Use this page to check whole house fan electricity consumption for your own whole house 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 whole house fan power consumption. Also see food dehydrator electricity consumption.
If your summer bills keep climbing, the whole house fan electricity consumption numbers are worth a close look, because this fan moves a lot of air for very little power. Most homeowners are surprised to learn that a single unit draws a few hundred watts of electricity, a small fraction of the energy that central air conditioning pulls, so the real running cost is usually a few dollars a week. Here is how to work out your own figure, what pushes it up or down, and when the savings are real.
A whole house fan sits in the ceiling between your living space and the attic. When it runs, it pulls warm indoor air up and out through the attic vents while cooler outside air floods in through open windows. Because this whole-house fan relies on natural ventilation instead of removing heat with a compressor, its power draw is modest, and most units deliver 30 to 60 air changes per hour. Whole house fans of every size follow the same basic rule, which is that a bigger motor draws more. Most residential units are rated between about 300 and 1,000 watts, depending on motor size and the airflow (CFM) they are built to deliver. Small, quiet models sit at the low end, and large high-flow models in two-story houses sit at the top.
Your utility never bills you in watts. It bills in kilowatt-hour units, usually written kWh. One kilowatt is 1,000 watts, so a fan drawing 615 watts uses 0.615 kilowatts, and if it runs for one hour it consumes 0.615 kWh. Multiply that by the electricity rate on your utility bill and you have the cost of that hour. Every estimate on this page is built from those three steps: watts, hours, and price per kWh.
The nameplate wattage is the starting figure for estimating how much electricity the fan uses. It appears on the nameplate on the motor housing or in the manual, usually listed per speed setting. A multi-speed unit has one figure for each setting, and the gap between them is large. The low setting of a typical model may use only about 40% of the power of its high setting, which matters because fan speed is one of the few variables you control completely.
To estimate the monthly cost, use this formula and substitute the numbers from your own fan label and utility bill:
$$\text{Monthly cost} = \frac{W}{1000} \times h \times d \times r$$
Here \(W\) is the fan wattage, \(h\) is hours of use per day, \(d\) is the number of days you run it that month, and \(r\) is your electricity rate in dollars per kWh. Dividing by 1,000 converts watts into kilowatts, which is what the rate is based on.
Take a mid-size fan rated at 615 watts in a home where electricity costs $0.158 per kWh. You run it for 5 hours each evening on 26 evenings in the month. The calculation is 0.615 kW × 5 hours × 26 days = 79.95 kWh, and 79.95 kWh × $0.158 = $12.63 per month. In other words, each hour of operation costs about 9.7 cents.
The table below applies the same schedule to three different fan sizes so you can see how the wattage changes the monthly total.
| Fan wattage (W) | Cost per hour | kWh per month | Monthly cost |
|---|---|---|---|
| 385 W (low-power unit) | $0.061 | 50.05 kWh | $7.91 |
| 615 W (mid-size unit) | $0.097 | 79.95 kWh | $12.63 |
| 940 W (high-flow unit) | $0.149 | 122.20 kWh | $19.31 |
Both the hourly cost and the monthly kWh scale in a straight line, so a fan twice as powerful costs twice as much to run, and a rate 20% higher raises the bill by exactly 20%. Assumptions: 5 hours a day, 26 days a month, $0.158 per kWh.
A whole house fan is a seasonal appliance, so the number that matters is the cost per season, not twelve months of it. If the same 615-watt unit runs 5 hours a night for a 105-night cooling season, it uses about 322.9 kWh and costs roughly $51 per year. Compare that with the cooling costs on your energy bills during your hottest weeks and the fan looks inexpensive. Across the country, whole house fans add only a few dollars to home energy bills in a typical season, and whole house fans cost less to run than almost any other cooling option.
The comparison most people care about is the one against the air conditioner. A typical central unit draws somewhere between 2,000 and 5,000 watts while the compressor and blower motor are running, and a figure near 3,100 watts is common for a mid-size home. That is roughly five times the draw of the 615-watt fan from the example above. Efficiency ratings such as SEER describe how much cooling a compressor delivers per watt, but they do not change the fact that the compressor is a high-draw device. The U.S. Department of Energy points out that whole house fans can stand in for air conditioners on mild nights, which is the whole idea behind using them to cool your home with less energy.
Run 3,100 watts for 5 hours on 26 evenings and the air conditioner consumes 403 kWh, which is $63.67 at $0.158 per kWh. The fan, as shown earlier, uses 79.95 kWh and costs $12.63. The difference is about $51 per month, and over a 105-night season it is roughly $206 in energy savings. The fan draws about 20% of the power of the air conditioning system, which lines up with the 10% to 25% range quoted for whole house fans by most efficiency sources.
