How this calculator works
How we size your generator
We add up the running watts of everything you tick, then add the largest single starting surge, because appliances rarely all start at once. Running and starting watts come from Honda's generator wattage guide, except the induction cooktop and the battery charger, which are our estimates (check your own appliance's label).
If your A/C has a soft start, we cut its starting surge in half. Soft-start makers claim more (one says up to 75% less startup current), but real results vary, so we stay on the safe side. At altitude, we increase the size you need by about 3.5% for every 1,000 feet, as Honda advises.
Common sizes
Common RV generator sizes
- 2,200-watt inverter: About 1,800 running watts. Quiet and light; runs the fridge, TV, coffee maker, and charging, and sometimes a small A/C with a soft start.
- Two 2,200-watt inverters in parallel: About 3,600 running watts together, enough for a 13,500 BTU A/C plus a few small appliances.
- 3,500 watts and up, or built-in: For a 15,000 BTU A/C, two air conditioners, or running a microwave and A/C together.
- Hookups for comparison: A 30-amp hookup supplies 3,600 watts and a 50-amp hookup up to 12,000 watts.
Generator tips
Tips for using a generator with your RV
- Run it outside, away from windows: Carbon monoxide is deadly. Point the exhaust away from your RV and your neighbors', and keep your CO alarm working.
- Check campground quiet hours: Many campgrounds and national parks limit generator hours.
- Stagger big loads: Don't run the microwave and the hair dryer at the same moment as the A/C starts.
Helpful gear
Gear for running your RV on a generator
- RV A/C soft start: Cuts the A/C's starting surge so a smaller generator can run it.
- Inverter generator: Quiet, fuel-efficient power for campsites.
- Parallel kit and 30-amp adapter: Links two inverter generators and plugs them into your RV.
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Common questions
Frequently asked questions
What size generator do I need to run my RV air conditioner? +
A 13,500 BTU rooftop A/C needs about 1,800 running watts and about 2,800 watts to start, according to Honda's wattage guide. A 15,000 BTU unit needs about 2,000 running and 3,300 starting watts. Add everything else you'll run at the same time.
Can a 2,200-watt generator run an RV air conditioner? +
Often not on its own: a 2,200-watt inverter generator like Honda's EU2200i is rated at 1,800 running watts, and a 13,500 BTU A/C needs about that much just to run, plus a starting surge. A soft start reduces the surge, and two 2,200-watt generators linked in parallel give about 3,600 running watts.
What's the difference between running and starting watts? +
Running watts are what an appliance uses steadily. Starting watts are the brief extra surge some appliances, like an A/C or a fridge, need for a moment when they start. Size your generator for all running watts plus the single biggest surge.
How many watts does a 30-amp RV use? +
A 30-amp RV hookup supplies up to 3,600 watts (120 volts times 30 amps). A 50-amp RV can draw up to 12,000 watts.
Do generators lose power at high altitude? +
Yes. Honda says engine power drops about 3.5% for each 1,000 feet of altitude. At 5,000 feet, a generator gives roughly 17% less power.
How do I calculate the generator wattage I need? +
Add up the running watts of everything you want to use at the same time. Then add the extra starting watts of the single appliance with the biggest startup surge, which in an RV is usually the air conditioner. The total is the starting wattage your generator must handle, and the running total is what it must supply steadily. Our generator wattage calculator does the math for you, and adjusts for altitude and soft-start kits.
Will a 3,500-watt generator run my RV? +
Usually, for an RV with one air conditioner. A generator rated for about 3,500 running watts (around 4,000 starting watts) typically runs one 15,000 BTU A/C plus a few small appliances, and a soft-start kit lowers the A/C's startup surge. Check your own A/C's rating, since some need more. Two air conditioners, or a 50-amp RV running several big appliances at once, usually need a larger or built-in generator. Enter your appliances above to check.