Most two-car garages need a 30,000 to 45,000 BTU heater, or about 8 to 13 kW electric. Enter your garage size, insulation and climate below to find the right size and compare what each type of heater costs to install and run.
Garage Heater Size and Cost Calculator
1Garage size
2How you’ll heat it
3Energy prices and region
Installed cost
| Item | Cost |
|---|---|
| Total installed | $0 |
Compare heater types
| Heater | Installed | Per month | 5 years |
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What Size Heater Do I Need for My Garage?
Most two-car garages need a 30,000 to 45,000 BTU heater, or about 8 to 13 kW if it’s electric. A one-car garage needs about 15,000 to 20,000 BTU, and a three-car garage 45,000 to 65,000 BTU. The right size depends on the garage’s volume, how well it’s insulated, how cold it gets outside and how warm you want it inside.
| Garage | Not insulated | Partly insulated | Fully insulated | Spray foam |
|---|---|---|---|---|
| 1-car (12 x 22, 9 ft ceiling) | 20,000 BTU | 20,000 BTU | 15,000 BTU | 10,000 BTU |
| 2-car (24 x 24, 9 ft ceiling) | 45,000 BTU | 35,000 BTU | 30,000 BTU | 25,000 BTU |
| 3-car (36 x 24, 9 ft ceiling) | 65,000 BTU | 50,000 BTU | 45,000 BTU | 35,000 BTU |
| 30 x 40 shop (12 ft ceiling) | 120,000 BTU | 95,000 BTU | 80,000 BTU | 60,000 BTU |
How Garage Heater Sizing Works
Garage heater sizing uses a simple rule: BTU = cubic feet x temperature rise x insulation factor. The temperature rise is the difference between the temperature you want and the coldest typical outdoor temperature where you live. The insulation factor ranges from about 0.1 for a spray-foamed garage to 0.2 for an uninsulated one. To convert to an electric heater, divide the BTUs by 3,412 to get kilowatts.
| Climate (2-car garage, 55°F) | Not insulated | Partly insulated | Fully insulated |
|---|---|---|---|
| Warm (South, Southwest) | 30,000 BTU | 25,000 BTU | 20,000 BTU |
| Mixed (Mid-Atlantic, lower Midwest) | 45,000 BTU | 35,000 BTU | 30,000 BTU |
| Cold (Northeast, upper Midwest) | 60,000 BTU | 50,000 BTU | 40,000 BTU |
| Very cold (northern plains, mountains) | 75,000 BTU | 60,000 BTU | 50,000 BTU |
Garage Heater Cost: Purchase, Installation and Operating Costs
| Heater (2-car garage, 35,000 BTU) | Installed cost | Per month, 10 hrs/week | Per month, heated all winter |
|---|---|---|---|
| 240V electric unit heater (10 kW) | About $1,430 | About $23 | About $190 |
| Propane vented unit heater | About $2,820 | About $16 | About $135 |
| Natural gas vented unit heater | About $2,620 | About $7 | About $60 |
| Gas infrared tube heater | About $3,525 | About $7 | About $58 |
| Ductless mini-split heat pump | About $5,940 | About $9 | About $77 |
240V Electric Heaters
Electric unit heaters are the cheapest to buy and install, need no venting or gas line, and are safe and quiet. They’re the best choice if you only heat the garage a few hours a week. Shop 240V garage heaters here. They cost the most to run, though, and a heater over about 10 kW may need a bigger circuit or a subpanel. Small 120V plug-in heaters (1.5 kW, about 5,100 BTU) can take the chill off a one-car garage but won’t heat a two-car garage in winter.
Propane and Natural Gas Heaters
Vented gas unit heaters hang from the ceiling and heat a garage quickly. Natural gas is the cheapest fuel to run in most areas if you already have service at the house. Propane costs more to run but works anywhere. Always choose a vented model for an enclosed garage. Unvented “ventless” propane and kerosene heaters release carbon monoxide and a lot of moisture.
Infrared Tube Heaters
Infrared heaters warm people, tools and the floor rather than the air, so they work well in tall shops and garages where the door opens often. They need about 10 feet or more of ceiling height for safe clearance.
Ductless Mini-Splits
A mini-split heat pump costs the most to install, about $4,000 to $6,500 for a two-car garage, but it’s two to three times more efficient than an electric heater and also cools the garage in summer. It’s the best choice for a garage gym, office or finished space. In very cold climates, choose a cold-climate (hyper-heat) model.
Get Quotes from Local Heating Pros
Ask HVAC contractors to confirm the heater size for your garage and include the gas line or electrical circuit, venting, thermostat and permit in the quote.
Ways to Lower Garage Heating Costs
- Insulate first. Insulating an uninsulated two-car garage can drop the heater size from about 45,000 to 30,000 BTU and cut running costs by about a third. Price it with our garage insulation cost calculator.
- Seal the garage door. A new bottom seal and weatherstripping stop the biggest drafts for about $150.
- Use a thermostat. Keep the garage at 40°F to protect against freezing, then turn it up only when you’re working.
- Don’t oversize. A heater that’s far too big cycles on and off, wasting fuel and making the space less comfortable.
Turning the garage into a gym, office or living space? See our garage conversion cost calculator, and for summer comfort, our guide on how to keep your garage cool in summer.
Frequently Asked Questions
How many BTUs do I need to heat a 2-car garage?
About 30,000 to 45,000 BTU for a typical 24 x 24 garage with a 9-foot ceiling, depending on insulation and climate. An insulated garage in a mild climate may need only 20,000 to 25,000 BTU, while an uninsulated garage in a cold climate may need 60,000 BTU or more.
What size electric heater do I need for a garage?
Divide the BTUs you need by 3,412. Most two-car garages need an 8 to 13 kW, 240V heater. A one-car garage usually needs 4 to 6 kW. Once you know your size, you can compare garage heaters online.
What is the cheapest way to heat a garage?
For occasional use, a 240V electric heater is cheapest overall because it costs the least to install. For a garage heated all winter, natural gas or a mini-split heat pump is usually cheapest to run.
How much does it cost to heat a garage per month?
Heating a partly insulated two-car garage for about 10 hours a week costs roughly $7 to $25 a month. Keeping it at 50°F all winter costs about $60 a month with natural gas and up to about $190 with an electric heater, depending on your energy prices and climate.
Is it safe to use a propane heater in a garage?
Only a vented propane heater installed to code should be used in a closed garage. Portable unvented heaters release carbon monoxide and should only be used with plenty of ventilation. Install a carbon monoxide detector in any heated garage.
Pricing last updated October 2026 using national-average equipment and installation costs and 2026 average energy prices. Sizing is an estimate; have a heating contractor confirm the size for your garage.
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