Size a garage heater from three things: the garage's volume, how much warmer than outside you want it, and how well it is insulated. Our calculator multiplies cubic feet by the temperature rise by a heat-loss factor of 0.17 with no insulation, 0.12 with insulated walls only and 0.05 with walls, ceiling and door insulated. A 24 x 24 ft two-car garage with a 9 ft ceiling, heated from 0 F to 50 F, needs about 13,000 BTU an hour fully insulated, 31,200 with walls only and 44,100 with no insulation.
Our picks at a glance
From published specs and our sizing rules. Not lab tested.
- 1
Insulated 2-car garage
Comfort Zone CZ220BK 5,000 W Ceiling Mount Garage Heater
17,060 BTU, 240V hardwired
Check price on AmazonPaid link
- 2
Walls-only insulation, 2-car
Comfort Zone CZ260ER 10,000 W Ceiling Garage Heater with Remote
34,120 BTU, 240V hardwired
Check price on AmazonPaid link
- 3
Big or uninsulated shops
Mr. Heater Big Maxx 80,000 BTU Vented Garage Unit Heater
80,000 BTU input, vented LP or NG
Check price on AmazonPaid link
- 4
Bench heat from any outlet
Lasko Elite Collection Ceramic Utility Heater CU12510
1,500 watts, 120V plug-in
Check price at LaskoPaid link
That number picks the fuel. A 120V plug-in heater tops out at 1,500 W, or 5,118 BTU, which is spot heat at the bench in most garages. A 240V heater runs 3,750 to 10,000 W (12,800 to 34,120 BTU) on its own circuit. Past that, vented propane or natural gas unit heaters deliver 36,000 to 64,000 BTU.
The short answer: a 5,000 W 240V ceiling heater for an insulated two-car garage, a 10,000 W unit if only the walls are insulated, and a vented 80,000 BTU gas unit heater for a large uninsulated shop. If you only want to stay warm at the workbench, a 1,500 W plug-in is enough.
Top picks, and why
Comfort Zone CZ220BK 5,000 W Ceiling Mount Garage Heater
- 240V
- electric
- 5,000 W
- Hardwired 240V
+2 moreFewer
- Ceiling mount
- Thermostat
5,000 W (17,060 BTU) hardwired 240V ceiling heater with a knob thermostat and adjustable louvers. Covers the 13,000 BTU a fully insulated 2-car garage needs at 0 F. under $100.
- Ceiling mount keeps the floor clear
- Knob thermostat, adjustable louvers and mounting angle
- Thermal cut-out, heavy gauge steel, ETL
- Hardwired: needs a 240V circuit run by an electrician
- Knob controls, no remote
Under $100, live price on Amazon
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Comfort Zone CZ260ER 10,000 W Ceiling Garage Heater with Remote
- 240V
- electric
- 10,000 W
- Remote
+2 moreFewer
- Digital thermostat
- 12 h timer
10,000 W (34,120 BTU) 240V ceiling heater with a digital thermostat, remote and 12 hour timer. Covers the 31,200 BTU of a 2-car garage with only the walls insulated. Needs a 60 A circuit. $100 to $250.
- Digital thermostat, full-function remote, 12 hour timer
- Fully sheathed elements, enclosed motor for dusty shops
- Adjustable ceiling bracket
- Needs a 60 amp 240V circuit
$100 to $250, live price on Amazon
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Mr. Heater Big Maxx 80,000 BTU Vented Garage Unit Heater
- gas
- 2,667 sq ft
- Vented
- Propane or natural gas
+2 moreFewer
- 24V thermostat
- 10 ft min ceiling
80,000 BTU vented unit heater for propane or natural gas, about 64,000 BTU delivered at 80 percent. Exhaust goes outside through a flue. Needs a 10 ft ceiling. $500 to $1,000.
- Vented: combustion gases go outside
- Propane or natural gas
- Works with a standard 24V thermostat (sold separately)
- Needs a 10 ft ceiling and 8 ft clearance under the heater
- Gas line, flue and thermostat wiring: plan on a pro install
$500 to $1,000, live price on Amazon
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Lasko Elite Collection Ceramic Utility Heater CU12510
- 120V
- electric
- 120V plug-in
- Digital thermostat
+2 moreFewer
- 8 h timer
- Tip-over switch
1,500 W ceramic utility heater with a digital thermostat, 8 hour timer and tip-over switch. Plugs into a standard outlet; about $0.26 an hour at the US average rate. about $40.
