What Size Generator Do I Need to Run a 3-Ton Central Air Conditioner?
Tonnage sets the watts. Use the chart row that matches the outdoor unit.
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Running and starting watts
| Load | Running watts | Starting watts | Source |
|---|---|---|---|
| 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 |
Honda's wattage 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. Not listed means that source does not give a separate starting figure.
How to size it
Add the running watts of every load that will be on together, then add the single highest starting surge (Generac; Honda). Generac notes that starting watts are often 2–3 times running watts, and that standby units should get a dealer survey.
The 2-ton row on the same chart is 2,000–2,500 running watts and 3,500–4,500 starting watts. The manual's 6,250 W starting rating covers that 4,500 W start. Parallel EU2200i output of up to 4,400 W does not. The condenser is hardwired, so use a transfer switch or interlock installed by an electrician. See the transfer switch sizing guide.
Generac recommends a dealer survey before you buy a standby unit for this kind of motor.
Check a full load list on the generator size calculator.
Run the generator outdoors only, 20 ft from the house (CPSC).
FAQ
Can the Champion 5,000 W generator run a 3-ton AC?
Its published ratings do. The manual lists 5,000 W running and 6,250 W starting. Champion's 3-ton row tops out at 3,500 W running and 6,000 W starting. That is the air conditioner alone.
Will two EU2200i generators in parallel run a 3-ton AC?
Parallel output is up to 4,400 W. The 3-ton start is 5,000–6,000 W, which is higher.
What does a 2-ton system need?
Champion lists 2,000–2,500 running watts and 3,500–4,500 starting watts. The 6,250 W starting rating covers that row.
Where is the 4-ton figure?
On the 4-ton page. Champion lists that row at 4,000–5,000 running watts and 6,500–8,000 starting watts, which is above the 6,250 W starting rating.
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