Roundup · 240 V unit heaters
The heaters that solve a cold garage are not appliances, they are wiring. This is the arithmetic that decides which one you can actually install.
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A 240 V unit heater is the only electric heater that can warm a whole garage, because it is not limited to the 1,500 W an outlet allows. A 5,000 W unit draws 20.8 A and needs a 30 A circuit; 7,500 W draws 31.3 A and needs 40 A. All of them need an electrician.
A unit heater is a fixed appliance: a steel box with a heating element and a fan, bolted to a ceiling or a wall and wired directly to a two-pole 240 V branch circuit. There is no plug, and on every unit here the manual explicitly prohibits extension cords. You do not buy one and use it that evening — you buy one and book an electrician.
The reason the category exists is that 240 V removes the ceiling that makes every plug-in heater the same 1,500 W. Power is volts times amps, so doubling the voltage buys you twice the wattage for the same current. A 7,500 W unit heater pulls 31.3 A at 240 V; the same 7,500 W at 120 V would pull 62.5 A, which is most of a residential service. That is the whole trick, and it is why the answer to a cold garage is a wiring question rather than a shopping one.
Shop this category for an hour and you will meet two different numbers both called “amps,” exactly 25% apart, with nothing on the page telling you which is which. Both are real and they mean different things:
Here is every wattage in this class with both figures side by side, plus the smallest standard breaker that covers it. Breakers are only made in the sizes listed in NEC 240.6(A), so the answer is always the next size up from the ampacity, never the ampacity itself.
| Rated power | Draw at 240 V | Minimum circuit ampacity | Smallest standard breaker | Output |
|---|---|---|---|---|
| 3,000 W | 12.5 A | 15.6 A | 20 A | 10,236 BTU/h |
| 4,000 W | 16.7 A | 20.8 A | 25 A | 13,649 BTU/h |
| 5,000 W | 20.8 A | 26.0 A | 30 A | 17,061 BTU/h |
| 6,000 W | 25.0 A | 31.3 A | 35 A | 20,473 BTU/h |
| 7,500 W | 31.3 A | 39.1 A | 40 A | 25,591 BTU/h |
| 10,000 W | 41.7 A | 52.1 A | 60 A | 34,121 BTU/h |
Draw computed as watts / 240 V. Minimum circuit ampacity is 125% of the draw, per the NEC continuous-load rule (NFPA 70, 210.19(A)(1) and 210.20(A)); the breaker column is the smallest standard rating at or above it (240.6(A)). Confirm against your own unit's rating plate and manual — the installer sizes the conductors.
The good manuals publish both numbers and keep them apart. Comfort Zone's CZ220 manual gives a 20.9 A draw at 5,000 W and then, on its own line, a recommended 30 A breaker. Its CZ230ER manual gives 31.3 A at 7,500 W and a recommended 40 A breaker. Those are exactly the values in the table above, arrived at independently — which is a useful check on our arithmetic and on theirs.
The rest of the category is less careful. Fahrenheat's listings print 26.1 A as the FUH54's amperage, which is the circuit figure for a heater that draws 20.8 A — we worked through that one in its review. Dura Heat goes further and puts “40 A” in the product name of a 7,500 W heater that draws 31.3 A.
A garage sits outside the heated envelope, so the sizing rule gets the 1.5 multiplier: 15 W per square foot rather than the 10 W we use for a room inside the house. That correction is most of the reason garage shopping goes wrong, because the coverage claims on these listings are computed the other way.
| Room size | Watts needed | BTU/h | Plug-in heaters |
|---|---|---|---|
| 240 sq ft | 3,600 W | 12,284 | 3 (different circuits) |
| 400 sq ft | 6,000 W | 20,473 | 4 (different circuits) |
| 500 sq ft | 7,500 W | 25,591 | 5 (different circuits) |
| 600 sq ft | 9,000 W | 30,709 | 6 (different circuits) |
| 720 sq ft | 10,800 W | 36,851 | 8 (different circuits) |
Computed as square feet x 10 W x insulation factor x (ceiling / 8 ft), for an unheated space (garage, unfinished basement) — 15 W/sq ft, 8 ft ceiling. Heater count assumes the 1,500 W plug-in ceiling.