- Adjustable digital thermostat, 2 heat settings
- Up to 8 hour auto-off timer
- Overheat protection, tip-over switch, cool-touch exterior
- 1,500 W (5,118 BTU) is the most a 120V outlet can deliver
About $40 at Lasko, checked Oct 24, 2026
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Compare every pick
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How much heat your garage needs
Heated from 0 F to 50 F (a Chicago, Denver or Boston design night) with a 9 ft ceiling: a 1-car garage (288 sq ft) needs about 6,500 BTU fully insulated, 15,600 with walls only and 22,100 with no insulation. A 2-car (576 sq ft) needs 13,000, 31,200 and 44,100. A 3-car (864 sq ft) needs 19,500, 46,700 and 66,100.
In a milder climate scale by the temperature rise. In an Atlanta-like zone with a 22 F design low, the rise is 28 F instead of 50 F, so a fully insulated 1-car garage needs about 3,700 BTU and a 2-car with walls only needs about 17,500.
Insulation is the cheapest upgrade. Adding ceiling and door insulation to a 2-car garage with insulated walls cuts the need from 31,200 to 13,000 BTU, which turns a 10,000 W heater on a 60 A circuit into a 5,000 W heater on a 30 A circuit.
Comfort Zone CZ230ER 7,500 W Ceiling Garage Heater with Remote
- 240V
- electric
- 1,250 sq ft
- 7,500 W
+3 moreFewer
- Remote
- Digital thermostat
- 12 h timer
7,500 W (25,590 BTU) 240V ceiling heater with a digital thermostat, remote and 12 hour timer, rated for up to 1,250 sq ft. Covers a fully insulated 3-car garage at 0 F (19,500 BTU). Needs a 40 A circuit. $100 to $250.
- Digital thermostat with remote and 12 hour timer
- Rated for up to 1,250 sq ft
- Ceiling mount, overheat shut-off, steel body
- Hardwired: needs a 40 amp 240V circuit
$100 to $250, live price on Amazon
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120V plug-in heaters: spot heat
1,500 W is the most a standard 120V outlet allows, which makes 5,118 BTU an hour. That is enough to heat a fully insulated 1-car garage in a mild climate (3,700 BTU in the Atlanta example), but in a 2-car or uninsulated garage it warms you at the bench rather than the space.
At the 17.3 cent US average, 1,500 W costs about $0.26 an hour. Point it at where you stand and use the thermostat so it cycles off once the area is warm.
Lasko Elite Collection Ceramic Utility Heater CU12510
- 120V
- electric
- 120V plug-in
- Digital thermostat
+2 moreFewer
- 8 h timer
- Tip-over switch
Digital thermostat, 2 heat settings, up to 8 hour auto-off timer, overheat protection and tip-over switch. about $40.
- Adjustable digital thermostat, 2 heat settings
- Up to 8 hour auto-off timer
- Overheat protection, tip-over switch, cool-touch exterior
- 1,500 W (5,118 BTU) is the most a 120V outlet can deliver
About $40 at Lasko, checked Oct 24, 2026
Check price at LaskoPaid link. We earn a commission at no cost to you.
NewAir NGH160GA00 120V Portable Garage Heater
- 120V
- electric
- 120V plug-in
- Metal housing
+2 moreFewer
- Tilting head
- 160 sq ft rating
1,500 W ceramic heater in a metal housing with a tilting head to aim the heat, 2 heat settings and adjustable temperature control, ETL certified. NewAir rates it for 160 sq ft. under $100.
- Metal housing, tilting head to aim the heat
- 2 heat settings and adjustable temperature control
- Cool-touch exterior and automatic shut-off, ETL certified
- NewAir rates it for 160 sq ft, so it is spot heat in a 2-car garage
Under $100, live price on Amazon
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Dr. Infrared Heater DR218 1,500 W Garage and Workshop Heater
- 120V
- electric
- 120V plug-in
- IPX4
+1 moreFewer
- 150 sq ft rating
IPX4 splash protection for damp garages, greenhouses and workshops, rated for 150 sq ft. One heat setting. $100 to $250.
