Electric vs propane garage heater

• The car and the fuel share the bay. An electric heater has no flame. It does not remove the need for clearances, but it removes the open burner.
• You are adding a 240V circuit anyway. A circuit for a heater, a welder or a compressor shares the same work. The 240V outlet install cost calculator prices it from your panel.
• You can insulate the door. Electric heat is exactly as efficient as the building envelope. A reflective door kit such as the NASA TECH two-car kit or the Reach Barrier single-door kit is the best money you can spend with either heater.
• You want to switch it on and walk away. No fuel to run out of, no tank to haul, nothing to vent.

• The bay is large or poorly insulated. 50,000 BTU is twice the output of a 7,500 W electric heater. In a 22 x 22 ft or 24 x 24 ft bay with a bare door, the gas unit gets there faster. The garage heater BTU calculator estimates the need for your bay.
• You have no spare capacity in the panel. A gas unit does not add to your electrical load. If your main panel is full, that matters more than anything else on this page.
• You already have a gas line or a propane tank. Running fuel to an unheated detached garage is a cost; running it to a bay next to a furnace is not.
• Heat-up speed matters. If the garage is cold and you work in short sessions, a fast heater beats a slow one.

It is worth it when you work in the garage in the cold months and the room is insulated enough to hold the heat. It is a waste when the door is a single skin of steel and the walls are bare studs. Heating a leaky garage with any heater is like filling a bath with the plug out. The order is: insulate the door, seal the gaps, then size the heater. The garage heater BTU calculator shows the loss for your bay; every constant on that page is labelled as a convention.

Size is the first question. Electric heat converts watts to BTU at 3.412 BTU per watt, so 7,500 W gives about 25,590 BTU per hour. The Dura Heat unit, at 3,750 W, gives about 12,800, which matches its title. Compare those figures against the loss for your bay. A bay that needs 40,000 BTU per hour at your design temperature does not warm up on a 7,500 W heater. It stays cold at a slightly warmer level.

Our sizing sheets list the circuit and a typical heater for each bay: see the 12 x 22 ft sheet and the 22 x 22 ft sheet.

A 7,500 W heater on 240V pulls 31.3 A. A heater is a continuous load, so the conductor is sized for 125 percent: 39 A. That is a 40 A, double-pole breaker and 8 AWG copper, using the 60 C column of NEC Table 310.16, where 8 AWG is rated 40 A. The InoKraft listing includes a NEMA 14-50P plug, which pairs with a 14-50 receptacle such as the Leviton 1450R. Have a licensed electrician confirm the circuit, the receptacle and the breaker. Do not assume a plug-in unit means a simple install.

The Comfort Zone 7,500 W hard-wired ceiling unit is the same load without a plug: it is wired to the circuit. The smaller Dura Heat 3,750 W unit pulls about 15.6 A at 240V, so 19.5 A at 125 percent, a 20 A, 240V breaker and 12 AWG. Run your own sums in the 240V circuit calculator, and add the heater to the rest of the shop in the workshop amps calculator. A heater and a welder on the same panel can exceed it.

A gas unit changes this. The burner needs no 240V, though a fan needs power. The listing is the place to read the electrical requirement and the gas connection.

It can be, and the conditions are strict. Garages hold gasoline in a tank, in a can for the mower, and in vapors that settle low. Paint, solvents, brake cleaner and finishing products add more. A heater with an open flame or a hot burner in that room is an ignition source, and that is the reason many building codes and manufacturers set clearances and mounting heights for gas appliances in garages. Mr. Heater unit heaters are sold with installation instructions, clearance tables and venting guidance in the manual. Read the listing and the manual, follow local code, and have the gas connection installed by a qualified person.

Combustion also makes carbon monoxide and water vapor. An unvented heater in a closed garage builds both. Check the listing to see whether a unit is vented or ventless, and install a carbon monoxide alarm either way. Water vapor is a rust problem for tools, which is the reason the dehumidifier roundup exists. A combustion heater in a tool-filled shop works against the rust you are trying to prevent.

The portable Mr. Heater Buddy (9,000 BTU radiant) is a different animal. It is a small radiant heater for a work area, not a garage heater, and the same rules about fuel and ventilation apply with more force because it sits on the floor. It is not a pick for a garage with a car or stored fuel; read its listing and manual for the indoor-use rules before you buy.

Fire extinguishers belong in any garage with a heater. The Kidde 2-pack is a standard option.

The electric heater mounts on the ceiling or wall and takes no floor. That matters in a one-car bay. A forced-air gas unit also mounts high, but it needs a fuel line, a vent path in many installations and the clearances in its manual. In a 12 x 22 ft bay, hanging a 50,000 BTU unit is a lot of heater for a small box, and it will cycle on and off. A heater that cycles a lot is oversized.

Car safety adds one more rule: keep the heater clear of the vehicle. A car with a hot engine or exhaust in a bay with an unvented combustion heater adds more hazards, and a car with a fuel leak next to a pilot or a burner is a bad day. Electric elements get hot too; the heater needs clearance from the car's roof and the door in motion. If the unit hangs above the parking spot, check that a tall truck or a roof rack does not reach it.

Our bay sheets are the place to start: 12 x 22 ft auto layout and 22 x 22 ft mixed layout.

Electric resistance heat turns every watt into heat, so the cost is your kWh rate times the kWh. Propane or natural gas cost depends on your fuel price and the unit's efficiency, and we do not type a price here. The comparison depends on two local prices and on how many hours you run. Do it with your own numbers: BTU needed per hour, divided by 3.412 for watts of electric heat, times your kWh price; or BTU divided by the gas unit's efficiency and your fuel price per BTU.

A heat pump beats both on running cost. A mini-split moves heat instead of making it, which is why the next page, mini-split against electric heater, exists. If you run the heater all winter, the mini-split's higher entry price is repaid by lower running cost.

Electric for a garage with a car, fuel and finishes; propane or gas for a big, leaky bay where the panel is full. If you will insulate the door and can give the heater a 40 A, 240V circuit, the 7,500 W electric unit is the safer heater for a shop that shares its air with a car. If you cannot add a circuit and the bay is large, the gas unit is the practical heater, installed to code, with a CO alarm and a clear zone around it. The garage heater roundup has the full list.