Buying an RV air conditioner without knowing the right BTU rating is one of the most common — and costly — mistakes RV owners make. Too small and it runs constantly without keeping up on hot days. Too large and you've overspent on a unit that short-cycles and wears out faster than it should.
This guide breaks down exactly how to size an RV air conditioner by BTU rating — with a full chart by RV type and length, a simple sizing formula, and our top recommendations so you can buy with confidence.
What Does BTU Mean for RV Air Conditioners?
BTU stands for British Thermal Unit — it's the standard measurement of cooling capacity. The higher the BTU rating, the more heat the unit can remove from your RV per hour. Most RV air conditioners fall into three BTU tiers:
- 13,500 BTU — The most common RV AC size, found on the majority of travel trailers and Class C motorhomes
- 15,000 BTU — The next step up, common on larger rigs and as a second unit on bigger coaches
- 11,000 BTU — Lower-profile units designed for rigs with height restrictions or smaller spaces
Unlike residential air conditioners, RV AC units come in a limited number of standard sizes — so the goal is to match your rig's needs to the closest available BTU tier, not to find a perfect custom fit.
RV Air Conditioner BTU Chart by RV Type and Length
Use this chart as your starting point. Adjust up if you camp in extreme heat or have a dark-colored roof that absorbs more solar heat.
| RV Type | RV Length | Recommended BTU | Notes |
|---|---|---|---|
| Pop-up / Folding Camper | Under 16 ft | 11,000 BTU | Low-profile unit required |
| Small Travel Trailer | 16–22 ft | 11,000–13,500 BTU | Single unit sufficient |
| Mid-Size Travel Trailer | 23–28 ft | 13,500 BTU | Single unit, consider 15,000 for hot climates |
| Large Travel Trailer | 29–35 ft | 15,000 BTU | Or dual 13,500 BTU units |
| Fifth Wheel (mid-size) | 28–34 ft | 15,000 BTU | Dual zone if two-story layout |
| Fifth Wheel (large) | 35 ft+ | Dual 13,500–15,000 BTU | Two units strongly recommended |
| Class B Van | Under 22 ft | 11,000 BTU | Low-profile required for most vans |
| Class C (small) | 22–28 ft | 13,500 BTU | Single unit standard |
| Class C (large) | 29–35 ft | 15,000 BTU or dual 13,500 | Cab-over adds heat load |
| Class A Gas | 32–38 ft | Dual 13,500–15,000 BTU | Most come with two units from factory |
| Class A Diesel Pusher | 38 ft+ | Dual 15,000 BTU | Some large coaches use three units |
How to Calculate Your RV's Cooling Needs
If you want to go beyond the chart, here's the basic formula RV technicians use:
BTU Needed = RV Square Footage × 25 (moderate climate) to 35 (hot/sunny climate)
Example:
- Travel trailer with 300 sq ft of living space
- You camp in the desert Southwest regularly
- 300 × 35 = 10,500 BTU per hour minimum
That puts you squarely in the 13,500 BTU range — which matches the chart recommendation for a mid-size travel trailer in a hot climate. Use the formula to sanity-check the chart, especially if your rig has unusual characteristics like a lot of slide-outs (which add floor space) or heavy window tinting (which reduces heat load).
Factors That Affect How Much Cooling You Need
Climate and Sun Exposure
This is the biggest variable. An RV parked in full sun in Phoenix in July has a dramatically higher heat load than the same rig parked in a shaded campsite in the Pacific Northwest. If you camp in consistently hot, sunny conditions, size up by one tier from the chart recommendation. A dark-colored roof absorbs significantly more solar heat than a white one — factor that in as well.
Number of Occupants
Each person inside your RV generates heat. For a couple, the chart works as-is. If you regularly travel with four or more people, add approximately 1,000–1,500 BTU to your calculation to account for the additional body heat load.
Slide-Outs
Slide-outs increase your usable floor space — and your cooling load. A large slide-out can add 50–80 square feet to your living area. If your rig has multiple slides, use the fully extended floor plan dimensions in your BTU calculation rather than just the base coach length.
Insulation Quality
Newer RVs (roughly 2015 and later) generally have better insulation than older models. If you have an older rig with single-pane windows and thin wall insulation, size up from the chart recommendation — your unit will have to work harder to compensate for heat infiltration.
