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.

Understanding RV power plugs

RVs use a few standard shore-power connections:

• 30-amp service uses a three-prong TT-30 plug at 120 volts. The maximum is about 3,600 watts (30 amps × 120 volts).
• 50-amp service uses a four-prong 14-50 plug with two 120-volt legs, each up to 50 amps. In total that's up to about 12,000 watts.
• Smaller trailers may use a standard 15/20-amp household plug.

Your generator doesn't have to supply the full rating of the RV's service. It only needs to cover what you'll actually run at once. But the connection has to match: a generator with a TT-30R outlet can plug directly into a 30-amp RV cord. A 50-amp RV can run from a 30-amp source through an adapter, but you'll be limited to about 3,600 watts, often on a single leg.

A load list for a typical travel trailer

Appliance	Running watts	Starting watts
13,500 Btu rooftop AC	about 1,300 to 1,800	about 2,500 to 3,500 (less with a soft-start kit)
Converter/charger (charging batteries)	300 to 800	none
Microwave	1,000 to 1,500	none
Refrigerator on electric mode	300 to 400	none
Water heater on electric mode	about 1,400	none
Coffee maker	600 to 1,200	none

These are typical figures. Check your RV's appliance labels and owner's manual. The rooftop air conditioner's starting surge is usually the deciding factor. A soft-start kit installed on the AC compressor can cut the surge significantly, sometimes letting a 2,200 to 3,000-watt inverter generator start an AC that would otherwise need a bigger unit.

Managing loads in the campground

Even a correctly sized generator can trip if everything runs at once. Common habits:

• Turn off the electric water heater element and use propane mode while the AC is running.
• Don't run the microwave and AC together on a small generator.
• Set the converter to charge during low-load periods.
• Use the RV's energy management system if it has one. Many 50-amp coaches can shed loads automatically.

Noise and campground etiquette

Campgrounds and public lands often set generator hours and noise limits. National Park Service campgrounds, for example, typically allow generator use only during posted hours, and some areas prohibit generators entirely. Inverter generators are much quieter at light loads, which is one reason they're popular with RVers. Position the exhaust away from neighboring sites and your own windows, and never run a generator in an enclosed space or under an awning where exhaust can collect.

Carbon monoxide in RVs

RVs are small, enclosed spaces, and CO can build up fast. Make sure the RV's CO alarm works. Test it before every trip, and replace it on the manufacturer's schedule. Don't sleep with a generator running if exhaust could drift into the coach, for example when snow, a wall, or another vehicle is blocking airflow. Ready.gov's guidance to keep generators at least 20 feet from windows and doors applies at campsites too.

Fuel planning for boondocking

When you're camping without hookups, fuel and battery storage go together. Running the generator a couple of hours in the morning and evening to recharge batteries, rather than continuously, saves fuel and keeps the peace. Solar panels can reduce generator hours further. Estimate daily generator hours, multiply by your generator's gallons per hour at the expected load, and carry enough for the trip plus a margin.