A single-car garage at roughly 240 sq ft wants about 3,600 W — the 5,000 W picks here, run on a middle setting. A standard two-car at 400–600 sq ft wants 6,000–9,000 W, which is the 6,000 W and 7,500 W units and, at the top of that range, more than any single one of them delivers. If your garage is at the large end and genuinely cold, size to what the panel allows and accept a longer warm-up rather than buying two heaters and two circuits.
These are the largest loads on this site by a wide margin, and the honest framing is that the running cost is fine and the capacity is the problem — the opposite of how the category is usually discussed.
| Wattage | Per hour | 1 h | 2 h | 4 h | 8 h |
|---|---|---|---|---|---|
| 1,500 W | 27.5¢ | $0.28 | $0.55 | $1.10 | $2.20 |
| 5,000 W | 91.7¢ | $0.92 | $1.83 | $3.67 | $7.34 |
| 6,000 W | 110.0¢ | $1.10 | $2.20 | $4.40 | $8.80 |
| 7,500 W | 137.6¢ | $1.38 | $2.75 | $5.50 | $11.00 |
Computed at 18.34¢/kWh — the U.S. residential average for June 2026 (EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026). Your rate is on your own bill; substitute it and the arithmetic still holds. Figures assume full output for the whole period.
Two hours in the garage on a Saturday costs about $1.83 on the 5,000 W unit and $2.75 on the 7,500 W one. That is a reasonable price for a warm garage. What you should not do is leave one running all day: eight hours at 7,500 W is $11.00, and a garage nobody is standing in does not need to be warm. This is the category where a timer earns its keep, which is why the 12-hour auto shut-off on our 7,500 W pick counts as a cost feature rather than a convenience one.
The rate behind every figure on this site
18.34¢per kilowatt-hour
U.S. residential average for June 2026. EIA, Electric Power Monthly, Table 5.6.A, released August 26, 2026.
This is the most recent month EIA has published. Residential rates move seasonally and vary enormously by state — from roughly a dime per kilowatt-hour in parts of the South to more than 40¢ in Hawaii — so treat it as a national reference point, not as your rate.
Ranked for fit, not for hype. Coverage and current draw are computed from each unit’s published wattage. Tap a row for the full write-up, or go straight to the listing.
| # | Product | Best for | Covers | Draw | Price |
|---|---|---|---|---|---|
| 1 |  Comfort Zone CZ220BKThe spec sheet every other maker in this class should copy: three wattage settings, the draw for each, and the breaker size as a separate line so the two cannot be confused. | The cheapest honest way to 5,000 W | 500 sq ft | 20.8 A | $106.67 · Check on Amazon |
| 2 |  Dr. Infrared DR-966The pick if a published listing mark matters to you, which on a hardwired ceiling appliance it reasonably might — but read the brand name as a brand name, because this model is not infrared. | The only one with a real safety listing | 600 sq ft | 25.0 A | $175.70 · Check on Amazon |
| 3 |  Comfort Zone CZ230ERBK7,500 W with a digital thermostat, a remote and a 12-hour timer for less than the 5,000 W units cost — and its manual specifies the 40 A breaker and 8 AWG wire the load actually needs. | A cold two-car garage | 750 sq ft | 31.3 A | $155.00 · Check on Amazon |
| 4 |  Fahrenheat FUH54The honest answer to garage heating: 5,000 W on a 240 V circuit is 3.3 times what any outlet can deliver, which is why plug-in heaters never work out there. | A garage that actually gets warm | 500 sq ft | 20.8 A | $686.00 · Check on Amazon |
Coverage computed at 10 W/sq ft, average insulation, 8 ft ceiling. Draw computed as watts ÷ volts. Neither figure is a manufacturer claim.
