What a camper trailer air conditioner does and how it differs from home AC

A camper trailer air conditioner cools the inside of your RV by pulling hot air out and pushing cold air back in, just like a home unit. The main difference is size and power: a camper AC is smaller, lighter, and designed to run on limited electricity — either from your trailer's battery, a generator, or shore power when you're parked at a campground with hookups.

Most camper ACs mount on the roof and pull air through a duct system into the living space. Some models are portable units that sit inside, but roof-mounted systems are far more common because they take up no interior space and cool more efficiently. The trade-off is that roof units draw significant power — typically 1,200 to 1,500 watts when running — which is why many camper owners can't run AC and other appliances at the same time.

Understanding this power demand upfront matters because it shapes every other choice you'll make: whether your trailer's electrical system can handle it, whether you need a generator, and how long you can run the unit before draining your battery.

Key Takeaways

  • Camper air conditioners draw 1,200 to 1,500 watts and require either 30-amp or 50-amp shore power, a generator, or a very large battery bank to run reliably.
  • Roof-mounted units are standard in most trailers and cool more effectively than portable models, but installation requires cutting a hole in the roof and running electrical wiring.
  • Your trailer's existing electrical system determines whether you can add AC or upgrade to a larger unit — check your breaker panel and wire gauge before purchasing.
  • Running AC on battery power alone drains a standard camper battery in one to three hours, so most owners use AC only when plugged into shore power or running a generator.
  • Maintenance includes cleaning filters monthly, checking refrigerant levels yearly, and ensuring your roof seal stays intact to prevent leaks.

Types of camper air conditioners and how they're sized

Camper ACs are measured in BTU (British Thermal Units), which describes how much heat the unit can remove per hour. A small trailer or truck camper typically needs 5,000 to 8,000 BTU; a mid-size travel trailer needs 10,000 to 13,500 BTU; and a large fifth wheel or Class A motorhome may need 15,000 BTU or more. The rule of thumb is roughly 400 BTU per 100 square feet of living space, though insulation quality and climate matter — a poorly insulated trailer in Arizona needs more cooling power than a well-insulated one in a mild climate.

The two main types are roof-mounted and portable. Roof-mounted units (also called rooftop or through-wall ACs) are the standard in most new trailers. They're quieter, more efficient, and don't take up floor space. Portable units sit on the floor or a shelf, vent hot air out a window, and are easier to install if you're retrofitting an older trailer, but they're louder and less effective at cooling the whole space evenly.

Some trailers come with a single AC unit; larger ones may have two. Adding a second unit requires upgrading your electrical system and is usually only practical if you're already at a campground with 50-amp service.

Electrical requirements and whether your trailer can handle AC

Before you buy an air conditioner, you need to know what your trailer's electrical system can support. Most campers have one of three setups: 15-amp service (very small trailers), 30-amp service (standard for travel trailers), or 50-amp service (larger trailers and motorhomes). A single AC unit typically draws 13 to 15 amps, which means it will trip a 15-amp breaker and can only run on 30-amp or 50-amp service.

Check your trailer's breaker panel — it's usually in a cabinet near the entrance or in the bedroom. Look at the main breaker and the individual breakers. If your main breaker is 15 amps, you cannot run AC at all. If it's 30 amps, you can run AC but usually nothing else (no microwave, water heater, or other high-draw appliances at the same time). If it's 50 amps, you have more flexibility.

You also need to check the wire gauge running from your breaker panel to the AC outlet or roof unit. Undersized wiring can overheat and create a fire risk. If your trailer is older or was wired for lower power, upgrading the AC may require rewiring, which is a job for an RV electrician, not a DIY project.

Running AC on battery power versus shore power and generators

Running a camper AC on battery power alone is possible but impractical for most owners. A standard camper battery (100 amp-hours) can power a 1,500-watt AC for roughly one to three hours before the battery is too drained to start the engine or run other systems. To run AC for a full day on batteries, you'd need a battery bank of 400+ amp-hours, which costs $3,000 to $8,000 and takes up significant space.

Most camper owners use AC only when plugged into shore power at a campground. Shore power comes in two types: 30-amp (120 volts) and 50-amp (240 volts). A 30-amp connection provides enough power for one AC unit plus limited other appliances. A 50-amp connection provides enough for two AC units, a water heater, microwave, and other devices running simultaneously. Not all campgrounds offer 50-amp hookups, so check before you book.

