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What Size Generator Do I Need for a Van or RV?

How to size a generator for a van or RV — wattage requirements for battery charging, running AC, and common appliances, with US product recommendations.

Updated June 20, 20263 min readPractical, transparent guidance
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Generator sizing for a van or RV comes down to what you actually need to run from it. Most van lifers only need a generator for battery charging and occasional appliance use — 2,000W covers this well. If you need to run an air conditioner, the calculation changes.

For generator brand recommendations: best generator for RV & van use.

Step 1: List your loads

Battery charging only: Your converter/charger is the main load. A 30A charger at 14.4V output draws about 432W from the battery side — at 90% efficiency, it pulls about 480W from the generator. A 55A charger pulls about 880W. Add a laptop (60W) or lights (30W) and you're still well under 2,000W.

Running AC loads simultaneously: If you want to power appliances directly from the generator (not through the battery/inverter), add their wattages. Induction cooktop: 1,500W. Hair dryer: 1,500W. Running these alongside battery charging can exceed 2,000W.

Sizing by use case

Use caseLoad estimateMinimum generator
Battery charging only (30A charger)~500–600W1,000–1,500W
Battery charging + laptop~600W1,500W
Battery charging (55A charger)~900W1,500W
Battery charging + induction cooking~2,000W2,500W+
Running 5,000 BTU portable AC500W run, 1,500W surge2,000W (check surge)
Running 13,500 BTU rooftop RV AC1,500W run, 3,000W+ surge3,500W+
Running 13,500 BTU AC + charging2,000W+4,000W+

Continuous vs peak wattage

Every generator has two ratings:

  • Continuous (running) watts: What it can sustain indefinitely
  • Peak (surge) watts: What it can provide for a few seconds during startup

Always size by continuous watts for your running loads, but check that peak watts exceeds the startup surge of any motor-driven appliances (AC units, compressors).

2,000W inverter generator (Honda EU2200i, WEN 56200i): Right for the vast majority of van builds — battery charging, laptop, lights, small appliances.

3,000W inverter generator (Champion 3500W Dual Fuel, Yamaha EF3000iS): Needed if you want to charge batteries AND run a portable AC unit simultaneously.

4,000W+ generator: Only necessary for large rooftop RV AC units (13,500 BTU+) plus other loads.

Don't forget runtime

A generator that outputs 2,000W but burns a gallon of fuel per hour may not be practical for extended use. Check fuel efficiency at your expected load level. Honda and Yamaha inverter generators are notably more fuel-efficient than conventional generators — at 25% load (500W), a Honda EU2200i runs for 8+ hours on a single tank.

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