Top pick · The cheapest honest way to 5,000 W
The spec sheet every other maker in this class should copy: three wattage settings, the draw for each, and the breaker size as a separate line so the two cannot be confused.
| Published specification | |
|---|---|
| Rated power | 5,000 / 4,000 / 3,000 W, switch-selected at 208–240 V |
| Current draw (maker's figures) | 20.9 A / 16.7 A / 12.5 A — matches 5,000 ÷ 240 = 20.8 A |
| Recommended circuit breaker | 30 A or larger, per the manual — the maker's 20.9 A draw grossed up by the NEC continuous-load rule is 26.1 A |
| Recommended wire | 10 AWG copper only, rated 167°F/75°C or larger, per the manual |
| Published output | 17,060 / 13,650 / 10,240 BTU/h |
| Horizontal air throw | 18 ft (approximate), per the manual |
| Thermostat | Mechanical knob, turned down until it clicks off. No set-point scale published |
| Clearances | No closer than 8 in to a vertical surface, no lower than 6 ft from the floor |
| Weight | 25–30 lb (approximate), per the manual |
| Warranty | One year against defects in quality or workmanship (World and Main) |
| Installation | Hardwired, ceiling- or wall-mounted. No plug, and extension cords are prohibited |
| Heat type | Fan-forced |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | The Amazon listing says “ETL Compliant”. The CZ220 Series manual names no certification mark, and “compliant” is a weaker claim than “listed” — see [UL vs ETL](/safety/ul-vs-etl). As with any hardwired 240 V unit, the rating plate is what the installer works from. |
Who it is for
A one- or two-car garage where you want the wiring done once, correctly, at the lowest hardware cost — and you would rather have three wattage settings than a digital display.
What it is not for
Anyone who wants to dial in a temperature, or who needs a published listing mark in the manufacturer's own documentation before a hardwired appliance goes on their ceiling.
Sources for this entry
2 · The only one with a real safety listing
The pick if a published listing mark matters to you, which on a hardwired ceiling appliance it reasonably might — but read the brand name as a brand name, because this model is not infrared.
| Published specification | |
|---|---|
| Rated power | 6,000 W high / 3,000 W low at 240 V, single phase |
| Current draw | 25.0 A high, 12.5 A low — our figures (6,000 ÷ 240). The maker publishes no amperage |
| Minimum circuit ampacity | 31.3 A — 125% of the draw under the NEC continuous-load rule, which needs a 35 A breaker |
| Recommended wire | 8 AWG copper, per the manufacturer |
| Output | 20,473 BTU/h at 6,000 W — our figure; the maker publishes no BTU rating |
| Maker's coverage claim | 600 sq ft |
| Heating element | Spiral steel metal sheath behind an 8 in fan, with 5 adjustable louvers |
| Thermostat | Built-in adjustable, 37–104°F |
| Dimensions | 14.5 in high × 13 in wide × 14.5 in deep |
| Warranty | One-year limited component warranty |
| Installation | Hardwired, no power cord supplied. Ceiling and wall brackets included |
| Heat type | Fan-forced |
| Maker’s coverage claim | 600 sq ft |
| Safety listing | UL and cUL Listed, per the manufacturer's own specification. |
Who it is for
A garage or workshop where a published UL listing is the deciding factor, and where you want a thermostat you can set to a number and leave.
What it is not for
Anyone buying it for radiant heat because of the brand name — this is a fan-forced unit, and the radiant strategy for a garage is a different product entirely.