If you want to run AC while boondocking (camping without hookups), you'll need a generator. A portable generator rated for 4,000 to 6,500 watts can run a single AC unit, though it will be loud and will consume fuel quickly — expect 1 to 2 gallons per hour. Some RV owners install a built-in generator (often called an onboard generator or genset), which runs on propane and is quieter and more convenient, but costs $3,000 to $6,000 to install.

Installation: roof-mounted versus portable and what's involved

Installing a roof-mounted AC requires cutting a hole in your trailer's roof, running electrical wiring from the breaker panel, and sealing everything to prevent leaks. This is not a beginner DIY job. If you're not experienced with electrical work and roof sealing, hire an RV technician. A professional installation typically costs $500 to $1,500 in labor, plus the cost of the unit itself ($400 to $1,200 depending on size and brand).

If you're retrofitting an older trailer that doesn't have AC, the electrician will also need to verify that your breaker panel and wiring can handle the load. If they can't, you may need to upgrade the entire electrical system, which can cost $1,500 to $3,000 or more.

Portable ACs are simpler to install — you just set them on the floor, plug them in, and vent the hot air out a window using a flexible duct. They're a good option if you're renting a trailer or want to avoid roof work, but they're noisier, less efficient, and take up floor space. Most portable units cost $300 to $800.

Maintenance and common problems to watch for

Camper AC maintenance is straightforward if you stay on top of it. Clean or replace the filter every month during the cooling season — a clogged filter reduces cooling power and makes the unit work harder. Check the refrigerant level once a year; if the AC isn't cooling as well as it used to, low refrigerant is often the culprit. Recharging refrigerant requires a technician and costs $150 to $300.

The most common problem is a roof leak around the AC unit. Over time, the sealant around the roof penetration can crack or shrink, allowing water to seep in. Inspect the roof seal every spring and fall, and reseal it if you see any gaps or cracks. Use RV-grade roof sealant (not standard caulk), which flexes with temperature changes and lasts longer.

If your AC stops cooling but the fan runs, the compressor may have failed. This is an expensive repair ($800 to $1,500) and usually means replacing the entire unit rather than repairing it. Running the AC regularly — even in mild weather — helps keep the compressor healthy by circulating refrigerant.

Choosing between upgrading your current AC and adding a second unit

If your trailer already has an AC but it's not cooling well, you have two options: replace it with a larger unit, or add a second one. Replacing is usually cheaper and simpler — you remove the old unit, install the new one in the same location, and use the existing wiring. This costs $800 to $2,000 total (unit plus labor).

Adding a second unit requires running new electrical wiring, installing a second roof penetration, and upgrading your breaker panel to handle the extra load. This is only practical if you have 50-amp shore power available and your trailer's structure can support two roof units. The total cost is typically $2,000 to $4,000.

Before you decide, consider whether the problem is really the AC size or something else — poor insulation, air leaks around windows and doors, or inadequate ventilation can make even a properly sized AC seem weak. Sealing air leaks and improving insulation is often cheaper and more effective than upgrading the AC.

Frequently Asked Questions

Can I run my camper AC while driving?

No. The AC compressor draws too much power for your trailer's alternator to supply while towing. Running it while driving will drain your battery and may damage the electrical system. Turn off the AC before you leave the campground.

What's the difference between a camper AC and a car air conditioner?

A car AC runs on the engine's power and is designed for a small, moving space. A camper AC is stationary, draws much more power, and must run on either shore power or a separate battery and generator system. They use the same basic cooling principle but are built for completely different electrical environments.

How much does it cost to add AC to a trailer that doesn't have it?

The AC unit itself costs $400 to $1,200. Professional installation, including roof work and electrical wiring, costs $500 to $1,500. If your electrical system needs upgrading, add another $1,500 to $3,000. Total: roughly $2,400 to $5,700 depending on your trailer's current setup.

Will running AC drain my fresh water tank?

No. An air conditioner doesn't use fresh water. It does produce condensation as it cools, which drains into a small pan under the unit and typically exits through a drain line outside the trailer. You won't notice this water loss.

What should I do if my AC is leaking water inside the trailer?

The drain line is probably clogged or disconnected. Check under the AC unit (usually accessible from the bedroom or a cabinet) and look for the drain tube. If it's disconnected, reattach it. If it's clogged, flush it with water or use a plumbing snake. If the problem persists, the roof seal may be failing — have an RV technician inspect it.