What size generator do I need for a travel trailer?

The length of your trailer matters less than one question: do you want to run the air conditioner? Answer that and the rest is easy.

What uses the power in a travel trailer

Trailer load	Running W	Starting W
Roof AC, 13,500 BTU	1,500–2,000	2,800–3,500
Roof AC, 15,000 BTU	2,000–2,500	3,500–4,500
RV fridge (on electric)	150–600	400–1,000
RV microwave	600–1,200	no extra
RV water heater (electric element)	1,200–1,500	no extra
Lights, TV, phone and laptop chargers	20–200 each	no extra

All ranges are from Champion's chart. Westinghouse's manual uses an 11,000 BTU RV AC at 1,010 running and 1,600 extra to start, and an RV fridge at 180 running.

Many trailer fridges and water heaters can run on propane instead. When they do, they take almost nothing from the generator. That's a big help with a small unit.

Size by how you camp

What you run	Running W	Starting W	Look for
Lights, fan, TV, chargers, fridge on propane	under 500	under 1,000	1,000–2,000 W
Add the fridge and water heater on electric	about 2,100	about 2,700	about 3,000 W
One 13,500 BTU AC + lights, TV, chargers	1,830	3,330	2,200 running / 4,000 starting
One 15,000 BTU AC + lights, TV, chargers	2,330	3,830	2,800 running / 4,600 starting
AC + microwave at the same time	about 3,000	about 4,500	3,600 W+ (the limit of a 30 A trailer)

The AC rows use our calculator's figures: 1,500 / 3,000 W for 13,500 BTU and 2,000 / 3,500 W for 15,000 BTU.

Worked example: a 13,500 BTU AC with the basics

• Running: 1,500 (AC) + 100 (lights) + 80 (chargers) + 150 (TV) = 1,830 W
• Biggest surge: the AC, 3,000 − 1,500 = 1,500 W
• Starting: 1,830 + 1,500 = 3,330 W
• With 20% headroom: about 2,200 running and 4,000 starting watts

The calculator above is set up with this list. Swap in the 15,000 BTU AC, or add the microwave, and watch the numbers change.

Trailer size and amp service

Most travel trailers have 30 amp service. That's 30 A × 120 V = 3,600 watts at most, whatever generator you plug in. Some large trailers with two ACs have 50 amp service (up to 12,000 W). For a 30 amp trailer, see what size generator for a 30 amp RV.

A small teardrop or pop-up may use a 15 or 20 amp plug and no AC. A 1,000–2,000 W generator often covers those.

One big generator or two small ones?

Two small inverter generators can link with a parallel kit and act as one bigger unit. A 30 A parallel kit is rated up to 3,600 W, the most a 30 A trailer can use. The upside: you can carry one small unit on quiet weekends and bring both when it's hot. The downside: two engines to maintain.

Soft starts help with the AC

A soft start kit wired into the AC cuts the start-up surge. That can let a smaller generator start the AC. See can a 2,000 watt generator run a 13,500 BTU RV AC?

Do I need an inverter generator for a travel trailer?

You don't need one, but it helps. Inverter generators are usually quieter and lighter, and many can slow down at light loads to save fuel. Many campgrounds have quiet hours and noise rules, so check before you go. Inverters also give cleaner power for the trailer's converter, TV and phone chargers. See inverter vs conventional generator.

What about a small or 25-foot trailer?

Length is only a rough guide. A 25-foot trailer usually has one roof AC and 30 amp service, so the AC rows in the tables above apply. A small trailer with no AC often gets by on 1,000–2,000 W, especially with the fridge on propane.

Heat and altitude

Generators lose power as you go up. Westinghouse's manual says about 3.5% per 1,000 feet, plus about 1% for every 10°F of heat. At 6,000 feet a generator loses about a fifth of its power. At the same time, the AC is working its hardest on hot afternoons. If you camp high or in the desert, size up.

Check your own trailer

• The AC label (on the roof unit, or inside the ceiling shroud) lists BTU and amps. Amps × 120 = running watts.
• The shore cord tells you the service: three prongs is 30 amp, four is 50 amp.
• The fridge and water heater often have switches for "gas" and "electric." Set them to gas when you're on a small generator.
• The microwave's label inside the door lists input watts. It's usually higher than the cooking watts.

Safety: Run it outdoors only, 20+ feet from the house, away from windows and doors. At camp, that means 20+ feet from your trailer and your neighbors', with the exhaust pointed away. Read our carbon monoxide guide.