What Size Generator Do I Need to Run a 4-Ton Central Air Conditioner?

This condenser is a whole-house load, and the published start sits above a common portable surge rating.

Quick answer: Champion lists a 4-ton central air conditioner at 4,000–5,000 running watts and 6,500–8,000 starting watts. Covering that row takes a running rating that clears 5,000 W and a starting rating that clears 8,000 W. The Champion manual lists 5,000 W running and 6,250 W starting, so that starting figure is below the 6,500–8,000 W start.

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Running and starting watts

Load	Running watts	Starting watts	Source
Central AC, 4 ton	4,000–5,000	6,500–8,000	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 manual's 5,000 W running figure meets the top of the 4,000–5,000 W running range, and its 6,250 W starting figure does not meet a start of 6,500–8,000 W. Parallel EU2200i output tops out at 4,400 W, which is below both the running and starting figures. 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 for a standby unit.

Check a full load list on the generator size calculator.

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Run the generator outdoors only, 20 ft from the house (CPSC).

FAQ

Will a 6,250 W starting rating run a 4-ton AC?

Not the top of this chart. Champion lists the start at 6,500–8,000 W. The manual lists 6,250 W starting.

What running watts does a 4-ton system list?

Champion lists 4,000–5,000 running watts.

Can two EU2200i units in parallel cover it?

No. Parallel output is up to 4,400 W. The 4-ton running range already reaches 5,000 W, and the start reaches 8,000 W.

Is a 3-ton system the same question?

No. Champion lists 3-ton equipment at 3,000–3,500 running watts and 5,000–6,000 starting watts. Use the 3-ton page for that row.