Best Garage Heater: 240V Electric, Propane or a Mini-Split

For session heat in a typical attached garage, a 240V fan heater on its own circuit is still the best value, as long as the garage is insulated and the fuel lives somewhere else. For a garage you keep warm all winter, it isn't: a mini-split costs many times more up front, then quietly wins on every hour it runs.

Most garage heater shopping starts with a number on a box and ends with a breaker panel. A 5,000 W ceiling heater is cheap; the 30 A circuit, the electrician and maybe the permit are not. A propane heater skips the wiring but brings water vapor, carbon monoxide and an indoor rating that may not cover a garage at all.

Our garage heater reviews cover four 240V electric heaters (the Comfort Zone CZ220 and CZ230ER, the Fahrenheat FUH54, the Dr. Infrared DR-988 and the Dr. Infrared DR-975), the vented Mr. Heater Big Maxx gas unit heater, and the Mr. Heater Big Buddy propane heater, whose maker's product page pitches it for garages and workshops. Pick the kind of heat before the model: the circuit, the fuel and the hours you run it each winter decide more than the brand does.

Fix the building before you buy heat

Insulate the walls and ceiling, put an insulated door on, and seal the gaps before you size a heater. It's the advice garage owners repeat more than any other, and we agree with it. An electric heater makes a fixed amount of heat. In a bare-stud garage with a drafty door, a big share of it goes into the framing, the roof and a cold slab, and the warm air you do make collects at the ceiling.

Without insulation, electric heat is slow and uneven, and owner results in untouched garages run from usable to hopeless:

Treat the good results as the best case for a garage you haven't touched.

If you can't insulate, or the door is up half the day, heat yourself instead of the air. Radiant or infrared heaters warm the person and the bench rather than the air, and the owners who use them like them; one in Quebec says a small infrared heater worked so well they stopped using their 5,000 W ceiling fan heater. We haven't reviewed an infrared garage heater yet, so none appears in our picks.

Ceiling fans to push warm air down are hit or miss. Some owners use small ceiling or box fans to move the warm air down to where they work, but one who tested with temperature sensors found a fan did little to reduce stratification at speeds slow enough not to feel like a breeze.

How much heater: watts, BTU and the 10 W rule

An electric resistance heater turns every watt into 3.412 BTU/h, at any outdoor temperature. That makes sizing easy to compare across brands, and it means a 5,000 W heater makes the same 17,060 BTU/h whether it's 40°F or -10°F outside. What changes is how fast the garage loses it.

A proper heat-loss calculation is the right way to size. A common rough rule for garage heaters is about 10 watts per square foot, and it's only that: a rule of thumb that assumes a reasonably insulated space. By that rule:

The rule is rough. One owner with a 5,000 W heater in a 16 x 22 ft shop, 352 sq ft and about 90% insulated, says it's barely keeping up in winter, even though the rule says 3,520 W should do. At the other end, an owner with a fully insulated 30 x 30 ft garage and 12 ft ceilings says a 10,000 W heater holds 70°F into the single digits, about 11 W per square foot. Insulation, ceiling height and the door move the answer more than the rule admits.

Check three details that the wattage hides.

• Turndown: the CZ220 steps down to 3,000 W, 60% of full power, and the DR-975 drops to 4,700 W (63%), but the CZ230ER's LOW is still 6,250 W, 83% of HIGH, so in a smaller garage it mostly cycles at near full power.
• Voltage: a heater rated at 240V makes about 75% as much heat on 208V, which is why the FUH54's manual lists 3,750 W there. Comfort Zone's manuals give one rating across 208-240V and the DR-988's manual rates it at 240V only, so neither publishes a separate 208V wattage.
• The low end of the thermostat: if you want the garage held just above freezing, the CZ230ER and FUH54 thermostats have published ranges that bottom out at 45°F, and the DR-975's remote thermostat bottoms out at 50°F per its product page, while the CZ220's knob has no published range at all. The DR-988's thermostat goes down to 37°F, but its manual says not to leave it running unattended for long periods.