- IPX4 splash protection for damp garages
- Light and portable, plugs into a standard outlet
- One heat setting; the listing names no thermostat
- Rated for 150 sq ft
$100 to $250, live price on Amazon
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240V electric: sizes, circuits and cost per hour
Fixed electric heat is a continuous load, so the NEC sizes the circuit at 125 percent of the heater's amps. 4,800 to 5,000 W draws about 20 A and needs a 30 A double-pole breaker on 10 AWG copper. 7,500 W draws 31.3 A: a 40 A breaker and 8 AWG. 10,000 W draws 41.7 A: a 60 A breaker and 6 AWG. Plug-in 240V heaters go on the circuit their plug is rated for.
Match the heater to the need: up to 17,060 BTU a 5,000 W unit, up to 25,590 BTU a 7,500 W unit, up to 34,120 BTU a 10,000 W unit. Past that, two heaters on two circuits or a vented gas heater. At the 17.3 cent US average, full heat costs about $0.65 an hour at 3,750 W, $0.86 at 5,000 W, $1.30 at 7,500 W and $1.73 at 10,000 W; the thermostat cuts that once the garage is warm.
Electric heaters cost the least to buy and install if you already have 240V in the garage, and they put nothing into the air.
Dura Heat EUH4000 240V Garage Heater, 6-20P Plug
- 240V
- electric
- 3,750 W
- NEMA 6-20P plug
+2 moreFewer
- Thermostat
- 500 sq ft rating
3,750 W (12,800 BTU) on a NEMA 6-20P plug, so it needs a 20 A 240V outlet but no hardwiring. Thermostat, wall or ceiling mount, rated for 500 sq ft. $100 to $250.
- Plugs into a 20 amp 240V outlet (NEMA 6-20)
- Thermostat and overheat shut-off
- Wall or ceiling mount, steel body
- Needs a 240V outlet, not a regular 120V one
$100 to $250, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Mr. Heater 4,800 W 240V Garage Utility Heater (plug-in)
- 240V
- electric
- 4,800 W
- 30 A 240V plug
+2 moreFewer
- Thermostat
- Wall or ceiling
4,800 W (16,400 BTU) with a 71 inch cord and grounded plug for a 30 A 240V outlet. Adjustable thermostat, wall or ceiling bracket. $100 to $250.
- 71 inch cord with grounded 240V plug
- Adjustable thermostat, overheat protection
- Bracket mounts on a wall or ceiling
- Needs a 30 amp 240V outlet
- One heat setting
$100 to $250, live price on Amazon
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Dr. Infrared Heater DR-975 7,500 W Hardwired Garage Heater
- 240V
- electric
- 4,700 / 7,500 W
- Remote thermostat
+2 moreFewer
- Wall or ceiling
- UL listed
4,700 W or 7,500 W with a remote thermostat (50 to 85 F) and timer, UL/cUL listed. The maker specifies 8 AWG copper. $100 to $250.
- Two outputs: 4,700 W or 7,500 W
- Remote thermostat (50 to 85 F) and timer
- UL/cUL listed, fully enclosed motor
- Hardwired, no cord included; 8 AWG wire per the maker
$100 to $250, live price on Amazon
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NewAir 10,000 W Hardwired 240V Garage Heater
- 240V
- electric
- 7,500 / 10,000 W
- Remote
+2 moreFewer
- Digital thermostat
- 1,605 sq ft rating
7,500 W or 10,000 W settings with a digital thermostat and remote, rated for up to 1,605 sq ft. Ceiling, wall or countertop mount, needs a 60 A circuit. $250 to $500.
- 7,500 W or 10,000 W settings with digital thermostat
- Stainless steel element, coated steel housing, ETL
- Ceiling, wall or countertop mounting
- Hardwired: needs a 60 amp 240V circuit
$250 to $500, live price on Amazon
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King KB ECO2S 7,500 W Garage Heater
- 240V
- electric
- 7,500 W
- Thermostat + remote
+2 moreFewer
- Fan delay
- Fan-only mode
King's 7,500 W heater with thermostat, remote, fan delay, summer fan-only mode and a universal wall or ceiling bracket. Needs a 40 A circuit. $1,000 to $2,000.