Sources for this entry
3 · A cold two-car garage
7,500 W with a digital thermostat, a remote and a 12-hour timer for less than the 5,000 W units cost — and its manual specifies the 40 A breaker and 8 AWG wire the load actually needs.
| Published specification | |
|---|---|
| Rated power | 7,500 W high (default) / 6,250 W low at 208–240 V |
| Current draw (maker's figures) | 31.3 A high / 26 A low — matches 7,500 ÷ 240 = 31.3 A |
| Recommended circuit breaker | 40 A or larger, per the manual — the draw grossed up by the NEC continuous-load rule is 39.1 A |
| Recommended wire | 8 AWG copper only, rated 167°F/75°C or larger, per the manual |
| Published output | 25,590 BTU/h high / 21,240 BTU/h low |
| Horizontal air throw | 18 ft (approximate), per the manual |
| Controls | Digital thermostat with an LED ambient-temperature display, remote, 12-hour timer with auto shut-off, fan-only mode. No set-point scale published |
| Weight | 25–30 lb (approximate), per the manual |
| Warranty | One year against defects in quality or workmanship (World and Main) |
| Installation | Hardwired, ceiling- or wall-mounted. No plug, and extension cords are prohibited |
| Heat type | Fan-forced |
| Maker’s coverage claim | None published — the coverage figure above is ours |
| Safety listing | Neither the listing nor the CZ230ER Series manual names a certification mark. On a hardwired 240 V unit the rating plate is what the installer works from. |
Who it is for
A two-car garage, a shop or an outbuilding of roughly 400–600 sq ft where you want it genuinely warm, and you have 40 A of two-pole space in the panel.
What it is not for
A single-car garage or a panel that is already full — 7,500 W is more heat than a small space needs and more current than a tight panel can give.
Sources for this entry
4 · A garage that actually gets warm
The honest answer to garage heating: 5,000 W on a 240 V circuit is 3.3 times what any outlet can deliver, which is why plug-in heaters never work out there.
| Published specification | |
|---|---|
| Rated power | 5,000 W at 240 V (also configurable at 2,500 W) |
| Current draw | 20.8 A at 240 V (5,000 ÷ 240) |
| Minimum circuit ampacity | 26.1 A — 125% of the draw under the NEC continuous-load rule; sets the breaker |
| Published output | 17,065 BTU/h |
| Maker's coverage claim | 500 sq ft |
| Installation | Hardwired, ceiling- or wall-mounted. Not a plug-in appliance |
| Heat type | Fan-forced |
| Maker’s coverage claim | 500 sq ft |
| Safety listing | No listing mark published in the listing text; a hardwired 240 V unit must be installed to NEC and its rating plate checked by whoever wires it. |
Who it is for
A garage, workshop or outbuilding you want genuinely warm, where you have panel capacity and are willing to pay an electrician.
What it is not for
Anyone looking for a plug-in solution. If you want to plug it in, this is not the product and no product is — read the garage roundup first.
Sources for this entry
Our 7,500 W pick is sold twice. One listing calls it the CZ230ERBK and one calls it the CZ230ER; the titles are otherwise word-for-word identical, the suffix is the colorway, and the manual covers both. On the day we checked, the two were priced about $10 apart and only one of them was in stock — and which one is cheaper moves. We pin the listing that was actually shipping, but before you buy, open both and take the better deal.
This is not unique to Comfort Zone; we found the same pattern on Pelonis oil-filled radiators with a much wider gap. It is worth thirty seconds on any heater whose model number ends in a color code.
Every roundup on this site names something to skip. It costs us nothing to publish and it is the fastest way to tell whether a buying guide was written for you or for its commission.
The Dura Heat EWH7500
It is the closest competitor to our 7,500 W pick and it costs more, which would be fine if its documentation were better. It is not. The model name itself reads “7500 W, 40 A” — but 7,500 W at 240 V draws 31.3 A, and 40 A is the breaker the continuous-load rule calls for, so the figure in the product name is the circuit rating presented as though it were the draw. Its own distributor page then states the coverage twice, as “up to 900 sq. ft.” in the description and “1,100 sq. ft.” in the specification table, and both are generous against 7,500 W. The heater may well be fine; a buyer trying to brief an electrician from that page is not.
Any unit heater whose maker publishes no manual
The cheapest 240 V listings run 20–40% below the picks here, and several of them do not put a model number in the title at all, which means there is no document to look up and no specification to hold anyone to. On a portable heater that is a bad deal. On a fixed appliance that an electrician is about to connect to a two-pole circuit in your ceiling, the manual IS the product — it is where the breaker size, the wire gauge, the lug torque and the clearances live. If you cannot find the manual before you buy, you will not find it when the installer asks.
