RV air conditioning keeps your living space cool, but the type you need depends on where you mount it and how much cooling power your rig requires

RV air conditioners fall into two main categories: rooftop units and window or portable units. A rooftop unit sits on top of your RV and cools the entire interior through ducting, while window and portable units cool a single room or section. Rooftop units are the most common in travel trailers and motorhomes because they don't take up interior space and work while you're driving. Window units and portable models are cheaper upfront but take up living space and only work when you're parked and plugged into shore power.

The cooling capacity of an AC unit is measured in BTU (British Thermal Units). A small RV bedroom might need 5,000 to 8,000 BTU, while a full-size motorhome or travel trailer typically needs 13,500 to 15,000 BTU. Larger rigs sometimes have two rooftop units. Choosing the wrong size means either wasting money on more power than you need or running the unit constantly without reaching your target temperature.

Key Takeaways

  • Rooftop AC units are built into most RVs and cool the whole interior, while window and portable units are cheaper but only cool one room and require shore power.
  • BTU (British Thermal Units) measures cooling power; most RVs need between 8,000 and 15,000 BTU depending on size and insulation.
  • Rooftop units draw significant electrical power, so you need to know your RV's amp service (30-amp or 50-amp) before replacing one.
  • Maintenance includes cleaning filters monthly during cooling season and checking refrigerant levels annually to prevent breakdown during travel.
  • Aftermarket rooftop units cost $1,500 to $3,500 installed, while window units run $300 to $800.

Rooftop units: how they cool your entire RV

A rooftop AC unit pulls warm air from inside your RV through a return duct, cools it using refrigerant, and pushes the cooled air back through ceiling vents. The hot air it removes is expelled outside. Because the unit sits on the roof, it doesn't compete with your living space, and it runs on your RV's main electrical system rather than a separate outlet.

Rooftop units come in two styles: standard and low-profile. Standard units are taller and stick up noticeably on the roof; low-profile models are flatter and more aerodynamic. Low-profile units cost more but reduce wind noise and drag at highway speeds. Both types mount through a roof opening and connect to your RV's electrical panel and ductwork.

Most travel trailers and fifth wheels come with one rooftop unit as standard. Larger motorhomes and trailers often have two units, one in the bedroom and one in the living area, so you can cool different zones independently. If your RV has only one unit and you want to add a second, you'll need to verify your electrical system can handle the extra load.

Window and portable units: lower cost, limited coverage

Window units mount in a side window or exterior wall opening and cool the room they're installed in. Portable units sit on the floor or a shelf, draw air from the room, cool it, and return it through a duct that vents outside. Both types are significantly cheaper than rooftop units and don't require roof work or permanent installation.

The trade-off is that window and portable units only work when you're parked and connected to shore power—they draw too much current to run on battery alone. They also take up valuable interior space in an RV, where every square foot counts. Window units can reduce natural light and ventilation, and portable units need floor space and a clear path for the exhaust duct.

Window and portable units work well as a backup to a failing rooftop unit or as a supplement in a bedroom that doesn't cool evenly. They're also the only option if your RV's roof can't support additional weight or if you rent and can't modify the structure.

Electrical requirements and power draw

RV electrical systems come in two standard sizes: 30-amp and 50-amp service. A 30-amp system provides 3,600 watts total; a 50-amp system provides 12,500 watts. A single rooftop AC unit typically draws 10 to 15 amps (1,200 to 1,800 watts), which is manageable on either system but leaves little room for other appliances.

If your RV has two rooftop units or you want to run the AC while using your water heater, microwave, or other high-draw appliances, you need to know your total available power. Running two AC units simultaneously on a 30-amp system will trip your breaker. On a 50-amp system, you can run two units and most other appliances, but not everything at once.

When replacing a rooftop unit, confirm your RV's amp service before ordering. The replacement unit should match or be slightly lower in amp draw than the original. If you want to upgrade to a larger unit, you may need to upgrade your electrical panel, which is expensive and requires professional installation.

Maintenance to keep your AC running

The most important maintenance task is cleaning or replacing the air filter monthly during cooling season. A clogged filter forces the unit to work harder, reduces cooling efficiency, and can damage the compressor. Filters are inexpensive and take five minutes to swap out.

