Generator sizing chart
Published October 6, 2026.
Built by Jeremy Panasuk.
Every row below is copied from a one-appliance page on this site. Those pages cite Honda's wattage guide or Champion's chart. This page does not add a third set of watts.
Quick answer: Honda lists a garage door opener at 720 running watts and 1,420 starting watts. On this site's calculator that is a 2,000 W recommendation. A band such as 100–500 means the chart printed a range. "Not listed" means that source did not print a separate starting figure.
The rows
Honda's guide lists starting watts, then running watts. Champion's chart lists running watts, then starting watts. This table puts every figure in the Running and Starting columns. Each load name links to the page that walks that appliance. Where both sources print a row, both rows are here.
| Load | Running watts | Starting watts | Source |
|---|
| Energy Star fridge / freezer | 132–192 | 1,200 | Honda |
| Fridge | 150–400 | 800–1,200 | Champion |
| Freezer | 100–500 | 500–1,000 | Champion |
| Window AC, 5k BTU | 450–600 | 900–1,200 | Champion |
| Window AC, 10k BTU | 900–1,200 | 1,800–2,400 | Champion |
| Window AC, 10k BTU | 1,500 | 2,200 | Honda |
| Central AC, 2 ton | 2,000–2,500 | 3,500–4,500 | Champion |
| Central AC, 3 ton | 3,000–3,500 | 5,000–6,000 | Champion |
| Central AC, 4 ton | 4,000–5,000 | 6,500–8,000 | Champion |
| Furnace fan, 1/8 hp | 300 | 500 | Honda |
| Furnace fan, 1/6 hp | 500 | 750 | Honda |
| Furnace fan, 1/4 hp | 600 | 1,000 | Honda |
| Furnace fan, 1/3 hp | 700 | 1,400 | Honda |
| Furnace fan, 1/2 hp | 875 | 2,350 | Honda |
| Furnace fan, 1/2 hp | 300–800 | 800–1,600 | Champion |
| Hot water heater (240 V) | 4,500 | 4,500 | Honda |
| Electric water heater | 3,000–4,500 | Not listed | Champion |
| Electric clothes dryer (240 V) | 5,400 | 6,750 | Honda |
| Electric dryer | 4,000–6,000 | Not listed | Champion |
| Automatic washer | 1,200 | 1,200 | Honda |
| Washing machine | 500–1,000 | 1,000–2,300 | Champion |
| Dishwasher, cool dry | 216 | 540 | Honda |
| Dishwasher | 1,200–2,400 | Not listed | Champion |
| Microwave, 650 W cooking | 1,000 | 1,000 | Honda |
| Microwave, 800 W cooking | 1,300 | 1,300 | Honda |
| Microwave, 1,000 W cooking | 1,500 | 1,500 | Honda |
| Microwave | 600–1,200 | Not listed | Champion |
| Range, 8-inch element (240 V) | 2,100 | 2,100 | Honda |
| Range, one burner | 1,200–2,400 | Not listed | Champion |
| Radiant heater | 1,300 | 1,300 | Honda |
| Space heater | 750–1,500 | Not listed | Champion |
| CPAP | 30–60 | Not listed | Champion |
| CPAP, heated | 60–120 | Not listed | Champion |
| Flat TV, 20-inch | 120 | 120 | Honda |
| Flat TV, 46-inch | 190 | 190 | Honda |
| Router | 10–20 | Not listed | Champion |
| Sump pump, 1/3 hp | 800 | 1,300 | Honda |
| Sump pump, 1/2 hp | 1,050 | 2,150 | Honda |
| Sump pump, 1/3 hp | 500–800 | 1,000–1,600 | Champion |
| Sump pump, 1/2 hp | 800–1,050 | 1,300–2,150 | Champion |
| Well pump, 1/2 hp | 750–1,000 | 1,500–2,000 | Champion |
| Well pump, 1 hp | 1,000–2,000 | 2,000–4,000 | Champion |
| Garage door opener | 720 | 1,420 | Honda |
| RV AC, 13,500 BTU | 1,800 | 2,800 | Honda |
| RV AC, 13.5k BTU | 1,500–2,000 | 2,800–3,500 | Champion |
| RV AC, 15,000 BTU | 2,000 | 3,300 | Honda |
| RV AC, 15k BTU | 2,000–2,500 | 3,500–4,500 | Champion |
| Air compressor, 1/2 hp | 975 | 1,600 | Honda |
| Air compressor, 1 hp | 1,600 | 4,500 | Honda |
| Air compressor, 1 hp | 1,500 | 4,500 | Champion |
| Air compressor, 2 hp | 2,500 | 7,500 | Champion |
| Air compressor, 3 hp | 3,500 | 10,500 | Champion |
| Table saw, 10-inch | 1,800 | 4,500 | Honda |
| Table saw, 10-inch | 1,800–3,000 | 3,600–6,000 | Champion |
| Pressure washer, 1 hp | 1,200 | 3,600 | Honda |
| Pressure washer, 1,500 psi | 1,200–1,500 | 2,400–3,000 | Champion |
| Pressure washer, 2,500 psi | 2,000–2,500 | 4,000–5,000 | Champion |
| Welder, 120 V | 1,800–2,500 | 3,600–5,000 | Champion |
| Welder, 240 V (comparison) | 3,000–8,000 | 6,000–16,000 | Champion |
The short house table on the home calculator is not this chart. Where those two disagree, use the row on the appliance page, which names Honda or Champion. Nameplate running watts, starting watts, tank size, and run time at a stated load are a different table, on the portable generator watts chart.
Worked example: the garage door opener
The home calculator adds running watts, keeps the single highest starting watts, then adds only the part of that start above that load's own running watts. Headroom defaults to 20%. The recommendation rounds up to the next 500 W.
Honda's garage door opener is 720 running watts and 1,420 starting watts. Extra starting watts = 1,420 − 720 = 700. Peak = 720 + 700 = 1,420. With 20% headroom, 1,420 × 1.20 = 1,704, which rounds up to 2,000 W recommended. A Honda EU2200i is rated 1,800 W with a 2,200 W maximum, which covers the 720 W run and the 1,420 W start. Buying for 720 W running only misses the start. The same walk is on what size generator for a garage door opener.
A combined refrigerator and freezer list, which is more than one row, is on refrigerator and freezer and on the longer fridge and freezer guide.
Run the generator outdoors only, at least 20 feet from the house, never inside, including a garage with the door open (CPSC). Connecting it to a building takes a licensed electrician and a permit where local code requires one.
Compiled with AI assistance from the sources below. Spot an error? Email [email protected].
Sources