What size generator for an RV or camper?

RV generator sizing is simpler than a house because there are fewer loads and a hard ceiling: the RV’s own electrical service.

Know your service

• 30-amp RV (TT-30 plug, three prongs): one 120-volt circuit, 30 amps. Maximum about 3,600 watts.
• 50-amp RV (14-50 plug, four prongs): two 120-volt legs of 50 amps each. Maximum about 12,000 watts.

There is no point feeding a 30-amp RV from a generator much larger than 3,600 running watts, because the RV’s main breaker will trip first. A 50-amp rig can use far more, but most owners run only part of that on a generator.

The air conditioner sets the size

Champion lists a 13,500-BTU RV air conditioner at 1,500 to 2,000 running watts and 2,800 to 3,500 starting watts. With the RV refrigerator on electric (150 to 600 running) and the converter charging batteries, a 30-amp rig running one AC typically needs:

• about 2,500 to 3,000 running watts, and
• a starting rating that covers the AC surge on top of everything else.

That is why roughly 3,000-watt inverter generators are popular with 30-amp trailers. With a soft-start device on the AC, a smaller generator or a pair of 2,000-watt-class inverters in parallel may start the AC reliably.

One generator or two in parallel?

Many inverter generators can be linked with a parallel kit, combining output. Two smaller units:

• are lighter to lift in and out of a truck,
• give you a backup if one fails,
• let you run just one on mild days to save fuel.

One larger unit is simpler, may cost less overall, and needs only one set of maintenance. Both approaches work.

50-amp coaches

A 50-amp coach with two air conditioners typically needs a larger generator with 120/240-volt output and a 50-amp outlet, or a built-in onboard generator. Running both ACs, a residential refrigerator, and an electric water heater can exceed what most portables can supply; many owners run one AC at a time on a portable.

Campground rules

Many public campgrounds limit generator hours and noise. National Park Service campgrounds, for example, publish specific generator hours for each campground. Check the rules where you are going; a quieter inverter generator makes this easier.

Try the numbers

Use the RV amp calculator to add up your loads and see how close you are to your service limit, then check the running and starting watts against any generator you are considering.