How Long Will an RV Furnace Run on Propane

The question of how long an RV furnace will run on propane depends on equipment size, BTU output, propane tank capacity, thermostat settings and running conditions. This article breaks down runtime estimates, calculation methods, practical tips to extend run time and safety considerations for RV owners and renters.

Propane Tank Size	Typical Gallons Usable	Common RV Furnace BTU	Estimated Runtime (Hours)
20 lb Cylinder (5 gal)	4.7 gal	20,000 BTU/hr	~6–7 Hours
30 lb Cylinder (7.5 gal)	7.1 gal	20,000 BTU/hr	~9–11 Hours
60 lb Tank (15 gal)	14.3 gal	20,000 BTU/hr	~18–22 Hours

How RV Furnaces Use Propane

Most RV furnaces are forced-air units that burn propane to heat a heat exchanger and then use a fan to distribute warm air. The furnace’s fuel consumption is measured in BTUs per hour, typically ranging from 10,000 to 35,000 BTU/hr for common RV models. Runtime on a propane tank is calculated by dividing available fuel energy by the furnace’s hourly BTU demand.

Key Factors That Determine Furnace Runtime

Furnace BTU Output

Higher BTU furnaces warm spaces faster but consume more propane. A 20,000 BTU/hr furnace uses roughly twice the propane of a 10,000 BTU/hr unit for the same operating hours. Knowing the exact BTU rating is essential for accurate runtime estimates.

Propane Tank Capacity

Propane capacity is usually listed in gallons or pounds. A standard 20 lb cylinder holds about 4.7 gallons of propane when filled to 80% (liquid propane storage rules). Onboard RV tanks commonly range from 5 to 30 gallons or more, and larger tanks substantially extend runtime.

Ambient Temperature And Insulation

Colder outside temperatures increase heat loss through walls, windows and roof, causing the furnace to run more frequently. Well-insulated RVs with thermal curtains or skirting will require less continuous run time than poorly insulated rigs.

Thermostat Settings And Cycling

The thermostat setting controls run cycles. Higher setpoints mean longer and more frequent burns. Furnaces cycle on and off; average duty cycle affects total fuel use. Continuous operation at low settings may be more efficient than frequent short cycles depending on the unit.

Airflow And Duct Efficiency

Restricted airflow from dirty filters, blocked vents or failing blowers reduces heat distribution, prompting longer run times and higher propane use. Proper maintenance preserves efficiency and reduces fuel consumption.

How To Calculate Estimated Runtime

Runtime can be estimated by converting the propane volume into usable BTUs and dividing by the furnace’s BTU/hr rating. The basic formula is: Runtime (hours) = (Gallons Usable × 91,500 BTU/gal) ÷ Furnace BTU/hr. The value 91,500 BTU per gallon is the approximate energy content of liquid propane.

Example: A 20 lb cylinder (~4.7 usable gallons) with a 20,000 BTU/hr furnace: (4.7 × 91,500) ÷ 20,000 ≈ 21.5 hours of theoretical energy. Because furnaces are not 100% efficient and tanks should not be drained completely, practical runtime is usually 60–80% of the theoretical value, or roughly 13–17 hours in this example.

Practical Runtime Estimates For Common Setups

Estimations below assume average conditions: moderate insulation, intermittent cycling to maintain a comfortable indoor temperature and normal blower operation.

• 20,000 BTU/hr furnace with 20 lb cylinder: 6–12 hours depending on thermostat and conditions.
• 20,000 BTU/hr furnace with two 20 lb cylinders or a 30 lb tank: 12–20 hours.
• 20,000 BTU/hr furnace with a 60 lb (15 gal) tank: 18–30 hours.
• 10,000 BTU/hr furnace with 20 lb cylinder: 12–24 hours.

Why Practical Runtime Is Less Than Theoretical

Theoretical calculations assume every BTU of propane turns into delivered heat, but real-world factors reduce efficiency. Heat loss through the RV envelope, inefficiencies in the heat exchanger, pilot light loss and frequent cycling increase propane consumption. Other propane appliances running concurrently (stove, water heater, refrigerator) also reduce available fuel for the furnace.