- Built-in fan delay clears heat after shut-off
- Summer fan-only and timer modes
- Remote and universal wall/ceiling bracket included
- Several times the price of other 7,500 W heaters
- Hardwired: needs a 40 amp 240V circuit
$1,000 to $2,000, live price on Amazon
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Vent-free propane and natural gas
A vent-free heater puts all of its heat into the garage, but also its carbon monoxide, CO2 and water vapor. The makers require fresh air while one runs, so crack a window or the door, and keep a CO alarm in the garage plus one inside by the door if the garage is attached. Gas codes (NFPA 54 and the International Fuel Gas Code) want the burner at least 18 inches above the floor, away from gasoline vapor.
Our calculator applies the NFPA 54 unconfined-space test: at least 50 cu ft of garage per 1,000 BTU of input. An 18,000 BTU heater needs 900 cu ft and a 30,000 BTU heater needs 1,500 cu ft, so both pass in a 1-car garage with a 9 ft ceiling (2,592 cu ft).
At $2.75 a gallon, propane costs about $0.54 an hour at 18,000 BTU and $0.90 at 30,000 BTU. Natural gas at $1.50 a therm runs the 30,000 BTU wall heater for about $0.45 an hour.
Mr. Heater Big Buddy PRO 18,000 BTU Propane Heater
- propane
- 4k / 9k / 18k BTU
- Portable
- Radiant + fan
+1 moreFewer
- 450 sq ft rating
4,000, 9,000 and 18,000 BTU settings, radiant heat plus a fan, rated for 450 sq ft. Runs on 1 lb cylinders or a 20 lb tank with a hose. $100 to $250.
- Three settings: 4,000 / 9,000 / 18,000 BTU
- Radiant heat plus a built-in fan
- No wiring: 1 lb cylinders or a 20 lb tank with a hose
- Unvented: combustion gases and moisture stay in the garage
- Rated for 450 sq ft
$100 to $250, live price on Amazon
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Mr. Heater 30,000 BTU Vent Free Blue Flame Dual Fuel Heater
- gas
- 1,000 sq ft
- Propane or natural gas
- Thermostat
+2 moreFewer
- Low-oxygen shut-off
- No electricity
30,000 BTU convection heater for propane or natural gas with a built-in thermostat, battery spark ignition and low-oxygen shut-off, rated for 1,000 sq ft. No electricity needed. Covers a 1-car garage with walls only insulated at 0 F (15,600 BTU) or a 2-car in a 12 F zone with walls insulated (23,700). $100 to $250.
- Propane or natural gas
- Built-in thermostat, battery spark ignition, no electricity
- Low-oxygen safety shut-off
- Unvented: needs fresh air and a CO alarm
- Needs a gas line run to the wall; blower kit sold separately
$100 to $250, live price on Amazon
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Mr. Heater 30,000 BTU Vent Free Radiant Propane Heater
- propane
- 1,000 sq ft
- Radiant
- Thermostat
+2 moreFewer
- Low-oxygen shut-off
- No electricity
30,000 BTU infrared plaque heater for propane, rated for 1,000 sq ft. Radiant heat warms you and the floor, so you still feel it when the door opens. Restricted to 4,500 ft altitude. $250 to $500.
- Radiant heat you feel even when the door opens
- Built-in thermostat, battery ignition, no electricity
- Low-oxygen safety shut-off
- Unvented: needs fresh air and a CO alarm
- Propane only; the maker restricts it to 4,500 ft altitude
$250 to $500, live price on Amazon
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Kidde Carbon Monoxide + Natural Gas and Propane Alarm
One plug-in alarm for carbon monoxide and for natural gas or propane leaks, with a digital display and 9V battery backup. under $100.
- Detects CO plus natural gas and propane leaks
- Digital display shows CO level or GAS
- Plugs into a 120V outlet, 9V battery backup
- Needs an outlet near the heater
Under $100, live price on Amazon
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Vented gas unit heaters: large or uninsulated garages
A vented unit heater sends its exhaust outside through a flue, so nothing stays in the garage air. About 80 percent of the fuel ends up as heat: the 50,000 BTU Big Maxx delivers about 40,000 BTU, the 80,000 BTU Big Maxx about 64,000 and the 45,000 BTU Modine about 36,000.
