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Key takeaways
- Diesel air heaters usually draw much less 12V power while running than RV furnace blowers. Webasto lists 1.25 to 2.45 A for its Air Top 2000 STC.
- RV furnaces draw roughly 3 to 12.5 A depending on the model, per Suburban and Atwood service manuals.
- Diesel heaters draw more at startup while the glow pin heats, so frequent on-off cycling reduces their advantage.
- Furnaces are built into the RV and heat ducted spaces and tank bays. Diesel heaters need a proper install with exhaust, intake and fuel supply.
- Choose a diesel heater for long winter boondocking in vans and small rigs. Stick with the furnace if you need ducted heat to the whole RV and basement.
Quick verdict
A diesel air heater uses far less battery power while running than most RV furnace blowers. That makes it attractive for winter boondockers, especially in vans and small trailers. But the furnace is already installed, heats ducted spaces and basement tank bays in many RVs, and runs on the propane you already carry. For most trailer and motorhome owners, the furnace stays. A diesel heater is an add-on for long, cold, off-grid stays where battery budget matters most.
This page compares power and fuel. For furnace repair, see RVgear's RV furnace troubleshooting guide. For diesel heater picks and installation, see SolarCabin's best diesel heaters and diesel heater sizing and install guide.
Side-by-side comparison
| Factor | RV propane furnace | Diesel air heater |
|---|---|---|
| 12V draw while running | About 3 to 12.5 A per Suburban and Atwood manuals | Webasto lists 1.25 to 2.45 A for the Air Top 2000 STC |
| Startup draw | Blower and igniter at start | Higher for a few minutes while the glow pin heats |
| Fuel | Propane | Diesel (from its own tank or the vehicle tank) |
| Heat distribution | Ducted to living space, often to tank bays | Usually one or a few outlets |
| Noise | Blower and burner noise inside | Fan noise inside, pump ticking and exhaust outside |
| Installation | Factory installed | Needs exhaust, intake, fuel line and mounting |
| Price tier to add | Already in most RVs | $–$$$ depending on brand |
Power draw
This is where diesel heaters win clearly.
RV furnaces: Suburban's service manual lists roughly 2.8 to 11.5 A across its NT and SF models, and Atwood's lists 4.6 to 9.8 A for the 8500 series and up to 12.5 A for its largest DC furnace. See our RV furnace battery draw guide for how to measure yours.
Diesel heaters: Webasto's published specs for the Air Top 2000 STC list 1.25 to 2.45 A (14 to 29 W), depending on heat output. Other brands publish their own figures. Check the manual for the heater you're considering.
The catch is startup. Diesel heaters use a glow pin to ignite the fuel, and it draws more current for a few minutes each time the heater starts. Heaters that run steadily on a low setting use far less energy than ones switching on and off all night.
Worked example
Say a furnace blower draws 8 A (an example value within the published range) and runs 5 hours of a cold night: 8 × 5 = 40 Ah.
A diesel heater running 10 hours at an average of 2 A (an example within Webasto's listed range, before startup draw): 2 × 10 = 20 Ah, plus a little extra for startup.
In this example, the diesel heater uses about half the battery power while running twice as many hours. Your numbers will differ, so measure with a battery monitor.
Fuel use
Furnace: A 30,000 BTU furnace (example) with the burner on for 3 hours burns about 90,000 BTU, or roughly 1 gallon of propane. The U.S. Energy Information Administration lists propane at about 91,500 BTU per gallon.
Diesel heater: Webasto lists 0.03 to 0.06 gallons per hour for the Air Top 2000 STC. Running 10 hours at the high end is about 0.6 gallons.
Diesel heaters let you save propane for cooking and hot water, which can stretch time between refills.
Noise and comfort
Furnaces are loud when they cycle on, and the start-stop pattern can wake light sleepers. Diesel heaters running steadily on low are usually quieter inside, though the outside fuel pump ticks and the exhaust makes some noise. Consider your neighbors at crowded LTVAs and campgrounds.
Diesel heaters produce dry heat. Furnaces heat the whole ducted system, including basement tank bays on many models, which matters for freeze protection. See RVgear on living in an RV in winter.
Installation and safety
The furnace is already installed. A diesel heater needs a secure mount, a sealed combustion air intake, an exhaust routed safely outside, a fuel supply and a fused electrical connection. Poor installation can let exhaust into the living space. Follow the heater maker's installation manual exactly, or have a qualified installer do it. Keep working CO and LP detectors either way.
Some diesel heaters need altitude adjustment or a high-altitude setting to run well at elevation. Check the manual if you camp high.
Bluetti power stations
All-in-one LiFePO4 power stations with built-in inverter, charger and solar input. Compare current models and bundles on Bluetti's own store.
See Bluetti modelsRenogy components
Panels, MPPT charge controllers, DC-DC chargers and lithium batteries for custom builds. Check specs and current kits on Renogy's store.
Shop Renogy gearChoose the furnace if
- You need ducted heat throughout a larger RV.
- Your tank bays depend on furnace heat to avoid freezing.
- You camp at hookups often, or can run a generator to recharge.
- You don't want to modify your RV.
Choose a diesel heater if
- You boondock for long stretches in cold weather.
- Your battery bank or solar is modest and the furnace drains it overnight.
- You have a van or small rig without ducted heat needs.
- You want to save propane for cooking and hot water.
Many winter boondockers use both: the diesel heater for steady overnight warmth and the furnace for quick warmups and tank-bay protection. For the full winter power plan, see our snowbird RV solar guide.
Frequently asked questions
Does a diesel heater use less battery than an RV furnace?
Usually, yes, while running. Webasto lists 1.25 to 2.45 A for its Air Top 2000 STC, while RV furnace blowers run roughly 3 to 12.5 A per Suburban and Atwood service manuals. Diesel heaters draw more briefly at startup.
How much fuel does a diesel heater use?
It depends on the model and setting. Webasto lists 0.03 to 0.06 gallons per hour for the Air Top 2000 STC. Check the manual for the heater you're considering.
Can I install a diesel heater in my RV myself?
It requires a secure mount, a sealed exhaust, an air intake, a fuel supply and fused wiring. Follow the maker's installation manual exactly or have a qualified installer do it, and keep working CO detectors.
Is a diesel heater quieter than an RV furnace?
Inside, a diesel heater running steadily on low is often quieter than a cycling furnace. The outside fuel pump and exhaust make some noise, so consider neighbors.
Should I replace my RV furnace with a diesel heater?
Most owners add a diesel heater rather than replace the furnace, because the furnace provides ducted heat and often warms tank bays. Using both gives you options.