What Size RV Furnace Do I Need?
Choosing the correct RV furnace size is important for staying comfortable without wasting propane or overworking your heating system.
RV furnaces are typically sized by BTU output (British Thermal Units). The higher the BTU rating, the more heat the furnace can produce.
Most RV furnaces range from:
- 16,000 BTU
- 20,000 BTU
- 25,000 BTU
- 30,000 BTU
- 35,000 BTU
- 40,000 BTU
The right size depends on your RV’s size, insulation, layout, and the climate where you camp.
General RV Furnace Size Guide
Here is a rough guideline many RV owners use:
| RV Length | Common Furnace Size |
|---|---|
| Small camper / teardrop | 16,000–20,000 BTU |
| Small travel trailer | 20,000–25,000 BTU |
| Mid-size travel trailer | 25,000–30,000 BTU |
| Large travel trailer / fifth wheel | 30,000–35,000 BTU |
| Large fifth wheel / motorhome | 35,000–40,000 BTU |
These are only general estimates. Actual heating needs vary significantly.
Factors That Affect RV Furnace Size
RV Size and Layout
Larger RVs naturally require more heat output.
Slide-outs, high ceilings, and open floorplans can also increase heating demands.
Climate
If you camp mostly in mild weather, a smaller furnace may be sufficient.
If you regularly camp in freezing temperatures, you may need a larger furnace.
Insulation Quality
Well-insulated RVs retain heat better and require less furnace runtime.
Poor insulation can make even large furnaces struggle in cold weather.
Number of Occupants
More people inside the RV generate additional heat, which can slightly reduce furnace demand.
Can an RV Furnace Be Too Large?
Yes.
An oversized RV furnace may:
- Short cycle frequently
- Use more propane
- Create uneven temperatures
- Wear components faster
- Produce louder heating cycles
Proper sizing helps maintain more consistent comfort and efficiency.
Can an RV Furnace Be Too Small?
Also yes.
An undersized furnace may:
- Run constantly
- Struggle to maintain temperature
- Use excessive propane trying to keep up
- Wear out faster due to continuous operation
Replacing an Existing RV Furnace
In many cases, the easiest option is replacing your furnace with the same BTU size originally installed by the manufacturer.
Popular RV furnace sizes include:
- Suburban SF-20 → 20,000 BTU
- Suburban SF-30 → 30,000 BTU
- Suburban SF-35 → 35,000 BTU
- Dometic / Atwood AFMD and AFSD series
- Dometic / Atwood 7900 and 8500 series
When upgrading or replacing a furnace, you should also verify:
- Duct sizing
- Cabinet opening dimensions
- Gas line configuration
- Voltage requirements
- Venting compatibility
Signs Your RV Furnace May Be the Wrong Size
Furnace Too Small
- RV never fully warms up
- Furnace runs constantly
- Cold spots throughout RV
Furnace Too Large
- Furnace turns on and off frequently
- Uneven heating
- Excessive propane usage
- Temperature swings
Common RV Furnace Brands
At RV Furnace Guys, we carry furnaces and replacement parts for:
- Suburban RV furnaces
- Dometic / Atwood RV furnaces
We also carry common replacement components including:
- Control boards
- Sail switches
- Igniter electrodes
- Gas valves
- Thermostats
- Blower motors
FAQ
What size furnace is common in an RV?
Most RV furnaces fall between 20,000 and 35,000 BTUs.
How do I know what size furnace my RV has?
The furnace model sticker usually lists the BTU rating.
Can I install a larger furnace in my RV?
Sometimes, but ducting, cabinet size, propane supply, and venting must all be compatible.
Does a bigger RV furnace use more propane?
Yes. Higher BTU furnaces generally consume more propane when running.
Should I replace my RV furnace with the same size?
In many cases, yes. The RV manufacturer typically sized the furnace for the RV’s layout and duct system.