That is the range an uninsulated 2-car garage in a cold zone needs (44,100 BTU at 0 F), which no vent-free or single electric heater we list covers. The Big Maxx needs a 10 ft ceiling and 8 ft of clearance under it, and ships without a thermostat. Plan on a pro for the gas line, flue and thermostat wiring.
Natural gas is the cheapest heat per hour in most states. Vented, it costs about $1.88 per 100,000 BTU of heat at $1.50 a therm, against $3.76 for vented propane at $2.75 a gallon and $5.07 for electric at 17.3 cents a kWh. The 80,000 BTU Big Maxx on full fire costs about $1.20 an hour on natural gas and $2.40 on propane.
Mr. Heater Big Maxx 50,000 BTU Vented Garage Unit Heater
- gas
- 1,667 sq ft
- Vented
- Propane or natural gas
+2 moreFewer
- 24V thermostat
- 10 ft min ceiling
50,000 BTU input, propane or natural gas, rated for about 1,667 sq ft, works with a standard 24V thermostat. $250 to $500.
- Vented: combustion gases go outside
- Propane or natural gas
- Works with a standard 24V thermostat (sold separately)
- Needs a 10 ft ceiling and 8 ft clearance under the heater
- Gas line, flue and thermostat wiring: plan on a pro install
$250 to $500, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Mr. Heater Big Maxx 80,000 BTU Vented Garage Unit Heater
- gas
- 2,667 sq ft
- Vented
- Propane or natural gas
+2 moreFewer
- 24V thermostat
- 10 ft min ceiling
80,000 BTU input, propane or natural gas, rated for about 2,667 sq ft. Covers an uninsulated 2-car garage at 0 F with room to spare. $500 to $1,000.
- Vented: combustion gases go outside
- Propane or natural gas
- Works with a standard 24V thermostat (sold separately)
- Needs a 10 ft ceiling and 8 ft clearance under the heater
- Gas line, flue and thermostat wiring: plan on a pro install
$500 to $1,000, live price on Amazon
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Modine Hot Dawg HD45 Natural Gas Garage Heater
- gas
- Vented, power exhaust
- 80% efficient
- Natural gas
+1 moreFewer
- Low profile
45,000 BTU, 80 percent efficient, certified for residential use. Power exhaust lets a small vent pipe run out a side wall or the roof. Vent kit and thermostat sold separately. $1,000 to $2,000.
- 80% efficient, certified for residential use
- Power exhaust: side-wall or roof venting with small pipe
- Quiet, low-profile cabinet
- Vent kit and thermostat are separate; needs a pro install
- Natural gas version; propane is a separate model
$1,000 to $2,000, live price on Amazon
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Mr. Heater Thermostat for Garage Unit Heaters
Mr. Heater's programmable wall thermostat for its garage unit heaters. under $100.
- Made for Mr. Heater garage unit heaters
- Programmable
Under $100, live price on Amazon
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Running a Buddy heater from a 20 lb tank
A 1 lb cylinder lasts about 5 hours on a Big Buddy's 4,000 BTU low setting (91,500 BTU per gallon, about 21,600 BTU in a pound of propane) but only about an hour on 18,000 BTU. For regular use, run it from a 20 lb tank. Mr. Heater lists its in-line fuel filter as required when a Buddy runs on a hose.
Mr. Heater 12 ft Propane Hose for Buddy Heaters (F273704)
12 ft hose from the heater's 1 inch-20 cylinder fitting to a tank's POL valve, with an excess flow fitting. under $100.
- 12 ft hose, 1 inch-20 male to POL with handwheel
- Excess flow POL fitting
- Rated for appliances up to 75,000 BTU
Under $100, live price on Amazon
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Mr. Heater Fuel Filter for Buddy Heaters (F276163)
Goes between the Buddy's regulator and the hose. under $100.
- Listed as required with Buddy heaters on a hose
- Connects to Buddy regulators and hoses
- Does not connect directly to a tank
Under $100, live price on Amazon
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Flame King YSN230 20 lb Propane Tank with Gauge
Steel cylinder with an OPD valve and built-in gauge. Ships empty. under $100.
- Built-in gauge shows what is left
- OPD valve, DOT certified
- Ships empty
Under $100, live price on Amazon
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The bottom line
From published specs and our sizing rules. Not lab tested.
