240V or 120V: work this out before you shop
Everything in this category follows from one number — the circuit you have or are willing to install.
- 120V, 15-amp (an ordinary socket): about 1,500 watts maximum, roughly 5,100 BTU. Heats one bay, one bench, one person. No electrician needed.
- 240V, 20-30 amp (a new circuit): 3,000 to 7,500 watts, roughly 10,000 to 25,500 BTU. Heats a one or two-car garage properly. Needs an electrician and a spare breaker space.
The 220V and 240V labels on these listings mean the same thing in practice — a residential US two-pole circuit, nominally 240 volts. Do not read anything into the difference.
How much heater does a garage need?
A rough, honest method: for an uninsulated attached garage in a cold climate, budget around 7 to 10 watts per square foot to hold a working temperature; for an insulated one, 4 to 6. A 400 square foot single garage, insulated, lands around 2,000 watts — the DR-966 on its low setting. A 600 square foot double, uninsulated, wants 4,500 to 6,000, which is the DR-966 on high or the Fahrenheat.
None of these listings publishes a heated area in square feet except the NewAir, which states 160. That is why we have flagged “not published” on the rest rather than inventing figures. Insulation changes the answer more than any heater does: insulating the garage door is the cheapest watt you will ever buy.
A thermostat is the feature that pays for itself
A heater with no thermostat is a switch: full output until you remember to turn it off. A heater with one cycles to hold a set temperature and spends most of a mild day doing nothing. Over a winter at 6,000 watts, the difference is real money — which is the whole argument for the DR-975 and the FLCH4R over a cheaper unit, and the reason a “best electric garage heater with thermostat” search is a sensible one.
Two practical notes. Mount the heater high and aim it across the space rather than at a wall. And if the garage is where you work on a car, keep the heater well clear of where fuel vapor can pool — an electric element is an ignition source like any other.
Electric or propane for a garage?
Electric has no combustion, so no carbon monoxide, no ventilation requirement and no cylinder to refill. It is the safer choice for a space you spend hours in with the door shut. The cost is the circuit and the running cost per BTU, which is higher than propane almost everywhere.
Propaneis faster and cheaper per BTU, and it needs ventilation — which is workable in a garage because you can open the door, and is exactly why we treat garages differently from living rooms. If that trade suits you, see propane garage heaters for the forced-air and vent-free options, and is a propane heater safe indoors for the ventilation rules.
For a covered porch or a patio rather than a garage, the answer is a different shape of heater entirely — electric porch heaters are weather-rated infrared bars that warm people rather than air, and propane vs electric patio heater works through that comparison properly.
If you have firewood rather than a spare circuit
Wood is the cheapest garage heat to run by a wide margin and the most expensive to install, because it needs a code-compliant chimney rather than a cable. Best wood stove for a garage ranks that route — and leads with the one disqualifier electric does not have: a garage that stores gasoline, solvent or aerosols is the wrong room for any solid-fuel appliance, because those vapors collect at exactly the floor level a stove draws its air from.