The circuit costs more than the heater

Every heater here needs a properly sized 240V circuit, both Dr. Infrared manuals call for a dedicated one, and the manuals are specific. Read them before you buy and hand them to whoever quotes the work:

That wiring belongs to a licensed electrician, and in most places the circuit needs a permit and an inspection; check with your local building department. We won't give wiring steps. What we will say is that the shortcuts people ask about don't work. Running the 7,500 W CZ230ER from an existing NEMA 6-20 receptacle is out: at 31.3 A it's far past a 20 A circuit. So is hanging a CZ220 in a pole barn off an old three-prong welder receptacle, because that type of receptacle has no ground, and the CZ220 manual says the heater must be grounded and hardwired.

Panel capacity sets a ceiling on electric heat, too. A 7,500 W heater on a 40 A circuit is a real share of a small garage subpanel, and one shopper on a 60 A garage feed preferred a 6,000 W heater over a 7,500 W one for the smaller breaker and wire. It also explains why big shops burn gas: a 200,000 BTU/h shop heater would be about 58.6 kW of electric heat, more than the 48 kW a whole 200 A, 240V house service can deliver.

Get the electrician's price for both sizes before you choose a heater. On a long run or a full panel, the 40 A circuit for a 7,500 W heater can cost more than the difference between the heaters, and that's the number that should decide between 5,000 and 7,500 W.

Gas cans, paint, dust and clearances

This is where garages and heater manuals collide. The CZ220 manual says the heater is "FOR INDOOR USE ONLY, IN A DRY LOCATION FREE OF GASOLINE, PAINT, FLAMMABLE LIQUIDS OR COMBUSTIBLE DUST OR MATERIALS." The FUH54 and DR-988 manuals both warn that a heater has hot and arcing or sparking parts inside: "Do not use it in areas where gasoline, paint, or flammable liquids are used or stored." The DR-975 manual adds flammable vapors to the list.

That covers every electric heater we've reviewed, so switching brands doesn't get you out of it. Move the fuel: the gas cans, the mower and snowblower fuel, the paint shelf and the solvents go to a shed or another space the heater doesn't run in. If you spray finishes or paint in the garage, plan that around the heater too. One owner who does woodworking and painting likes their sealed gas heater because it uses outside air; if you go that way, check that heater's own manual for what it allows.

Dust is the woodshop version of the same problem. The Comfort Zone manuals exclude combustible dust outright, and the FUH54 manual says sawdust and drywall sanding dust will permanently damage the heater if you use it to dry out a renovation. Run your dust collection hard and keep the heater away from the sanding station.

Living space is the other limit. Both Dr. Infrared manuals warn "DO NOT USE AS A RESIDENTIAL OR HOUSEHOLD HEATER," and the DR-988's cover adds that it's a floor heater only. Neither defines household; we read it as ruling out a garage that's been converted into living space, so if that's your plan, pick a Comfort Zone or Fahrenheat or get the maker's answer in writing.

Clearances and mounting heights vary by model, so read the manual before you pick a spot:

Both Comfort Zone manuals say to run the heater with a working smoke detector nearby.

Manuals don't all agree on height, and that catches people. One owner bought a 7,500 W heater and then found its manual wanted the bottom of the heater 8 ft from the floor, while other brands and their local code said 6 ft; their ceiling is 8 ft 6 in, which put the heater at about 7 ft. Their local code also says to follow the manufacturer's instructions, so the manual wins. Check the height against your ceiling before you buy, not after.

Know what the overheat light means before it comes on. The FUH54 manual says that if the alarm light is on, turn the heater off immediately and look for anything blocking its airflow; don't run it with the light on, and stop using it if the thermal limit trips repeatedly. The DR-988 manual says to switch off, unplug, let it cool, clear anything near it and wait 30 minutes, and not to operate a heater after it malfunctions. The CZ230ER manual points to blocked airflow or too little clearance first. Clear it once; if it keeps tripping, have the heater and circuit checked rather than resetting it all winter.

