What Size Generator Do I Need for a Van or RV?
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 case | Load estimate | Minimum generator |
|---|---|---|
| Battery charging only (30A charger) | ~500–600W | 1,000–1,500W |
| Battery charging + laptop | ~600W | 1,500W |
| Battery charging (55A charger) | ~900W | 1,500W |
| Battery charging + induction cooking | ~2,000W | 2,500W+ |
| Running 5,000 BTU portable AC | 500W run, 1,500W surge | 2,000W (check surge) |
| Running 13,500 BTU rooftop RV AC | 1,500W run, 3,000W+ surge | 3,500W+ |
| Running 13,500 BTU AC + charging | 2,000W+ | 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).
Recommended generator sizes
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.