11) | ResMed AirSense 11 guide | 73.2 | — | 73.2 |
Highlighted rows are the figures the calculator uses. Every table here prints additional starting watts: the surge on top of running watts. Peak power consumption; typical is 56.1 W.
Which portables can run it
| Generator | Running / peak W | Alone | With fridge, 6 LED bulbs, 2 chargers |
|---|---|---|---|
| Honda EU2200i | 1,800 / 2,200 | Yes | No |
| Honda EU3000iS | 2,800 / 3,000 | Yes | No |
| Westinghouse iGen5000 | 3,900 / 5,000 | Yes | Yes |
| Honda EU7000iS | 5,500 / 7,000 | Yes | Yes |
| Champion 201040 | 7,500 / 9,375 | Yes | Yes |
| Westinghouse WGen9500DF | 9,500 / 12,500 | Yes | Yes |
A generator fits when its running rating covers every running watt and its peak (or "max") rating covers the running total plus the single biggest starting surge. Adding the basics — a refrigerator (700 W running, 2,200 W to start), six 15 W LED bulbs and two phone chargers — raises the running load to 903.2 W and the starting need to 3,103.2 W, because the refrigerator's surge is now the biggest one. The smallest portable here that covers that is the Westinghouse iGen5000.
On a standby generator
A home standby unit is rated in kilowatts and has no overload capacity: Generac's rating definition says "No overload capability is available for this rating." Using Generac's own formula — sum of running watts plus the highest single starting burst — the CPAP with the basics needs 3.1 kW. The smallest Guardian model that covers it on natural gas is the 10 kW, rated 9 kW on natural gas and 10 kW on propane, which leaves 5.9 kW of starting room for everything else. Whole-home lists are on the standby generator pages.
Before running anything, read the carbon monoxide distance rules and how a transfer switch keeps power off the utility lines. Other appliances: refrigerator · sump pump · well pump · furnace · window AC · central air · heat pump · space heater · water heater · washing machine · garage door opener · oxygen concentrator.