What Size Generator Do You Need for a Class A, B or C RV?
By the Generator Size Calculator Team · Updated · 6 min read
Quick answer: Cummins gives these ranges: Class B van with one air conditioner, 2,000 to 3,600 watts; Class C, one air conditioner, 2,800 to 4,000; Class A, two air conditioners, 5,500 to 8,000; fifth wheel, two air conditioners, 5,500 to 7,000; and Class A, three air conditioners, 10,000 to 12,500. The air conditioner count does most of the deciding.
Generator ranges by RV type
| RV type | Air conditioners | Generator range (Cummins) |
|---|---|---|
| Class B van | One | 2,000 to 3,600 W |
| Class C RV | One | 2,800 to 4,000 W |
| Fifth wheel | Two | 5,500 to 7,000 W |
| Class A RV | Two (15,000 BTU) | 5,500 to 8,000 W |
| Class A RV | Three (15,000 BTU) | 10,000 to 12,500 W |
Cummins adds that these ranges can change with your specific equipment. They are starting points, not rules.
Why the air conditioner decides
A 13,500 to 15,000 BTU air conditioner uses 1,200 to 2,400 running watts and up to three times that at start-up, which makes it the biggest load in most rigs by far. Fridge, microwave, TV and lights together are often under 3,000 watts. So the number of air conditioners sets the size, and a rig with none, or one that you rarely run, can use a much smaller generator. Read what size generator runs an RV air conditioner.
Picking within a range
- Low end if you manage loads, run one thing at a time, or use a soft starter on the air conditioner.
- High end if you want to run the air conditioner and the microwave together, or expect hot weather and high altitude.
- Mind the shore power limit. A 30 amp rig can only draw 3,600 watts. See 30 amp and 50 amp RV generators.
Add the loads you run on a hot day.
Tips before you buy
- Check weight and size. A big generator is heavy to carry and store.
- Consider inverters. They are quieter and burn less fuel at light load. See inverter vs conventional generators.
- Check campground rules. Many limit generator size, hours or noise.
- Plan fuel. See the fuel tank size calculator.
Run the generator outdoors, well away from the RV's doors, windows and vents. Carbon monoxide can build up inside a camper even with a window open. See how far a generator should be from a building.
Frequently asked questions
What size generator for a Class C RV?
Cummins suggests 2,800 to 4,000 watts for a Class C with one air conditioner.
What size generator for a Class B van?
Cummins suggests 2,000 to 3,600 watts for a Class B with one air conditioner.
What size generator for a Class A with two air conditioners?
Cummins suggests 5,500 to 8,000 watts for two 15,000 BTU units.
What size generator for a Class A with three air conditioners?
Cummins suggests 10,000 to 12,500 watts.
What size generator for a fifth wheel?
Cummins suggests 5,500 to 7,000 watts for a fifth wheel with two air conditioners.
Related calculators
Sources: Cummins, What size generator do I need to power an RV? (generator ranges by RV type); Cummins, RV generator electricity basics (air conditioner running and start-up watts).