What Size AC Do I Need for my RV (18-40 ft Class A, B, C, camper & trailer)?

The question – What size AC do I need for my RV – is totally different than sizing a room AC.

Here’s a quick formula – You need 500 to 650 BTUs of AC per foot of RV whether it is a trailer, fifth wheel or motorhome. See the chart below.

RV Air Conditioning BTUs per Square Foot

For the most popular RV sizes – length, widths and heights, you need 60 to 80 BTUs per square foot.

What’s the best AC for RV?

RV AC = 60 to 80 BTUs per square foot

That’s two to four times more than needed for indoor air conditioners – room ACs, central air, etc., which usually need 20-30 BTUs per square foot depending on the climate and house specs.

Our RVs are poorly insulated and have a lot of windows per square feet, so you’ve got to have more AC power for the same size space than you would indoors.

RV AC Sizes

The two most common sizes from Dometic, Coleman, Furrion and other manufacturers are 13,500 BTU and 15,000 BTU.

Less common sizes are 10,500 and 11,000 BTUs plus random sizes from about 5,000 to 15,500 from various brands.

RV AC Size Chart

What size air conditioner for my RV? – a question we get asked a lot.

RV Air Conditioner BTU Size to RV Length Chart

Size of RV Air Conditioner Length of RV
9,000 BTU 18 Feet
10,000 BTU 19 Feet
11,000 BTU 20 Feet
13,500 BTU 22 Feet
15,000 BTU 24 Feet
18,000 BTU 25 – 28 Feet
20,000 BTU 30 Feet
2 AC Units (13500 BTU + 13500 BTU) 32 – 35 Feet
2 AC Units (15000 BTU + 15000 BTU) 35 – 40 Feet

Note:This chart is based on the 8.5 feet width of RV with average insulation. The Chart is also based on an ambient outside temperature of 95F. If the outside temperature is higher than 100F, you need to add additional 20%-30% BTUs to the size of RV AC.

Yes, 95F is pretty hot, but many of us camp in spots that get that warm in the summer months, and it is always better to have a little too much AC than not enough.

15000 BTU RV Air Conditioner

A unit this size is ideal for campers from 16 feet to 24 feet long.

If you have a smaller camper, and smaller units are becoming more popular with higher transportation costs, then this might be a little large. You can run the unit on low, or if you’re still shopping for the right AC, choose a 11,000 to 13,5000 BTU air conditioner.

18000 BTU RV Air Conditioner

We recommend 18000 BTU RV ACs for units from about 22 feet to 30 feet, though the ideal range is for 25 to 28 feet.

13,500 BTU RV Air Conditioner

This is an ideal size for 20 to 24 feet, with 22 feet being the “sweet spot” for a 13,500 BTU RV air conditioner.

RV AC Size Factors

What size AC do I need for my RV? The best way to answer the question is first to use the chart above and then to consider these RV AC size factors.

Where and When you Camp – This is an obvious one. If you’re snowbirds spending winters in a warm place where temperatures range from the 60s to 80s, then our Table above should give you plenty of AC power for the warmest days.

However, if your travel is confined to summer months to fit your work schedule or the kids’ school year, then you likely run into some pretty hot weather wherever you go, from the Adirondacks to historic Gettysburg to the Smokeys to Orlando to Branson, the Grand Canyon or even the higher elevations of Yosemite.

In steamy weather, you won’t regret having a slightly “oversized” RV AC to keep everyone cool.

RV Age – Older RVs often have poorer insulation to start with, or it has slumped down in the walls, or some might have got wet in a leak and compressed, which makes it less effective, or squirrels have torn it out…the list is long of ways the insulation might be sub-par. So, you might want to choose a little more powerful AC than the table shows.

How Many Go – The more warm bodies occupying the RV, the more AC power you need.

RV Air Conditioner Prices

The installed price ranges from $1,300 to $3,500.

RV air conditioner units cost between $900 and $2,400 based on BTU capacity (size), quality and features.

To have the unit installed, expect to pay another $400 to $1,000 or more depending on complexity of the installation, where you live and time of year.

Having the AC installed in the offseason will cost less than during peak season – and during peak times, the waiting list for repairs has been a month to 3 months, even more, the last few years. If you’re in the market for a new RV AC and want something you can DIY, here’s our guide to the best RV air conditioners on the market. It includes a couple portable ACs, one of the best alternatives to a built-in RV AC, and there’s no waiting for installation!

RV Rooftop AC Alternatives

Most of us want AC in our RVs. But there are a few alternatives to consider. You might use one of these as a backup, especially if you find yourself on one of those long waiting lists to have your AC installed or repaired.

Portable ACs – These floor units need to be vented out a window. And their window kits won’t fit in most RV windows. But if you are an RVer, then you know that modifying things to work is a way of life on the road. Plastic, duct tape, a utility knife or small hacksaw, and you’ll get that window kit to fit. Units from 8,000 to 14,000 BTU (Ashrae) are common – though those ratings are outdated, and the US DOE has put out new ratings that are 40% to 50% less.

Fans – A breeze on a sweaty day will evaporate the moisture and cool you down.

Evaporative coolers Ideal for dry climates but not very effective in humid regions, these coolers run air through a wet filter.

Climate Control Tips for Staying Cool

These are pretty straightforward.

  • Park in the shade when possible.
  • Use a sun shield in motorhome windshields.
  • Keep shades down during the day.
  • Open windows at night if the temperature outside is comfortable.
  • Leave the AC on while you are out during the day or leave a couple windows slightly open to allow airflow. The air in the RV will be roughly the same temperature as the outside air when you return, but if you close the unit up tight, the air inside could be much warmer when you get back.


What is the highest BTU RV air conditioner?

15,500 BTUs.

What size generator do I need for RV AC?

A 13,500 BTU RV air conditioner requires 3,800 starting watts and 1,300 running watts.

A 15,000 BTU RV air conditioner needs 5,100 starting watts and 1,600 running watts.

So, choose a generator that gives you the necessary watts to start your RV AC.

Our Guide called How Big of a Generator to Run an AC Unit is a great place to find a specific answer.

How do I measure RV length?

For AC purposes, measure the inside length from front to back. This is also called the floorplan length.

When manufacturers list a RV size, it is the exterior dimensions. If it is a travel trailer, some add in the hitch too.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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