Why heat the garage at all
An unheated Edmonton garage in January sits close to outdoor temperatures once the car has cooled down. A heated garage means a car that starts easily, snow that melts off before it reaches the house, and a workshop you can actually use from November to March.
You do not need to keep it at room temperature. Many people hold a garage just above freezing, around 5 C to 10 C, and bump it up when they are working. That keeps water lines and stored liquids safe without heating a big, drafty space all day.
Before choosing a heater, think about how you use the space. A garage that only needs to stay above freezing has very different needs from a woodshop where you work for hours on a Saturday. That use decides the heater size, type and controls.
Types of electric garage heaters
- Hard-wired 240 V unit heaters with a fan are the most common choice. They mount on the ceiling or wall and run from a thermostat.
- Infrared heaters warm people, cars and surfaces directly rather than the air. They recover quickly after the overhead door opens and suit tall or drafty spaces.
- Portable 120 V heaters are for short-term spot heat while you are present. They are not designed to heat a whole garage, and running one for hours on a shared garage circuit is a common cause of tripped breakers and warm cords.
Gas-fired unit heaters are also common in Alberta. They need a gas fitter, venting and a small electrical circuit for the fan and controls.
Sizing the heater
Garage heat loss depends on insulation, ceiling height, the overhead door and how often it opens. A finished, insulated garage with a good door needs far less heat than an uninsulated detached garage with gaps around the door.
Rather than guessing from floor area, a short heat loss estimate gives a better answer. It also shows whether improving the overhead door seals or insulating the ceiling would let you use a smaller heater and a smaller circuit.
Ceiling height matters too. Warm air collects at the top of a tall shop, so a high ceiling may call for a heater with a fan that pushes air down, or infrared heat aimed at the work area.
Weatherstripping the overhead door and insulating the ceiling often cuts the heater size you need. Every bit of heat loss you remove is a smaller circuit and lower running cost.
Wiring and panel capacity
A hard-wired 240 V garage heater needs its own circuit from the panel, sized to the heater's nameplate, plus a line-voltage thermostat or a heater with a built-in thermostat. The heater also needs a way to be disconnected for service.
For an attached garage the circuit often runs from the main panel. A detached garage is usually fed by an underground cable to a subpanel in the garage. If that feed is small, it may not have room for a heater as well as lights, receptacles, a block heater outlet and power tools.
Older homes on 60 A or 100 A services may need a load calculation before adding a large heater. If you are also planning an EV charger, plan both together. They can compete for the same capacity on a cold night.
A new heater circuit or subpanel needs an electrical permit. In Edmonton, that comes from the City of Edmonton. Elsewhere in Alberta it is issued under the Safety Codes Act through your local permit authority.
Placement and clearances
Ceiling unit heaters usually go in a corner, aimed so warm air sweeps across the floor and toward the overhead door, where most cold air comes in. They must be high enough that car hatches, garage door rails and people's heads clear them.
- Keep the heater clear of storage shelves, ladders and anything hanging from the ceiling.
- Keep gasoline, paint, solvents and propane well away from any heater. Fumes and heaters do not mix.
- Follow the manufacturer's mounting heights and clearances exactly.
- Put the thermostat on a side wall out of the heater's direct airflow and away from the overhead door.
Never use a heater with exposed elements near flammable vapours. If you do woodworking, keep sawdust off the heater and clean the intake and fins regularly with the power off.
Garage shops and workshops
If the garage doubles as a workshop, plan heat together with the rest of the wiring: enough receptacles on separate circuits for tools and dust collection, good lighting and a block heater outlet for the car. Doing it all at once avoids running new cable twice.
A thermostat with a setback is handy here: hold the shop just above freezing during the week and warm it up an hour before you start work on the weekend.
Our garage and workshop wiring service can design the whole space, including heater circuits, subpanel and lighting, and handle the permit.
Common questions
Can I run a garage heater off an extension cord?
No. Fixed garage heaters must be hard-wired or plugged into a dedicated receptacle that matches the heater. Extension cords are a common cause of overheating and fires with heaters.
How warm should I keep my garage in winter?
Many people hold it just above freezing and raise it when they are working. The right setting depends on what is stored there and whether water lines run through it.
Does my detached garage need a subpanel for a heater?
Often, yes. A heater plus lights, receptacles and a block heater outlet can exceed a small feed. An electrician can check the existing feed and recommend the right size.
Is infrared better than a fan heater?
Infrared suits garages where the door opens often, because it warms people and surfaces directly. Fan heaters are better at warming the air evenly. Many shops use one of each.
Codes and permit rules change and every building is different. For work on your system, talk to a licensed electrician and your local permit authority.