- 1
Insulated 2-car garage
Comfort Zone CZ220BK 5,000 W Ceiling Mount Garage Heater
17,060 BTU, 240V hardwired
Check price on AmazonPaid link
- 2
Walls-only insulation, 2-car
Comfort Zone CZ260ER 10,000 W Ceiling Garage Heater with Remote
34,120 BTU, 240V hardwired
Check price on AmazonPaid link
- 3
Big or uninsulated shops
Mr. Heater Big Maxx 80,000 BTU Vented Garage Unit Heater
80,000 BTU input, vented LP or NG
Check price on AmazonPaid link
- 4
Bench heat from any outlet
Lasko Elite Collection Ceramic Utility Heater CU12510
1,500 watts, 120V plug-in
Check price at LaskoPaid link
Frequently asked questions
How many BTU do I need to heat a 2-car garage?
For a 24 x 24 ft garage with a 9 ft ceiling heated from 0 F to 50 F: about 13,000 BTU fully insulated, 31,200 with only the walls insulated and 44,100 with no insulation. In a warmer climate it scales down with the temperature rise; with a 22 F design low a walls-only 2-car garage needs about 17,500.
Will a 1,500 watt heater heat a garage?
Only a small, insulated one in a mild climate. 1,500 W makes 5,118 BTU an hour, the most a standard outlet allows, which covers a fully insulated 1-car garage heated from 22 F to 50 F (about 3,700 BTU). In a 2-car or uninsulated garage it is spot heat at the bench.
What size electric heater do I need for a 2-car garage?
In a cold climate, a fully insulated 2-car garage needs about 3,800 W, so a 4,800 to 5,000 W 240V heater covers it. With only the walls insulated it needs about 9,100 W, which means a 10,000 W heater on a 60 A circuit. Uninsulated it needs about 12,900 W, more than any single residential electric heater we list.
What breaker and wire does a 240V garage heater need?
The NEC sizes electric heat at 125 percent of its amps. 4,800 to 5,000 W: a 30 A double-pole breaker and 10 AWG copper. 7,500 W: 40 A and 8 AWG. 10,000 W: 60 A and 6 AWG. A plug-in heater goes on the circuit its plug is rated for, such as 20 A for a NEMA 6-20P.
Is a vent-free propane heater safe in an attached garage?
Only with the precautions the makers require. A vent-free heater releases carbon monoxide, CO2 and water vapor into the garage, and an attached garage shares air with the house. Crack a window or door while it runs, keep a CO alarm in the garage and one inside by the door, and mount it at least 18 inches above the floor. A vented heater sends the exhaust outside instead.
Is it cheaper to heat a garage with propane or electric?
Per 100,000 BTU of heat at US average prices: electricity at 17.3 cents a kWh costs about $5.07, propane at $2.75 a gallon about $3.01 vent-free or $3.76 vented, and natural gas at $1.50 a therm about $1.50 vent-free or $1.88 vented. Electric costs the least to buy and install if the garage already has 240V.
How much does it cost to heat a garage per month?
A 2-car garage held at 50 F for 4 hours a day in a Chicago-like January (26 F average) takes about $38 a month with electric heat at 17.3 cents a kWh if it is fully insulated, about $91 with walls only and about $129 uninsulated. Vented natural gas cuts the walls-only figure to about $34 and vented propane to about $67.
Infrared or forced-air garage heater?
Infrared (radiant) heaters warm people and surfaces in their line of sight, so they feel warm quickly in a drafty garage and keep working when the door opens. Forced-air heaters warm the air, which suits an insulated garage you keep closed and want evenly warm.
24 products are linked on this page. We have not lab-tested these products; picks are based on published specifications and our sizing rules. Amazon prices change, so we show a range and link to the live price. See our disclosure.
Size it for your home
Marcus Reed
Founder and Editor, CrunchYourDollars
Marcus Reed builds the sizing tools on CrunchYourDollars. He is a software engineer with a long-running PC hardware and power supply habit, which is where the watts, watt-hours and surge math on this site comes from. Product specs are pulled from manufacturer data sheets, electricity rates from the U.S. Energy Information Administration, and water chemistry rules from the Water Quality Association. He is not a licensed electrician or plumber: the tools show the math and the matching models so you can make the call, and anything involving your electrical panel should be checked by a licensed pro.
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