Attic Fan Power Requirements at a Glance#
An attic ventilating fan is a light 120-volt load: a roof-mount powered ventilator draws 2 to 4 amps for 240 to 480 watts on a 15-amp branch through a 5-15R outlet, while a gable-mount fan pulls 3 to 5 amps and 360 to 600 watts on a 15 to 20-amp circuit, usually hardwired.
Attic Fan Electrical Specifications#
| Configuration | Voltage | Amps | Watts (max load) | Breaker | Outlet (NEMA) |
|---|---|---|---|---|---|
| Roof-mount powered attic ventilator | 120 V | 2–4 A | 240–480 W | 15 A | 5-15R |
| Gable-mount attic fan | 120 V | 3–5 A | 360–600 W | 15–20 A | Hardwired |
This small roof or gable motor switches on when a thermostat senses the attic baking in the afternoon, exhausting the hot air so it never soaks down into the rooms below. It runs on a light branch tied to the attic wiring, and the roof-mounted version usually reaches a switched receptacle while the gable unit is more often wired straight in.
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Circuit and Breaker Sizing for the Attic Fan#
At 2 to 5 amps this motor barely troubles a branch, so the existing 14-gauge attic wiring on a 15-amp breaker handles a roof ventilator with room to spare; a gable unit at the top of its range may sit on a 12-gauge 20-amp circuit. Neither version needs a dedicated feed — the fan taps whatever lighting or receptacle branch already runs through the attic. A thermostat in the fan closes the circuit only when the attic bakes, so the load is intermittent and small even on hot afternoons.
Installation and Safety Notes for Attic Fan Wiring#
A roof-mounted ventilator often reaches a switched receptacle in the attic, so it plugs in with a standard 5-15R cap, while a gable fan is more commonly wired straight into a nearby junction box. Because the fan sits in insulation and heat, the connections must be in a proper box and the thermostat rated for the attic's temperature. Swapping a like-for-like fan is within reach of a confident homeowner, but running a new branch or adding the thermostat control is cleaner work for an electrician, and some areas will want it inspected.
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Attic Fan Electrical FAQ#
What breaker does a powered attic ventilator use?#
A roof-mount ventilator sits on a 15-amp branch, and a gable fan on a 15 to 20-amp circuit. Both draw only a few amps, so the breaker is standard.
Is an attic fan hardwired or plugged in?#
It depends on the style. A roof ventilator often plugs into a switched attic receptacle, while a gable-mount fan is usually wired directly into a junction box.
How does the thermostat control the fan?#
A built-in thermostat closes the circuit when the attic heat climbs past its setpoint, running the fan only when it is needed and shutting it off as the space cools.
How much current does a roof ventilator pull?#
A roof-mount powered ventilator draws 2 to 4 amps for 240 to 480 watts. That is a light load even on the hottest afternoon.
Does an attic fan need its own circuit?#
No. At a few amps it shares an existing attic lighting or receptacle branch without any trouble.
How does a gable fan differ from a roof unit electrically?#
A gable fan draws slightly more, 3 to 5 amps, and is more often hardwired than plugged in. Otherwise both are light 120-volt ventilation motors.
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