What size generator do I need for a 30 amp RV?

"30 amp" is the most confusing number in RV power. It describes your RV's plug and wiring, not the generator you need. Once you see what it really means, sizing gets easy.

What "30 amp" really means

A 30 amp RV has one 120 V line rated for 30 amps. Watts = volts × amps, so:

30 A × 120 V = 3,600 watts.

That's the most your RV's main breaker will let through. It's a ceiling. You don't need a 3,600 W generator, and a bigger one won't push more than 3,600 W into a 30 amp RV. What you need depends on what you run at the same time.

For comparison, a 50 amp RV has two 120 V lines of 50 A each: 50 × 120 × 2 = 12,000 watts.

What's using the power in your RV

Here's what the makers' charts say about the big RV loads:

RV appliance	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
TV, lights, chargers	50–200 each	no extra

All from Champion's chart. Honda's chart lists a 13,500 BTU RV AC at 1,800 running and 2,800 starting. Our calculator uses 1,500 / 3,000 W for 13,500 BTU and 2,000 / 3,500 W for 15,000 BTU.

The AC is the big one. It sets your generator size.

Worked example: one AC plus the basics

A 13,500 BTU roof AC, LED lights, a TV and phone chargers:

• Running: 1,500 (AC) + 100 (lights) + 150 (TV) + 80 (chargers) = 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

Now add the microwave while the AC runs, and you're near 3,000 running watts. That's close to the RV's 3,600 W limit and more than most small generators give. The easy fix: don't run the microwave and AC at the same time.

Quick sizing guide for a 30 amp RV

How you camp	Size to look for
No AC: lights, fridge, fan, TV, chargers	About 2,000 W
One 13,500 BTU AC with a soft start	2,000–2,500 W can work, with little else on
One 13,500 BTU AC, no soft start	About 3,000–4,000 W
One 15,000 BTU AC	About 3,500–4,500 W
AC and microwave at the same time	3,500 W+ running (you'll hit the RV's 3,600 W limit)

The tool above checks an AC against a generator. It's set to a 13,500 BTU AC with no soft start and a generator rated 3,000 running / 3,500 starting. Change the numbers to match yours.

Soft starts change the math

A soft start kit is a small box wired into the AC. It eases the compressor on instead of slamming it on. The maker of one popular kit says it can "reduce your current by up to 75%" at start-up, and its site carries customer reports of a 13,500 BTU AC starting on a single 2,000 W class inverter. Results vary with heat and altitude, but a soft start is often cheaper than a bigger generator. See can a 2,000 watt generator run a 13,500 BTU RV AC?

Can a 30 amp RV run two air conditioners?

Not at the same time, in most cases. Two 13,500 BTU ACs need about 3,000 running watts together, before lights or the fridge. That's right at the RV's 3,600 W limit, and the second AC's start-up would push it over. RVs with two ACs usually have 50 amp service for this reason.

Plugs and cords

• TT-30 is the 30 amp RV outlet. Many generators have one built in.
• L5-30 is a 30 amp twist-lock outlet on some generators. An L5-30 to TT-30 adapter is rated 120 V, 30 A, 3,600 W.
• Don't plug a 30 amp RV into a 14-50 (50 amp) outlet without the correct adapter. The RV's own breaker still limits it to 30 A.

More detail: 30 amp vs 50 amp generator cords.

Camping up high or in the heat?

Generators lose power with altitude. Westinghouse's manual says output drops about 3.5% for every 1,000 feet, and about 1% for every 10°F of extra heat. At 5,000 feet, a 3,500 W generator acts more like 2,900 W. Size up if you camp in the mountains.

Check your own RV

• Look at the AC's label (inside the ceiling shroud or on the roof unit) for BTU and amps.
• Look at the shore power cord. Three prongs means 30 amp; four means 50 amp.
• Check the microwave's input watts on the label inside the door. It's often higher than the cooking watts.

Safety: Run it outdoors only, 20+ feet from the house, away from windows and doors. At a campsite, keep it well away from your RV's and your neighbors' windows and vents. Read our carbon monoxide guide.