Propane and other combustion heat

Portable propane looks like the easy way out of the wiring, and for a closed garage it mostly isn't. The Mr. Heater Big Buddy is a good heater, but its US manual's indoor statement covers small recreational enclosures (porches, cabins, fishing huts, trailers, tents, truck caps and vans) and emergency indoor heating on a 1 lb cylinder. A garage isn't on that list, even though Mr. Heater's product page names garages and workshops. Even where it does allow indoor use, it needs 18 sq in of venting at the ceiling and at floor level, and the US manual carries a notice that it's not for use in a dwelling home in California. The Massachusetts and Canada version of the same heater ships with a manual that says For Outdoor Use Only. The CPSC's rule is plain: never use portable fuel-burning camping equipment inside a home, garage, vehicle or tent unless it's specifically designed for use in an enclosed space and provides instructions for safe use there.

Any vent-free or unvented combustion heater, portable or wall-mounted, needs the ventilation its own manual specifies, every time it runs, plus a battery CO alarm listed to UL 2034 (check the package). The CPSC says a CO alarm is no substitute for proper use of the appliance, doesn't recommend mounting one above a fuel-burning appliance, and never to run unvented fuel-burning appliances in a room where people sleep. Expect moisture as well: the EPA notes that combustion appliances produce water vapor and raise humidity unless vented outside, which is bad news in a garage full of cast iron and hand tools.

Owners who've tried unvented or portable combustion heat in a garage describe exactly those problems: lightheadedness after a few hours with a torpedo heater, tools dripping with condensation, and fumes bad enough to push two of them toward indirect-fired or natural gas heat. One owner got CO symptoms with the double door open about 3 feet. The usual owner advice is to get a heater rated for indoors and a CO detector. We'd go further: indoor-rated isn't the same as rated for your garage, so read what the manual says about the space and the ventilation before you light it.

The combustion heat we'd consider for a garage is a vented gas unit heater: a hanging natural gas or propane heater that sends its exhaust outside through a flue, and on some models takes its combustion air from outside too. Owners of hanging gas heaters, most of them vented unit heaters, like how fast they work, with reports of five, ten and fifteen minutes to warm the space. It's a different project, though: a gas line or a large tank, power for the fan and controls, venting run exactly as the manual specifies, and a gas fitter or HVAC contractor to install it. One owner who skipped a pipe kit at install to save money suspects that's why their heater drips condensation on cold, windy days. The one we've reviewed is the Mr. Heater Big Maxx MHU50: 40,000 BTU/h of vented heat for a two- or three-car garage, at less than half a Modine's listing price, with flame-sensor lockouts as its routine nuisance. Our Big Maxx review covers the install it needs.

Running cost: 240V heat against a cold-climate heat pump

A 5,000 W heater uses 5 kWh for every hour its element is on, so at full power the cost per hour is five times your electric rate. Two owners put their 7,500 W and 8,500 W heaters at about $1.50 an hour, which works out to roughly 18-20 cents per kWh. Thermostat cycling brings the hourly cost down once the garage is warm.

Used in sessions, that's a small bill. Take 100 hours a winter at full power on a 5,000 W heater: 500 kWh, about $75 at an example rate of 15 cents. Held warm around the clock, it isn't small. One owner spent about $120 in a month keeping a well-insulated 20 x 40 ft space at 50-60°F with a 6,000 W heater, and an insulated 28 x 36 ft garage with a 10,000 W heater ran its owner's bill well over $300, more than half of it the garage by their estimate.