And what we did not do: we have not tested these units, owned them, measured them or run them in a room. Everything above is compiled from published manufacturer specifications and live retail listings, with the electrical load, room coverage and running cost computed by us from the published wattage. The full method.
We have not published a wire-sizing table, and we are not going to. Conductor sizing depends on the terminal temperature rating, the ambient temperature, how many current-carrying conductors share the raceway and the small-conductor rule in NEC 240.4(D) — none of which we can see from here. What we have done is quote each maker's own recommendation: 10 AWG copper for the 5,000 W Comfort Zone, 8 AWG for its 7,500 W unit, 8 AWG for the 6,000 W Dr. Infrared. Give those to the electrician as a starting point and let them size the run.
Three of these four units have no certification mark we could verify. Only the DR-966's maker publishes one, as UL and cUL Listed. The CZ220's Amazon listing says “ETL Compliant,” which is not the same claim as ETL Listed and does not appear in the manual at all; the CZ230ER's listing and manual name nothing. That is worth knowing and it is not necessarily disqualifying on a hardwired appliance, where the rating plate and the inspection are what stand between you and a bad install — but it is a real difference between the picks, and the difference between “listed” and “compliant” is not cosmetic.
And we have not stood in a garage with any of them. Every figure on this page is either published by the manufacturer, and attributed, or computed by us from the rated wattage, and shown. Nobody here has measured an air temperature or timed a warm-up.
A 30 A two-pole breaker. The heater draws 20.8 A (5,000 ÷ 240), the NEC continuous-load rule requires the circuit to be sized at 125% of that, which is 26.0 A, and the smallest standard breaker above it is 30 A. Comfort Zone's own manual specifies 30 A for its 5,000 W unit, which agrees.
A 40 A two-pole breaker. 7,500 ÷ 240 = 31.3 A of draw, 125% of that is 39.1 A, and the next standard breaker size up is 40 A. The Comfort Zone CZ230ER manual specifies 40 A and 8 AWG copper.
Because one is the current draw and the other is the minimum circuit ampacity, and they are 25% apart. A 5,000 W heater draws 20.8 A but needs a circuit rated for about 26 A, and you will see either figure printed as “amps” depending on the listing. Divide the wattage by 240 yourself and you will always know which number you are looking at.
Not the ones on this page — all four are hardwired, and their manuals prohibit extension cords. A handful of 240 V heaters do ship with a NEMA plug for an existing dryer or welder outlet, which saves you the wiring but ties the heater to that one location. Everything here assumes a dedicated circuit.
About 91.7 cents an hour at our published rate of 18.34 cents per kWh, so roughly $1.83 for a two-hour session. A 7,500 W unit is about $1.38 an hour. Running cost is rarely the constraint in this category — panel capacity is.
It is better at warming the whole space, which a radiant heater will never do. Radiant is better at warming you specifically, cheaply, right now, without an electrician. If you work in the garage for an hour at a time, radiant spot heating is often the smarter buy; if you want the space itself usable, this is the category.
No. All four are fan-forced convection, including the Dr. Infrared DR-966 — the brand name is a brand name, and that model uses spiral metal-sheath elements behind an 8 inch fan. It matters in a leaky garage, because convection heats air that then escapes around the door.
A two-car garage needs about 9,000 W. An outlet gives you 1,500. What to do instead.
5,000 W of real garage heat — and the 26.1 A figure in every listing is the circuit rating, not the draw.
12.5 A against a 12 A continuous limit — the arithmetic nobody publishes, and what to do about it.
Where the 10 W/sq ft rule comes from, when it breaks, and the exact watt-to-BTU conversion.
Cost per hour for any wattage at any rate — the calculator, the formula and the full grid.
Both marks mean the same standard was met. Here is how to check that a listing is real.