Most RVs need a 13,500 BTU air conditioner; larger or hot-climate rigs want 15,000 BTU. As a rule, a single 13,500 BTU unit cools a camper up to about 30 feet in moderate heat, while bigger trailers, desert heat, or poor insulation push you to 15,000 BTU — or a second unit. This guide sizes your AC by length and climate and explains ducted vs non-ducted and the power you'll need to run it.
BTU sizing by camper length
| Camper length | Climate | Recommended AC |
|---|---|---|
| Up to ~25 ft | Moderate | 13,500 BTU |
| ~25–32 ft | Moderate | 13,500–15,000 BTU |
| Any length | Hot / desert | 15,000 BTU (or dual units) |
| 32 ft+ | Any | Two units (zoned) |
Insulation, window area, and shade matter too — a poorly-insulated or sun-exposed rig behaves like a longer camper, so size up if in doubt.
Ducted vs non-ducted
Non-ducted blows from the unit's ceiling shroud — simple, good for single-room campers. Ducted distributes air through ceiling vents for even cooling in larger or multi-zone trailers. Match the new unit to your roof opening (the standard 14×14 vent opening) and your existing duct setup.
Eco-Cool makes this choice explicit with two versions; see Eco-Cool Free Blow vs Ducted V2.
Powering your AC
Air conditioners are heavy loads. On shore power they're easy; to run one off-grid you need a large inverter (typically 3,000W) and a substantial lithium bank, or a soft-start device to tame the startup surge. See RV inverter/chargers and lithium batteries.
Want to skip the inverter? A DC rooftop unit such as the Nomadic Cooling X2 Helix Gen II or X3 Helix fits the same 14×14 opening and runs straight from a 12V or 48V lithium bank. See which Nomadic DC air conditioner fits and how much battery it needs.
Our picks by use-case
- Standard camper, moderate climate: 13,500 BTU non-ducted.
- Larger / hot climate: 15,000 BTU, ducted if multi-zone.
- Off-grid cooling: 13,500 BTU + soft start + 3,000W inverter + large lithium bank.
FAQ
Is 13,500 or 15,000 BTU better for my RV?
13,500 BTU suits most campers in moderate heat; choose 15,000 BTU for larger rigs, hot climates, or poor insulation.
Can I run my RV AC off battery?
Yes, with a large (≈3,000W) inverter, a big lithium bank, and ideally a soft-start device — but runtime is limited; shore power or a generator is easier for long use.
Will a new AC fit my roof opening?
RV AC units use the standard 14×14 roof opening, so most are a direct swap — confirm ducted vs non-ducted matches your setup.
Replacing a roof fan instead? OutEquipPro sizes the 12V, 24V and 48V Summit 2 for a 14.1 x 14.1 inch roof fan opening in roofs 1.5 to 3.5 inches thick; see installing a Summit 2 in a 14x14 roof vent opening.
Do I need a soft start?
A soft start reduces the compressor's startup surge, making it far easier to run an AC on an inverter or a smaller generator.
Stay cool: shop RV air conditioners & parts — in stock, ships from Upland, CA.
Related guides
Related reading
Sizing a battery-powered portable unit works differently from a rooftop AC:
Shop the parts in this guide
- Dometic Penguin II 15,000 BTU Rooftop RV AC, Black (640315CXX1J0)
- Zero Breeze Mark 3 Portable Air Conditioner, 5280 BTU
- Cybertake S2 Pro Portable Camping Air Conditioner, 5100 BTU
- Cybertake S1 Pro Portable Camping Air Conditioner, 4100 BTU
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