Use this page to check attic fan electricity consumption for your own attic fan: enter your wattage, hours of use per day and electricity rate, and press Calculate. You see your daily, monthly and yearly cost plus your yearly kWh consumption. Those same results also cover attic fan power consumption.
Attic fan electricity consumption comes down to one multiplication, watts × hours × your electric rate, and for most homes the answer is a few dollars a month rather than a budget-breaker. This guide walks through the real running cost of an attic fan, the settings that push it up, and how to tell whether the cooling it provides is worth the power it draws.
A typical electric attic fan draws somewhere between 200 and 450 watts, which is less than a large desktop computer and a small fraction of what the air conditioner in your home pulls. The motor is the only real load, so the draw is steady whenever the blades spin. That is why attic fan electricity consumption is easy to predict: once you know the wattage on the nameplate, the rest is arithmetic. For comparison, see how much energy does an electric barbeque grill use.
The answer to "do attic fans use a lot of electricity" therefore depends on how long the fan runs, not on how hard it works. A 270-watt fan that cycles on for four hours costs pennies. The same fan left on around the clock for a month adds a noticeable line to your bill. Wattage is printed on the motor label, and if only amps are listed, multiply by your line voltage (about 120 volts in a US home) to get watts. A fan rated at 2.25 amps pulls roughly 270 watts.
Electricity is billed in kilowatt-hours, so convert watts to kilowatts first by dividing by 1,000. The calculation looks like this:
$$\text{Cost} = \frac{\text{Watts}}{1{,}000} \times \text{Hours} \times \text{Rate per kWh}$$
Your rate is printed on your utility statement. For the worked example in this guide, assume a 16.4 cents per kWh rate, a 270-watt fan, and a 1,400 CFM airflow rating. At nine hours of operation, the fan uses \(0.27 \times 9 = 2.43\) kWh and costs about $0.40 per day.
The table below applies that formula to the same 270-watt fan at four different schedules. Every figure uses the 16.4 cent rate, and a month is counted as 30 days.
| Hours per day | Electricity used per day | Cost per day | Cost per month | Energy per month |
|---|---|---|---|---|
| 4 hours | 1.08 kWh | $0.18 | $5.31 | 32.4 kWh |
| 9 hours | 2.43 kWh | $0.40 | $11.96 | 72.9 kWh |
| 14 hours | 3.78 kWh | $0.62 | $18.60 | 113.4 kWh |
| 24 hours | 6.48 kWh | $1.06 | $31.88 | 194.4 kWh |
Even the continuous case lands near $32 a month, and it only applies if the fan has no timer or thermostat. Over a 120-day summer, the nine-hour schedule adds up to 291.6 kWh and $47.82.
Power draw varies more by fan type than by brand, because the power source and control method change both the draw and the run time.
A hardwired unit taps your home's electrical system and gives the strongest airflow. Larger models pushing 1,200 to 2,000 CFM draw the most power, and an oversized unit can pull conditioned air up through ceiling gaps, which wastes more electricity than the fan itself uses. Match the fan size to the attic and its intake instead of buying the biggest motor on the shelf.
A solar powered fan uses a roof-mounted photovoltaic panel, so its operating cost on your bill is zero. The trade-off is a higher purchase price and weaker output on cloudy afternoons, exactly when the attic may still be hot. Solar attic fans make the most sense where electricity rates are high and the roof gets full sun. Because the panel needs no wiring, the installed price is often recovered through zero grid kilowatt-hours: the 270-watt electric example costs $47.82 over a 120-day summer, and a solar unit costs nothing to run. Plan on little maintenance beyond wiping dust off the panel, since a dirty panel spins slower and moves less air.
Passive attic fans have no motor at all. Wind and rising heat drive a turbine or ridge exhaust, so they add nothing to your bill but also move far less air than a powered unit on a still day.
An attic fan saves electricity only when the heat it removes lowers the work your air conditioning does by more than the fan consumes. In a hot attic, ceiling insulation and ductwork sit in air that can run well above the outdoor temperature, and venting that hot air reduces the heat soaking into the rooms below. Also see how much energy does a vacuum cleaner use.
