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RV Generator Sizing Calculator

Determine the right wattage generator for your RV. Accounts for AC startup surge, microwave, fridge, and other simultaneous loads.

Inputs

Tick each appliance you want to run at the same time. Set quantity if you have more than one.

Surge wattage

Motor-driven appliances (AC, fridges, washers) draw 2-3x their running wattage for the first second when starting. Your generator must handle the surge or it will trip.

Running watts vs surge watts: don't confuse them

Generators have two wattage ratings. Running watts (also called rated watts) is what the generator can produce continuously. Surge watts (also called peak or starting watts) is what it can handle for a few seconds during motor startup.

If you only look at running watts, you'll buy a generator that constantly trips when the AC or fridge starts. The right way is to:

  1. Add up running watts for everything you run simultaneously.
  2. Find the single appliance with the largest extra startup load (surge minus run).
  3. Add that one surge to your continuous total.

Most appliances don't all start at exactly the same instant, so you only need to budget for the worst-case single startup on top of your running load. The calculator does this for you.

Common RV generator sizes

OutputTypical useExamples
2000W inverterSmall fridge, lights, electronics, charging. Will not run AC.Honda EU2200i, Champion 2000
3000-3500W inverterMost 13.5K BTU AC units, plus modest other loadsHonda EU3000iS, Champion 3500
4000W+ inverter15K AC + microwave + fridge simultaneouslyHonda EU7000iS, Predator 4500
Onan 4.0 RV-QGOnboard generator, runs on RV propane or gasClass A and C motorhome standard

Inverter generator vs conventional

For RV use, inverter generators are nearly always the right choice. They produce clean sine-wave power safe for sensitive electronics, run quieter (~50-60dB vs 75-85dB), and use less fuel by varying engine speed with load. The price premium is real but the campground neighbors will appreciate it.

Frequently Asked Questions

Can a 2000W generator run an RV air conditioner?
Generally no. A 13.5K BTU AC needs about 1500 running watts but surges to 3000-3500W on startup. A 2000W generator usually can't handle the surge. With a soft-start kit (such as MicroAir EasyStart or SoftStartRV) you can sometimes drop the surge to under 2000W and make it work, but check the AC manufacturer's specs and your generator's surge rating.
Should I get a propane or gasoline generator?
Propane (or dual-fuel) generators are popular for RVs because they share fuel with your existing propane system, store cleanly long-term, and produce fewer emissions. The tradeoff is about 10% less power output on propane vs gasoline for the same generator. Onboard motorhome generators almost always run on propane.
How long can I run a generator continuously?
Most modern inverter generators are designed for continuous duty as long as fuel and oil are good. The bigger limit is local rules — many campgrounds and BLM areas restrict generator hours (typically 8am-10pm), and noise ordinances apply. Check with your campground host.
Do I need a transfer switch?
Only if you want to run your RV's full electrical system (including outlets and AC) off the generator without manually moving plugs. RVs with onboard generators have an automatic transfer switch built in. For portable generators, plugging directly into the shore power inlet works for most users; an aftermarket auto-transfer switch makes it easier.

Related Calculators

Battery Bank SizerRight-size your house batteries.Solar Panel SizerHow many watts of solar you need.Propane EstimatorDays per tank for your usage.

Want to understand the why behind these numbers? Read Solar vs. Generator — when a generator is the smarter choice.

About our math & sources

Every default and formula in this calculator is grounded in published manufacturer specs, industry standards, or peer-reviewed measurement. Where we make assumptions, we tell you what they are so you can adjust.

  • Appliance running watts. Typical RV appliance ratings from Dometic, Furrion, GE, and Whirlpool spec sheets. AC unit figures match Coleman-Mach, Dometic Penguin II, and Atwood Air Command standard ratings.
  • Surge wattage. Compressor-driven appliances (AC, fridge, washer) typically surge 2–3× running watts at startup. Soft-start kits (MicroAir, SoftStartRV) can reduce this by 50–70%.
  • Recommended sizing tiers. Aligned with the inverter generator product tiers from Honda (EU2200i, EU3000iS, EU7000iS), Champion, Predator, and Westinghouse — the dominant brands in the RV market.
Disclaimer. This calculator provides estimates only. Real-world results depend on equipment efficiency, environmental conditions, and installation quality. Always verify against your equipment's spec sheets and consult a licensed installer for safety-critical decisions.