Tips To Extend RV Furnace Runtime

Improve Insulation And Seal Air Leaks

Sealing gaps, adding weatherstripping and using window coverings can reduce heat loss. Skirting under the RV helps in very cold climates. Even small improvements cut furnace run time significantly.

Lower Thermostat Setpoint And Use Programmable Controls

Reducing the thermostat by a few degrees and using a programmable or smart thermostat to reduce temperature while sleeping or away will reduce propane usage without large comfort tradeoffs.

Maintain The Furnace And Ducts

Cleaning or replacing filters, ensuring the blower works properly and clearing ducts improves efficiency. Regular maintenance should include checking the burner and heat exchanger and calibrating the thermostat for optimal performance.

Use Supplemental Heat Sources

Electric space heaters at campsites with shore power, catalytic heaters or heated blankets reduce furnace dependence. Use safe, manufacturer-recommended supplemental heaters and follow ventilation safety rules.

Preheat While Plugged In

If shore power is available, use electric heating options to reduce propane burn. Preheating the RV before turning off shore power reduces the immediate demand on the furnace once unplugged.

Safety Considerations When Running An RV Furnace

Proper ventilation, working carbon monoxide (CO) and propane detectors and following manufacturer instructions are critical. Furnaces produce combustion gases; blocked vents, cracked heat exchangers or inadequate ventilation can cause CO buildup. Never sleep in an RV with a malfunctioning furnace.

Propane leaks are also hazardous. Regularly inspect hoses, regulators and connections for leaks, and test propane detectors monthly. Know how to shut off propane at the tank in an emergency.

Monitoring Propane Levels And Consumption

Many RVs include gauges on tanks, but these can be inaccurate for weight-based tanks. Weight scales provide exact remaining fuel for portable cylinders. Electronic propane monitors and low-cost tank scales help predict when refills are needed.

Keeping a usage log that notes outside temperature, thermostat setting and runtime helps refine estimates for specific RVs and routes. Over time, users develop reliable expectations for runtime under common conditions.

Common User Scenarios And Estimated Runtimes

Weekend Camping In Moderate Cold

For a couple with a 20,000 BTU furnace and one 20 lb cylinder, expected furnace runtime for overnight and morning use is typically 8–12 hours, enough to keep the RV comfortable during cooler evenings with intermittent use.

Extended Travel In Cold Weather

Travelers in consistently cold climates should either carry larger tank capacity, an additional filled cylinder, or rely on shore power for heat. A 60 lb tank or dual-tank setup offers multiple days of furnace operation depending on temperature and insulation.

Boondocking With Limited Propane

For boondocking, conservative thermostat settings, supplemental non-propane heating options and strong insulation enable multi-day stays on a single cylinder. Users should plan for lower setpoints and staggered heating to extend supply.

How To Choose The Right Furnace And Propane Setup

Select a furnace whose BTU output matches the RV size and intended use. Oversized furnaces add unnecessary propane consumption; undersized units strain to maintain comfort. For frequent cold-weather use, prioritize larger onboard propane capacity or dual-cylinder setups.

Consider fuel monitoring upgrades and insulation investments when deciding on tank size. Those who frequently boondock should choose conservative BTU ratings and carry spare cylinders or invest in an auxiliary heat source.

Useful Calculators And Resources

Propane manufacturers, RV forums and appliance manuals offer BTU tables and calculators. Using the formula outlined earlier and cross-checking with the furnace manual provides the most accurate estimates. RV owner groups often share real-world runtime data for specific models and climates.

Resource	Why It Helps
Propane Education & Research Council	Propane energy values and safety guidance
RV Dealers Association	RV appliance and maintenance best practices
RV Owner Forums	Real-world runtime reports and practical tips

Summary Of Key Recommendations

• Know the furnace BTU rating and the usable gallons of propane available before estimating runtime.
• Use the calculation: (Gallons × 91,500 BTU) ÷ Furnace BTU/hr for theoretical hours, then adjust for efficiency and conditions.
• Improve insulation, maintain equipment and lower thermostat settings to extend runtime.
• Prioritize safety with CO detectors, propane leak checks and proper ventilation.

These guidelines help determine how long an RV furnace will run on propane in practical situations, enabling better trip planning and safer, more comfortable RV living.