Using the nine-hour example, the fan costs $11.96 a month. A central air conditioning system drawing about 3 kW costs 3.0 × $0.164 = $0.49 for each hour it runs. Divide the fan's monthly cost by that hourly figure and the fan breaks even if it trims the compressor's runtime by roughly 24 hours a month, or about 49 minutes a day. In a hot, sunny climate with thin attic insulation, that is realistic. In a well-sealed home with a deeply insulated attic floor, it often is not.
Homes with leaky ceilings, recessed lights and open wire penetrations let the fan pull conditioned air out of the living space. The fan then works against your cooling system, and your energy bill goes up instead of down. Sealing the ceiling and adding insulation usually does more for efficiency than any exhaust fan, which is why many building scientists suggest air sealing first. A tighter ceiling lowers the kilowatt-hours both the fan and the cooling system consume, and the added comfort upstairs comes with no extra electricity at all.
Run time is the biggest lever on what the fan costs you, and three controls decide it.
A fan wired straight to a switch and forgotten will run far more hours than one on a thermostat. In winter, a small amount of venting keeps moisture down and helps prevent ice dams, but every extra winter hour is more electricity, so the fan should not run through the coldest weather.
Airflow is measured in CFM, cubic feet per minute. The Home Ventilation Institute recommends enough airflow for about 10 air changes per hour in the attic space, though many installers aim lower for a balanced system. To estimate your target, multiply the attic floor area in square feet by about 0.7 CFM for a simple rule of thumb.
For a 1,800-square-foot attic, that is 1,260 CFM, which the 1,400 CFM example fan covers. The fan only reaches that number if outside air can enter freely, so check your intake openings. Soffit vents supply that air, and the net free area of the soffit should match or exceed what the fan exhausts. If it does not, the fan pulls air up from the house through the ceiling instead, and your HVAC unit pays for it.
A bigger motor does not mean a better result. An undersized intake makes an oversized fan draw more power for less useful air exchange, so you pay for wattage without the benefit. Spreading airflow with a pair of smaller fans, one near each gable, can ventilate the space more evenly while keeping the total draw in check. A blocked or undersized intake also raises the fan's load: a motor that has to fight restricted airflow draws more watts for the same CFM, so a quick check of the soffit openings protects your home's electricity bill as well as the attic.
A whole house fan is a different machine with a different job. It sits in the ceiling and pulls cooler night air through open windows, pushing the warm indoor air into the attic and out through the roof vents. Because it moves a lot more air, it draws more power, commonly 300 to 700 watts. Compare with how many watts does an automatic soap dispenser use.
Plan to install it with a licensed electrician, and give it generous attic vent area or it will strain. The saving comes from how briefly it runs. A 520-watt unit operated for three evening hours uses 1.56 kWh, or about $0.26 a day and $7.68 a month at the example rate. That can replace several hours of air conditioning on mild nights. It works best where evenings are cooler and the air is dry, and it is a poor fit in humid climates. In contrast, a standard attic fan works mostly in the hot afternoon, when the attic is at its worst.
A fan with an electronically commutated motor can deliver the same airflow at much lower wattage. Compare the CFM per watt on the spec sheet: the 1,400 CFM, 270-watt example delivers about 5.2 CFM per watt, and newer designs beat that handily. Better energy efficiency carries over directly to lower cooling costs in every month the fan runs. Moving from 270 to 180 watts at nine hours a day cuts the monthly total from $11.96 to $7.97, a $3.99 drop that, together with lower heating and cooling costs, repays a pricier motor within a few seasons.
Air sealing the ceiling plane and adding attic insulation reduces how much heat reaches the living space in the first place. A cooler attic temperature in a sealed house also means the fan runs for fewer hours.
Find the wattage on the label, set the hours per day your fan actually runs, and apply your local rate. If the monthly cost is more than the drop in your cooling bill, switch to a thermostat control, reduce the run window, or consider a solar unit. Review the result each season because summer and winter schedules differ. A sudden jump in your utility statement with no change in weather or habits can mean a thermostat has failed closed and the fan is running all night.
For most homeowners in hot climates, an attic fan that runs on a thermostat costs between $5 and $20 a month and offers a modest return through lower attic heat, longer roof and shingle life, and less strain on the cooling equipment. In mild climates or tightly sealed homes, the saving is small and the better investment is air sealing and more insulation. Run your own numbers with the formula above before you buy, and treat the result as the benchmark the fan has to beat.