Heating & appliances
Propane furnaces: efficiency, sizing and care
A propane furnace burns propane to heat air and a blower pushes that air through your ducts, and its efficiency is rated by AFUE, the share of fuel turned into heat over a season. For a replacement, compare AFUE, have the contractor size the unit to your home's heat loss rather than the old furnace's label, and plan a yearly check of the burner, venting and system.
Updated · American River Gas office, Newcastle
How a propane furnace heats your home
When the thermostat calls for heat, the furnace lights its burners, hot combustion gases pass through a heat exchanger, and a blower moves house air across the outside of that exchanger and into the ducts. The combustion gases never mix with the air you breathe. They leave through a vent pipe to the outdoors.
Propane furnaces are common in foothill homes beyond the natural gas mains, and many homeowners like the steady, warm air they deliver on cold nights.
What AFUE tells you
Annual Fuel Utilization Efficiency (AFUE) is the percentage of the fuel's energy that ends up as heat in your home over a typical season. The higher the number, the less propane the furnace needs for the same warmth. ENERGY STAR certified gas furnaces have higher AFUE ratings and more efficient blower motors than standard models, and certified models are up to 16 percent more efficient than standard models in California's climate region, according to ENERGY STAR.
Standard versus condensing furnaces
- Standard (non-condensing) furnaces send hot exhaust up a metal vent. They can be a simpler swap where an existing vent is already in place.
- High-efficiency condensing furnaces pull extra heat from the exhaust, cooling it enough that water condenses out. They usually vent through plastic pipe out a side wall or roof and need a drain for the condensate.
- The higher AFUE of a condensing unit means less propane used per season. Your HVAC contractor can tell you whether your home's venting and drain options fit one.
Sizing a replacement
Bigger is not better with furnaces. An oversized unit heats in short bursts, cycles on and off, and wears faster. Ask your contractor for a load calculation based on your home's size, insulation, windows and air leakage, especially if you have added insulation or new windows since the old furnace went in.
Also think about the rest of the house. A furnace that runs on propane often pairs with a propane water heater, range and fireplace. The total load is what sets your gas line and tank size, so a change in one appliance is a good time to check the whole system.
Where the furnace sits matters
Propane is heavier than air. California's Mechanical Code restricts propane appliances in pits, basements and similar low spots, and an under-floor furnace needs an approved way for unburned gas to escape. Placer County's propane appliance handout shows the details, including the screened foundation drain and access space. Your permit office confirms what applies to your home.
Power outages and furnaces
A propane furnace needs electricity for its blower, igniter and controls, so it stops during a power outage unless it has backup power. Many foothill homes keep a propane fireplace that can run without power as a backup heat source.
Yearly care
- Change or clean the filter on the schedule in the owner's manual, more often during smoky fire seasons.
- Keep the area around the furnace clear of storage.
- Have a qualified technician check the burners, heat exchanger, venting and controls before the heating season.
- Install carbon monoxide alarms on every level and outside sleeping areas, as the U.S. Consumer Product Safety Commission recommends.
Installing a new furnace
Any time a new appliance is connected, the gas system gets a leak test, and each appliance needs its own shut-off valve within 6 feet. Let us know before a furnace swap so the delivery schedule and your tank size keep up with the new unit. If you smell gas, leave the building first, then call 911 and us from outside.
Questions
Straight answers
What is a good AFUE for a propane furnace?
Higher is better. ENERGY STAR certified gas furnaces have higher AFUE ratings than standard models, and condensing furnaces are the high-efficiency option. Your contractor can compare the models that fit your venting.
Does a propane furnace work during a power outage?
No, not on its own. The blower, igniter and controls need electricity, so the furnace needs backup power to run. A propane fireplace or vented wall heater that runs without power can keep a room warm in the meantime.
How often should a propane furnace be serviced?
Once a year before the heating season, by a qualified technician. Change or clean the filter on the schedule in your owner's manual.
Will a new furnace change my propane tank size?
It can if the new unit is larger or you are adding appliances. Call us before the swap so we can check your tank and gas line.
Related
Keep reading
Sources: ENERGY STAR: furnaces (opens in a new tab) · Propane Education & Research Council: furnaces and boilers (opens in a new tab) · Placer County Building Services: propane appliances (handout) (opens in a new tab) · U.S. EPA: carbon monoxide and indoor air (includes CPSC alarm and annual appliance inspection advice) (opens in a new tab)
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