Check the refrigerant level annually before your cooling season starts. Low refrigerant means the unit won't cool properly and can damage the compressor if it runs dry. A technician can check this with a gauge and top it off if needed. This is not a do-it-yourself task because refrigerant is pressurized and requires certification to handle.

Inspect the roof seal around the AC unit each spring and fall. Caulk can crack from sun exposure and temperature changes, allowing water to leak into your RV. If you notice soft spots in the roof around the unit or water stains on the ceiling below, have a technician inspect and reseal it when ready. Water damage spreads quickly in an RV and is expensive to repair.

Keep the exterior of the rooftop unit clean. Dust, leaves, and debris block airflow and reduce cooling power. Brush off the top and sides with a soft brush when you're parked. Don't use a pressure washer, which can damage the fins and seals.

Replacing a rooftop unit: what to expect

If your rooftop AC stops cooling or makes unusual noises, replacement is usually the most practical option. Repair costs can run $500 to $1,500 depending on the problem, and an older unit may fail again soon after. A new rooftop unit costs $1,500 to $3,500 installed, depending on the brand, BTU rating, and whether it's standard or low-profile.

Installation requires removing the old unit, cleaning and inspecting the roof opening, installing the new unit, resealing the roof, and reconnecting the electrical and duct connections. This typically takes four to eight hours and should be done by an RV technician or service center. Some RV dealers offer installation as part of the purchase.

When choosing a replacement, match the BTU rating of your original unit unless you have a specific reason to go larger. Going significantly larger won't cool faster—it will just cycle on and off more frequently and waste energy. Stick with established brands like Dometic, Coleman, or Carrier, which have parts and service support at most RV service centers.

Troubleshooting common AC problems

If your AC runs but doesn't cool, the refrigerant may be low, the filter may be clogged, or the compressor may be failing. Start by checking and cleaning the filter. If that doesn't help, have a technician check the refrigerant level and compressor function. Don't run the unit continuously if it's not cooling—you risk damaging the compressor.

If the AC won't turn on at all, check that your RV is plugged into shore power and that the breaker for the AC circuit hasn't tripped. Look at your electrical panel and flip the AC breaker off and back on. If it trips again when ready, there's an electrical fault and you need a technician. If it stays on, try the AC again.

If the AC is noisy or vibrating, the mounting bolts may be loose, or internal components may be failing. Tighten the bolts on the roof if you can access them safely. If the noise continues, have a technician inspect it. Unusual sounds often mean the unit is close to failure.

If you see water dripping inside your RV near the AC unit, the condensation drain line may be clogged. This line runs from the unit to the exterior and can get blocked by dust or debris. A technician can flush it out, or you can try using compressed air to blow it clear from outside.

Frequently Asked Questions

Can I run my RV air conditioner on battery power?

No. A rooftop AC unit draws 10 to 15 amps continuously, which would drain a typical RV battery bank in under an hour. AC units require shore power (plugged into a campground pedestal) or a generator large enough to handle the load—usually 5,000 watts or more. Window and portable units have the same requirement.

How much does it cost to add a second AC unit to my RV?

A second rooftop unit costs $1,500 to $3,500 installed, depending on the brand and BTU rating. Before adding one, verify your electrical system can handle it. A 30-amp system cannot run two units simultaneously. A 50-amp system can, but you won't be able to run other high-draw appliances at the same time.

What's the difference between a standard and low-profile rooftop unit?

Standard units are taller and stick up more on the roof; low-profile units are flatter and more aerodynamic. Low-profile units reduce wind noise and drag at highway speeds and look sleeker, but they cost $300 to $500 more. Both cool equally well. The choice depends on your priorities and budget.

How often should I service my RV air conditioner?

Clean or replace the filter monthly during cooling season. Have the refrigerant level checked and the roof seal inspected annually before summer. If the unit is over 10 years old, consider having a technician do a full inspection to catch problems early.

Can I install a rooftop AC unit myself?

Installation requires cutting or enlarging a roof opening, working at height, handling pressurized refrigerant, and making electrical connections to your RV's panel. This is not a do-it-yourself job. Improper installation can damage your roof, void your warranty, and create safety hazards. Use a certified RV technician.