Roof Color
A white or light-colored roof reflects a significant amount of solar radiation. Dark roofs absorb it. If your RV has a dark roof, bump your BTU estimate up by 10–15% compared to the chart baseline.
Single Unit vs. Dual Units
For rigs over 30 feet, the question often becomes whether to run a single larger unit or two smaller ones. Two units is almost always the better answer for rigs that can support it, for a few reasons:
- Better air distribution: Two units placed front and rear cool the entire length of the coach more evenly than a single unit trying to push cold air 35+ feet
- Redundancy: If one unit fails on a hot trip, the other keeps things livable while you get a repair sorted
- Lower runtime per unit: Each unit runs less hard, which extends the lifespan of both
The trade-off is electrical load — two units require more amperage. On 30-amp service you can typically only run one unit at a time. On 50-amp service, running both simultaneously is standard.
Low-Profile vs. Standard RV Air Conditioners
Standard RV rooftop air conditioners add roughly 12–14 inches of height above the roofline. For campgrounds, storage facilities, and roads with low clearance, this can be a problem. Low-profile units reduce that height to 8–10 inches — a meaningful difference for rigs that push the limits of common clearance restrictions.
Low-profile units are available in 11,000 and 13,500 BTU ratings. If clearance is a concern for your rig, confirm the installed height of any unit before purchasing.
Our Top RV Air Conditioner Picks by Size
11,000 BTU — Dometic Penguin II
The go-to choice for smaller rigs and height-restricted applications. Quiet, reliable, and available in both ducted and non-ducted configurations.
13,500 BTU — Dometic Penguin II / Coleman-Mach 3 Plus
The most popular RV AC size on the market. Both the Dometic Penguin II and Coleman-Mach 3 Plus are proven units with wide parts availability and straightforward installation. The Coleman-Mach 3 Plus is particularly popular for its quiet operation.
15,000 BTU — Dometic Freshjet 5 / Coleman-Mach 15
For larger rigs or hot-climate campers who need maximum cooling capacity. The Dometic Freshjet 5 is a premium option with whisper-quiet operation and strong airflow, while the Coleman-Mach 15 is a proven workhorse at a more accessible price point — both are excellent choices in this tier.
Frequently Asked Questions
Is 13,500 BTU enough for a 30-foot travel trailer?
In moderate climates, yes. In consistently hot conditions — desert camping, full summer use in the South — a 15,000 BTU unit will keep up better. If you frequently camp above 95°F, the extra BTU is worth it.
Can I run two RV air conditioners on 30-amp power?
Not simultaneously. A single 13,500 BTU unit draws roughly 13–15 amps at startup and 8–12 amps running. On 30-amp service, running one unit while managing other loads is the practical limit. For dual-unit operation, 50-amp service is required.
Does a higher BTU air conditioner use more electricity?
Yes, but not proportionally more than the cooling it delivers. A 15,000 BTU unit draws more amperage than a 13,500 BTU unit, but if your rig needs 15,000 BTU to cool properly, a 13,500 BTU unit running constantly will use similar or more power while delivering less comfort.
How do I know if my existing RV AC is the right size?
If your unit runs continuously on hot days without reaching your set temperature, it's likely undersized for your conditions. If it reaches temperature quickly and short-cycles frequently, it may be oversized — though this is less common in RVs given the limited BTU options available.
What is the standard RV air conditioner size?
13,500 BTU is the industry standard, found on the majority of travel trailers, fifth wheels, and Class C motorhomes from the factory. 15,000 BTU is the standard upgrade tier for larger rigs and hot-climate applications.
Find Your RV Air Conditioner at The RV Surplus
We carry Dometic and Coleman-Mach RV air conditioners in all standard BTU sizes at discount prices, with free shipping to the continental U.S. Whether you're replacing a worn-out unit or upgrading to a higher BTU rating, we'll help you find the right fit.
Shop RV Air Conditioners at The RV Surplus →
Already have a unit that's not performing? Check out our RV Air Conditioner Troubleshooting Guide to diagnose the problem before replacing. Questions about sizing or compatibility? Call or text us at 574-218-0549 and we'll point you in the right direction.