A cold garage is a solvable problem — but the wrong heater either trips your breaker, costs a fortune to run, or quietly fills the room with carbon monoxide. This guide walks through the three decisions that actually matter: how big a heater you need, which fuel type fits your space, and how to install it safely. No jargon, no padding.
What's in this guide
1. Sizing: how big?
Get this right and everything else is easy. Size a heater too small and it runs constantly without ever warming the room; too big and you've overspent and may overload your circuit. Two quick rules of thumb for a moderately insulated garage:
- Electric heaters: about 10 watts per square foot.
- Combustion heaters (propane/gas): about 34 BTU per square foot.
If your garage is uninsulated, in a cold climate, or has high ceilings, add 25–50%. Here's the math done for common sizes:
| Garage | Approx. size | Electric (watts) | Propane (BTU) |
|---|---|---|---|
| 1-car | ~250 sq ft | 2,500 W | ~9,000 BTU |
| 2-car | ~450 sq ft | 4,500 W | ~17,000 BTU |
| 3-car | ~650 sq ft | 6,500 W | ~24,000 BTU |
| Large shop | 1,000+ sq ft | 10,000 W+ | 40,000 BTU+ |
2. The four heater types
Almost every garage heater falls into one of these buckets. Each has a clear best-use case.
Electric — fan-forced
A heating element with a fan blowing warm air. Clean, no fumes, no ventilation needed, safe to leave running. The trade-off is electricity cost and that bigger units need 240V wiring. Best for: attached garages, anyone who wants set-and-forget heat without combustion risk.
Electric — infrared / radiant
Heats objects and people directly rather than the air, like standing in sunlight. It warms you almost instantly even in a drafty space, and the heat doesn't vanish the second a door opens. Best for: workshops where you're working in one spot, or poorly sealed garages where heating the air is a losing battle.
Propane — forced-air
High heat output for the money, fully portable, no wiring. But it burns fuel indoors, which means it produces moisture and combustion byproducts and requires ventilation. Best for: big or detached shops, intermittent use, spaces without the electrical capacity for a large electric unit.
Natural gas
If you have a gas line, a permanently mounted gas unit heater is the cheapest to run for a large space. Higher install cost and usually a job for a pro. Best for: large garages and shops in regular year-round use.
3. Electric: 120V vs 240V
This catches people out. A standard wall outlet is 120V and tops out around 1,500 watts — enough for a small, well-insulated single bay, not much more. To meaningfully heat a two-car garage with electricity you'll want a 240V unit, which needs a dedicated circuit (the kind a dryer or welder uses).
- 120V plug-in (≤1,500W): plugs into a normal outlet, zero install. Small spaces only.
- 240V hardwired (3,000–10,000W+): needs a dedicated circuit, often a licensed electrician. Real garage heat.
If running a 240V circuit isn't realistic, that's often the deciding reason people go propane instead.
4. Safety (don't skip)
- Keep at least 3 feet of clearance from anything flammable — and garages are full of gasoline, paint, and solvents. Vapors are heavier than air and pool near the floor; mount heaters high.
- Choose units with tip-over shutoff and overheat protection.
- Don't run a space heater on an extension cord — plug 120V units straight into the wall.
- Match the heater to the circuit; a unit that trips your breaker is undersized wiring, not a faulty heater.
5. Our top picks
We keep our current recommendations — sorted by garage size and fuel type — on the homepage, updated as models change and prices move.
Updated for 2026 View our top garage heater picks → Best overall · best budget · best for big shopsFrequently asked questions
- What size heater for a 2-car garage?
- For a moderately insulated two-car garage (~450 sq ft), aim for roughly 4,500 watts of electric heat or about 17,000 BTU of propane. Add 25–50% if it's uninsulated or in a cold climate.
- Are electric or propane garage heaters cheaper to run?
- It depends on local electricity and propane prices, but propane usually delivers more heat per dollar for large spaces, while electric wins on convenience and zero ventilation needs. Natural gas, if available, is typically the cheapest of all to run.
- Can I use a regular space heater in my garage?
- A 120V space heater works for a small, well-sealed single bay but won't keep up with a larger or drafty garage, and many household models aren't rated for the dust and temperature swings of a garage.
- Do I need a special outlet?
- For anything above 1,500 watts, yes — you'll need a dedicated 240V circuit, which usually means hiring an electrician. Below that, a standard outlet is fine.
Found this useful? The homepage has our current top picks for each garage size and fuel type, with prices kept up to date.