RV generator and battery size calculator
Pick what you run in your RV or camper van (rooftop AC, fridge, water pump, microwave) to see which generator, inverter and lithium battery bank you need, with days of boondocking.
Updated
1. Pick your appliances
Choose how many of each appliance you want to run and how many hours a day they run. Wattages are typical values: check the label on your own appliances.
Microwave (1,000 W)
1,000 W running · 1,000 W starting
0 / 10Coffee maker
1,000 W running · 1,000 W starting
0 / 1012 V RV fridge (compressor)
60 W running · 120 W starting
0 / 10RV rooftop AC (13,500 BTU)
1,300 W running · 2,800 W starting
0 / 2RV furnace blower
50 W running · 100 W starting
0 / 10RV water pump
60 W running · 120 W starting
0 / 10LED lights (whole house)
100 W running · 100 W starting
0 / 10TV (55")
150 W running · 150 W starting
0 / 10Wi-Fi router + modem
20 W running · 20 W starting
0 / 10Laptop
60 W running · 60 W starting
0 / 10CPAP machine (no humidifier)
60 W running · 60 W starting
0 / 2Mini fridge
100 W running · 300 W starting
0 / 2Air fryer
1,500 W running · 1,500 W starting
0 / 10Toaster oven
1,200 W running · 1,200 W starting
0 / 10Portable AC (8,000 BTU)
900 W running · 2,700 W starting
0 / 2Box fan
100 W running · 100 W starting
0 / 3Electric blanket
100 W running · 100 W starting
0 / 2Hair dryer
1,500 W running · 1,500 W starting
0 / 10PS5
200 W running · 200 W starting
0 / 10
2. Your result
We add up the running watts, then add the single largest starting surge (motors never all start at the same second).
Recommended generator size
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Add at least one appliance to see your result.
- Running watts
- 0 W
- Starting peak
- 0 W
- Energy used per day
- 0 Wh
Power source
Frequently asked questions
How many watts is 30 amp and 50 amp RV service?
A 30 A RV service is a single 120 V leg, so 30 × 120 = 3,600 W. A 50 A service has two 120 V legs, so 2 × 50 × 120 = 12,000 W. Your generator only needs to cover what you actually run at the same time, not the full pedestal rating.
Can I run a generator indoors or in the garage?
No, never. The CDC reports more than 400 deaths from accidental carbon monoxide poisoning in the US each year, and the CPSC counts about 85 deaths a year from portable gasoline generators alone. The CPSC says to run a generator outside only, at least 20 feet from the house, with the exhaust pointed away from doors, windows and vents.
Why are starting watts higher than running watts?
Anything with a motor or compressor (fridge, AC, pumps) draws 2 to 3 times its running watts for a second or two when it starts. The calculator adds the single largest surge, because in practice motors don't all kick on at the same moment.
Why add a 20% safety margin?
A generator or inverter running at 100% all the time runs hot, wears faster and trips on the smallest surge. Aiming for about 80% of rated output leaves room for a forgotten appliance or a real draw higher than the label.
What's the difference between watts (W) and watt-hours (Wh)?
Watts measure power at a given moment: they size the generator or inverter. Watt-hours measure energy over time: they size the battery. A 60 W CPAP used for 8 hours uses 480 Wh.