Generator size by appliance / garage door opener
What size generator runs a garage door opener
Garage door opener, 1/2 hp: 875 W running plus 2,350 W more for a few seconds as it starts, so a generator needs at least 3,225 W of starting capacity to run it on its own. The smallest of the six portables this site covers that can do it is the Westinghouse iGen5000 (3,900 W running, 5,000 W peak).
A garage door opener runs for a few seconds at a time, but Generac lists a 1/2 hp opener with a 2,350 W starting surge on top of 875 W running, more than a refrigerator's surge.
Most openers have a manual release, so during an outage many people open the door by hand rather than size a generator around it.
Never run the generator inside the garage, even with the door open: the CPSC and FEMA both say so in plain terms.
The figures and where they come from
| Device | Source | Running W | Additional starting W | Starting need alone |
|---|---|---|---|---|
| Garage door opener, 1/2 hp | Generac GP brochure (2023) | 875 | 2,350 | 3,225 |
Highlighted rows are the figures the calculator uses. Every table here prints additional starting watts: the surge on top of running watts.
Which portables can run it
| Generator | Running / peak W | Alone | With fridge, 6 LED bulbs, 2 chargers |
|---|---|---|---|
| Honda EU2200i | 1,800 / 2,200 | No | No |
| Honda EU3000iS | 2,800 / 3,000 | No | 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 1,705 W and the starting need to 4,055 W. 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 garage door opener with the basics needs 4.1 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 4.9 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 · CPAP · oxygen concentrator.