Infrared Garage Heater Sizing
Heat the bench, not the whole garage. Draw your work area, pick a mounting height, and see which infrared heater covers it, how its beam lands on the floor and what it costs an hour.
Your garage
Spot heat for your work area
One 2.5 kW heater
Warming 80 sq ft by 20°F takes about 1,600 W of infrared (20 W per sq ft). Heating the whole garage to 60°F instead would take about 12,200 W of forced air.
How much floor one heater covers
The floor pattern and the heat it puts on the floor both change with mounting height. These are Detroit Radiant's published figures for its BAH electric infrared heaters; other heaters differ, so check your model's chart.
| Mounted at | 1,750 W | 2,500 W | 3,000 W | 4,000 W |
|---|---|---|---|---|
| 8 ft | 9.5 × 12 ft · 16.1 W/ft² | 9.5 × 13 ft · 20.1 W/ft² | 9.5 × 14.5 ft · 22 W/ft² | 9.5 × 14.5 ft · 29.4 W/ft² |
| 9 ft | 10.5 × 13 ft · 13.4 W/ft² | 10.5 × 14 ft · 16.8 W/ft² | 10.5 × 15.5 ft · 18.6 W/ft² | 10.5 × 15.5 ft · 24.9 W/ft² |
| 10 ft | 11.5 × 14.5 ft · 11.1 W/ft² | 11.5 × 15.5 ft · 14.5 W/ft² | 11.5 × 16.5 ft · 16 W/ft² | 11.5 × 16.5 ft · 21.6 W/ft² |
| 12 ft | — | 14 × 18 ft · 10 W/ft² | 14 × 19 ft · 11.2 W/ft² | 14 × 19 ft · 15 W/ft² |
How the calculator sizes infrared
One work area. Fostoria's indoor spot-heating rule is the area times the temperature rise you want above the garage air: an 8 × 10 ft bench zone warmed 20°F needs about 1,600 W, or 20 W per square foot. We then pick the smallest heater whose floor pattern covers the zone and delivers that density at your mounting height. When one heater cannot, we cross two beams over the zone, as Fostoria advises; with the garage air at 30°F that becomes 2 × 1,750 W.
The whole garage. Detroit Radiant's chart asks for 10 W per square foot in an insulated building and 16 W uninsulated at a 0°F design, plus 0.75 W per 5°F below zero, adjusted 10% per foot of mounting height away from 9 ft. For an insulated 24 × 24 garage at 8 ft that is about 5,200 W. Fostoria's simpler whole-area rule ignores insulation, so it reads higher; the calculator shows both.
Infrared needs fewer watts than forced air for the same comfort because it warms people and surfaces rather than the air. Our garage heater calculator sizes forced-air heat for the same garage at about 12,200 W.
Placing the heaters
- Mount at 8 ft or higher, and not directly over where someone stands or lies.
- Cross two beams over a work area so you are warmed from both sides.
- For whole-garage heat, aim heaters along the outside walls and the garage door, where heat escapes.
- Keep the clearances in the heater's manual to cars, shelves and anything that can burn.
Questions people ask
What size infrared heater do I need for a garage?
For one 8 × 10 ft work area, warming you 20°F above the garage air takes about 1,600 W; one 2,500 W heater mounted at 8 ft covers it. Heating a whole insulated 24 × 24 garage takes about 5,200 W of infrared at a 0°F design low, from Detroit Radiant's application chart.
Is infrared better than a forced-air garage heater?
For one work area, usually: infrared warms you and the bench directly, so the air can stay cold. Our default work area costs about $0.43 an hour, against about $1.06 an hour for a forced-air heater keeping the whole garage at 60°F. For holding the whole garage at temperature, a vented gas unit heater is usually cheaper to run.
How high should an infrared garage heater be mounted?
Fostoria's sizing sheet says not to mount below 8 ft and not directly over someone's head. Higher mounting spreads the heat over more floor but lowers the watts per square foot, which is why Detroit Radiant adds 10% of the total watts for each foot above 9 ft.
Why does the floor stay cold under forced air but not under infrared?
Infrared heats surfaces it reaches, including the slab, tools and you. Forced air has to warm the air first, and warm air sits at the ceiling while the concrete keeps soaking up heat. See how long the slab takes to warm.
What circuit does an electric infrared heater need?
A 240 V heater draws its watts divided by 240: about 10.4 A for 2,500 W and 16.7 A for 4,000 W. Fixed heating circuits are sized at 125% of the load, and the heater's manual and your electrician set the breaker and wire. Use the wire size calculator.
Sources
Sources last checked November 7, 2026.
- Detroit Radiant Products, Re-Verber-Ray BAH electric infrared application chart (accessed November 7, 2026) · heat patterns, floor watt density, 10/16 W per sq ft at 0°F, mounting-height adjustment
- Liberty Electric Products, Electric infrared sizing information (Fostoria) (accessed November 7, 2026) · whole area ft² × 0.5 × rise; spot ft² × 1 × rise; do not mount below 8 ft