Garage Heater Power Requirements at a Glance#
A fan-forced garage heater comes in two very different circuits. The mounted 240-volt version is hardwired, drawing 20 to 30 amps for 5,000 to 7,000 watts behind a 30 to 40-amp breaker, while a portable 120-volt heater pulls 12 to 15 amps and 1,440 to 1,800 watts on a 15 to 20-amp branch through a 5-15R or 5-20R outlet.
Garage Heater Electrical Specifications#
| Configuration | Voltage | Amps | Watts (max load) | Breaker | Outlet (NEMA) |
|---|---|---|---|---|---|
| 240-volt electric garage heater | 240 V | 20–30 A | 5,000–7,000 W | 30–40 A | Hardwired |
| 120-volt electric garage heater | 120 V | 12–15 A | 1,440–1,800 W | 15–20 A | 5-15R / 5-20R |
A fan-forced garage heater blows warm air off a resistive element to heat a cold slab-floored space, and the mounted 240-volt version hardwires overhead on a circuit sized to its heat rating. A smaller portable heater trades output for the convenience of an ordinary outlet, which is why the two versions land on very different breakers.
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Circuit and Breaker Sizing for the Garage Heater#
The blower and element of the ceiling-mounted 240-volt unit draw 20 to 30 amps, so it takes 10 or 8-gauge copper to a 30 to 40-amp breaker on a branch it never shares. The portable version trades output for convenience, running on 12 to 15 amps that a 15 to 20-amp branch supplies, though it still uses most of that circuit and dislikes company. That gap in draw is exactly why the two land on such different breakers.
Installation and Safety Notes for Garage Heater Wiring#
The 240-volt heater is wired directly overhead to a two-pole breaker and its wall thermostat, which means a new branch and the permit-and-inspection that comes with it. The portable unit simply matches its cord to a 5-15R or 5-20R outlet. Running a ceiling-mounted 240-volt circuit into a garage belongs to a licensed electrician, while plugging in a portable heater is a homeowner task — just give it an outlet it does not share.
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Garage Heater Electrical FAQ#
What breaker does a 240-volt garage heater need?#
A mounted 240-volt garage heater sits on a 30 to 40-amp two-pole breaker, matched to its 20 to 30-amp draw.
Is a mounted garage heater hardwired or plugged in?#
The 240-volt ceiling-mounted version is hardwired to its breaker and thermostat. Only the smaller portable 120-volt heater plugs into an outlet.
How much current does a fan-forced heater pull?#
The mounted 240-volt unit draws 20 to 30 amps, while a portable 120-volt heater pulls 12 to 15. The element does most of the drawing.
Can a small garage heater run on a standard outlet?#
Yes. A portable 120-volt garage heater plugs into a 5-15R or 5-20R outlet, though it uses most of a 15-amp branch and should not share heavily.
Does a garage heater need a dedicated circuit?#
The mounted 240-volt unit always does. A portable heater does not strictly require one but runs best on an outlet it does not share.
What conductor size feeds a ceiling-mounted heater?#
A 240-volt garage heater takes 10 or 8-gauge copper to its 30 to 40-amp breaker, sized to the 20 to 30-amp element and blower draw.
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