A heat pump moves heat instead of making it. ENERGY STAR's cold-climate criteria and NEEP's cold-climate specification both require a coefficient of performance (COP) of at least 1.75 at 5°F, meaning 1.75 units of heat per unit of electricity. Making the CZ220's 17,060 BTU/h at that floor takes about 2.86 kW instead of 5 kW, 43% less electricity on a 5°F night. Some models beat the floor: ENERGY STAR lists the 115V 12K Della Serena at a COP of 2.10 at 5°F, about 52% less electricity than resistance heat for the same output. Not every mini-split meets those criteria, so check a specific model's listing.

Now the payback. On the 100-hour session garage, a heat pump at the 1.75 floor saves about 215 kWh a year, roughly $32 at 15 cents. Against a mini-split that costs many times what a heater does, that's decades, which is the answer a garage owner in Montreal got when comparing a heat pump quote with a resistance heater. On the $120-a-month, always-warm garage, the same floor cuts that bill to about $69 or less. That's at least $50 a month, roughly $250 or more over a five-month heating season, which pays a mini-split back in years rather than decades.

When a mini-split is the better answer

Owners who heat a garage, shop or outbuilding with a mini-split are mostly enthusiastic about it. One pulled out a 5,000 W heater mid-renovation, put in a mini-split and called it far more efficient, with cooling as a bonus. We'd buy one, such as the MrCool DIY 5th Gen, when any of these is true:

• You heat the garage most days, or keep it above freezing all winter. That's where the running-cost gap pays for the equipment.
• You want summer cooling or dehumidifying. No heater does that, and in a garage gym or a woodshop it's half the value.
• The garage is insulated with a decent door. A mini-split has modest output; the owner whose uninsulated shipping-container shop has one says it can't keep up summer or winter.
• You can live with the install. A pre-charged quick-connect kit like the MrCool skips the vacuum pump, but it still needs a circuit, a wall penetration and a pad or bracket for the outdoor unit.

Check the cold-weather numbers before you count on it. NEEP lists the MrCool DIY 5th Gen 12K at 8,400 BTU/h at 5°F (rated and maximum), less than half of a CZ220's 17,060 BTU/h, and at a maximum of 3,800 BTU/h at -13°F, the bottom of MrCool's published heating range. The 18K, a 208/230V unit, is rated at 12,800 BTU/h at 5°F. Size it from a heat-loss estimate for the garage, not by matching a heater's wattage, because a mini-split that's too big short-cycles; but don't expect a 12K to replace a 5,000 W heater on the coldest night. Even happy owners run into limits: about 2 hours to bring a shop from 45°F to 60-65°F on cold days, a 60 x 60 ft shop where the heat pump is undersized for heat and a propane unit heater kicks on as backup, and a shop that never gets hot, just comfortable in a sweatshirt.

In a very cold climate, keep the heater. In the coldest snaps a cold-climate unit's output drops right when you need it, and a resistance heater doesn't care. One owner kept their old Fahrenheat after installing a mini-split, and the 60 x 60 ft shop owner runs propane when it drops into the 30s. If you heat a garage only on weekends where power is cheap, the heater alone is the sensible buy.

Which one we'd buy

• Attached one- or two-car garage, heated a few hours at a time: the Comfort Zone CZ220 on a 30 A circuit.
• You already have a 30 A 6-30R receptacle, or want a heater you can store in summer: the Dr. Infrared DR-988, if you can accept floor use only, no living space and not leaving it running unattended for long.
• Bigger or colder garage, around 750 sq ft by the rule of thumb: the Dr. Infrared DR-975, whose 4,700 W low setting handles mild days better than the CZ230ER.
• You heat often and want long element coverage: the Fahrenheat FUH54, knowing owners report control cycling and the non-element parts carry 1 year.
• Daily heat, or you want cooling: a cold-climate mini-split such as the MrCool DIY 5th Gen 12K, sized to the garage.
• Gas at the garage and long hours: a vented gas unit heater such as the Mr. Heater Big Maxx MHU50, installed by a pro.

Whatever you pick, mount a smoke alarm, and a CO alarm if anything burns fuel in or near the garage, and move the gasoline before the first cold morning.