RV generator size calculator (30 amp and 50 amp)
Pick the rig’s service, how many air conditioners must run and what else is on at the same time. The air conditioner’s start is usually what decides the generator.
Enter your measurements
More options: Headroom
- Running watts
- 3,250 W
- Starting watts
- 4,100 W
- Running watts, all together
- 2,600 W
- Most your RV service can draw
- 3,600 W
- Share of the service in use
- 72%
1 × 2,000 W AC + 600 W other = 2,600 W running × (1 + 25%) = 3,250 W
Starting: 2,600 W + one AC start (3,500 − 2,000 W) = 4,100 W
30 A service: 120 V × 30 A = 3,600 W
- Look for a generator with a TT-30R outlet (120 V, 30 A), or use the correct adapter from a 120/240 V outlet. Plug in through a surge protector.
Quick answers for common sizes
| Example | Answer |
|---|---|
| What size generator for a 30 amp camper | 3,250 W running / 4,100 W starting |
| What size generator for a 50 amp RV with 2 AC units | 8,125 W running / 8,500 W starting |
Generator size by number of air conditioners
| Air conditioners running | Running watts | Starting watts | Share of the service in use |
|---|---|---|---|
| 0 | 750 W | 750 W | 17% |
| 1 | 3,250 W | 4,100 W | 72% |
| 2 | 5,750 W | 6,100 W | 128% |
| 3 | 8,250 W | 8,250 W | 183% |
Worked examples: what size generator for a 30 amp camper and what size generator for a 50 amp RV with 2 AC units. The difference between the two services is explained in 30 amp vs 50 amp RV.
The watt math
30 A service = 120 V × 30 A = 3,600 W 50 A service = 2 legs × 120 V × 50 A = 12,000 W generator running W ≥ (AC running + everything else) × (1 + headroom) generator starting W ≥ running total + one AC’s start-up extra
A 30 A RV plug (NEMA TT-30) carries a single 120 V circuit, so the most the rig can draw is 3,600 W. A 50 A RV plug (NEMA 14-50) carries two 120 V legs of 50 A each — 6,000 W per leg, 12,000 W in all. Champion’s generator specs show the matching outlets: its 3500 W model has a 120 V 30 A TT-30R RV outlet, and its 8500 W inverter a 120/240 V 14-50R.
Why the air conditioner decides it
| RV air conditioner | Running W | Starting W |
|---|---|---|
| 13,500 BTU | 1,500–2,000 | 2,800–3,500 |
| 15,000 BTU | 2,000–2,500 | 3,500–4,500 |
Everything else in an RV is small by comparison — except the microwave (600–1,200 W), an electric water heater element and a hair dryer. Run them while the AC is cycled off and a smaller generator copes.
Practical tips
- Altitude and heat reduce output. A generator makes less power high up and in hot weather — one reason for headroom. The manual gives the derating.
- Two inverter generators in parallel can add up to the output of a bigger one; many parallel kits include an RV outlet.
- Run the generator downwind and away. Exhaust next to a slide-out or an open window is how CO gets inside your RV. CPSC’s guidance for homes is at least 20 feet away, pointed away from doors, windows and vents; give your rig — and your neighbors’ — the same room.
- Keep a CO alarm in the RV. CPSC recommends battery-powered CO alarms whenever a generator runs; test them before every trip.
- Use a surge protector between the generator and the RV cord.
What you’ll need
- Inverter generator (about 2,000–3,500 W)Premium price
Quieter and more fuel-thrifty at light loads than an open-frame generator, with clean power for electronics. Many have a 30 A RV outlet.
See options on Amazon (opens in a new tab) - 30 A RV surge protectorMid-range price
Plugs in between the pedestal or generator and your RV cord to catch wiring faults and voltage spikes before they reach the rig.
See options on Amazon (opens in a new tab) - 50 A RV surge protectorMid-range price
The 50 A version for rigs with two 120 V legs. Some models also flag low voltage from a struggling generator.
See options on Amazon (opens in a new tab) - Battery-operated carbon monoxide alarmBudget price
CPSC advises battery or battery-backup CO alarms whenever a generator is in use. Look for UL 2034 certification and test monthly.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What size generator for a 30 amp camper?
With one 13,500 BTU air conditioner and about 600 W of other loads, about 3,250 running and 4,100 starting watts at the top of Champion’s ranges — a 3,500–4,000 W-class generator. Without the AC, about 2,000 W is plenty. See what size generator for a 30 amp camper.
What size generator for a 50 amp RV with 2 AC units?
Two 15,000 BTU units (2,500 W running each, top of Champion’s range) plus 1,500 W of other loads is 6,500 W running — about 8,125 W with 25% headroom — and about 8,500 W at the moment one AC starts. See what size generator for a 50 amp RV with 2 AC units.
How many watts can a 30 amp RV use?
3,600 W: 120 V × 30 A. A 50 A RV can use up to 12,000 W across its two 120 V legs.
Can a 2000 watt generator run a 30 amp RV?
It can run the lights, fridge, outlets and battery charger. Most RV air conditioners need more starting watts than a single 2,000 W generator gives (Champion: 2,800–3,500 for a 13,500 BTU unit); two paralleled, or a soft-start on the AC, are the common fixes.
Related guides
Sources
- Champion Power Equipment — Generator Wattage Chart (opens in a new tab) — Typical running and starting watts for household, RV and job-site appliances (a manufacturer’s planning chart — your nameplate wins).
- Champion Power Equipment — 3500-Watt Dual Fuel Generator (model 201213) specifications (opens in a new tab) — 3,500 running / 4,000 starting watts on gasoline; 14 h at 50% load on 4.7 gal; 10.5 h at 50% load on a 20 lb propane tank; 120 V 30 A TT-30R RV outlet.
- Champion Power Equipment — 8500-Watt Dual Fuel Inverter (model 201175) specifications (opens in a new tab) — 120/240 V 14-50R outlet — the plug shape a 50 A RV uses.
- U.S. Consumer Product Safety Commission — Portable Generator Hazards (Safety Alert 5123, 2021) (opens in a new tab) — Never run a generator indoors or in a garage, even with doors open; place it outside far from doors, windows and vents; CO alarms; never “backfeed” by plugging into a wall outlet.
- U.S. Consumer Product Safety Commission — CPSC Warns Consumers in Path of Storms to Take Precautions When Using Portable Generators (July 24, 2020) (opens in a new tab) — “Use your generator OUTSIDE your house ONLY, at least 20 feet from your home”; make sure you have working CO alarms.