The fan only cools when the outside air is cooler than the air inside, ideally at least 5 degrees Fahrenheit cooler. On a night that stays above 80 degrees, the fan cannot replace the air conditioner, because it would simply pull in hot outdoor air. Whole house fans are a strong choice for the home owner who has cool nights, but they are not a universal replacement. Treat the savings above as the best case for a dry climate with cool nights, and expect smaller numbers where evenings stay warm and humid.
Two homes with identical fans can see very different bills. Four inputs do most of the work, and then the house itself decides how many hours the fan needs to run. Compare with weighing scale power consumption.
Your electricity rate converts kWh into dollars. Rates around $0.10 to $0.15 are common in some regions and $0.20 to $0.30 in others, so the same fan can cost twice as much to run in one state as in another. If your utility offers time-of-use pricing, evening and early morning hours, when the fan works best, may fall in cheaper off-peak blocks, but check the schedule before you assume so.
Fan speed has the largest effect of anything you can change. A motor on its lowest setting may need only a fraction of its high-speed wattage, and running it low through the night lets walls, floors and furniture shed their stored heat. Dropping a unit from high to low cuts its wattage and electricity use by roughly 60%, so a longer run on low often uses fewer kWh than a short blast on high.
Hours per day is the simplest lever. Coastal homes with cool nights may need only two to four hours of fan time, while inland homes in a dry climate may run it six to ten hours in the evening to avoid daytime air conditioning altogether. Timers and smart controls cut wasted run time by switching the fan off once the indoor temperature reaches your target.
Dry climate with hot days and cool nights is the ideal match for the fan. Where humidity is high, the fan never dehumidifies the air, so the house can still feel sticky and you may fall back on the air conditioner, which pushes up total energy consumption.
An open floor plan lets the fan move air through the whole house quickly, often evening out the temperature in 10 to 20 minutes. A divided, multi-story home layout needs a longer run or a second unit. Good insulation and a sealed attic floor keep the cool air you have made, which means fewer hours of fan time the next evening.
A whole house fan is often confused with an attic fan, but the two do different jobs. An attic fan sits in the roof or gable and pushes hot air out of the attic, which protects the roof framing and wiring and slightly lowers the temperature of the rooms beneath. A whole house fan is mounted in the ceiling of the living space and ventilates the home itself. Installation of either type should be left to a professional. For comparison, see how much energy does an air conditioner (ac) use.
A ducted unit uses flexible runs to pull air from several rooms into one housing in the attic. It tends to be quieter and can reach distant bedrooms, but the longer path adds resistance, so a ducted system sometimes needs a larger motor and more watts for the same airflow.
A non-ducted unit sits directly over a ceiling opening, usually in a central hallway. It moves air with less resistance, so it typically draws fewer watts for the same airflow than a ducted unit, though it is louder because the motor is close to the living space. Whether the fan is ducted or not, the electricity use follows the same rule: watts times hours times rate.
Good installation depends on the vents as much as the fan, and a careless installation can erase the savings. The attic must have enough vent area to let the air escape, and many installers recommend two to four times the vent space required by code. Without a proper attic ventilation system, the fan strains against back-pressure, runs longer, and wastes power. Adequate attic vents are as much a part of efficient operation as the motor itself.
The following habits keep the operating cost low without sacrificing comfort:
Ceiling fans use only about 15 to 75 watts each, so adding two of them costs a trivial amount compared with running the air conditioning system for an extra hour.
Energy use is only half the picture. The installation of a whole house fan, including the installation of extra vents, is a one-time expense that sits against your yearly savings. Installation cost for a whole house fan usually runs from the high hundreds to a little over a thousand dollars, and you may need extra attic vents. If you pay $1,450 for the whole job and save about $206 a season, the payback period is roughly 7 seasons. A higher electricity rate or a longer cooling season shortens it, which is what makes the return on investment so different from one region to another.
Every hour the fan runs is an hour your air conditioner does not, so a whole house fan can extend your HVAC lifespan and push replacement further out. That benefit is hard to price, but it adds to the overall cost savings.
Because the fan swaps indoor air with outside air, it can refresh stale rooms, but it also draws in outdoor pollen, dust and traffic fumes, so air quality can suffer in some places. A fan also causes depressurization in the home, so open a window near any gas appliance to prevent backdrafts, and consider an air purifier if allergies are a concern. On high-pollen days, running the fan fewer hours also lowers its energy use.
Noise is the most common complaint, especially for non-ducted models run on high at night. A quieter, ducted model on low is a good compromise, and the low setting uses less power too. Many owners find the cooling breeze a clear gain in comfort even before they count the savings, and a working fan can add resale value, since buyers see it as a home feature that lowers energy costs.
A well-maintained fan keeps its rated electricity draw. Routine maintenance is light: keep the louvers clean, check belts and bearings if your model has them, and install the insulated cover in winter to stop heat loss through the ceiling. A well-kept fan stays efficient and draws no more than its rated watts. Check the wattage on the label once a season, and if the motor ever sounds strained or the airflow drops, have it looked at, because a struggling motor quietly draws more power for less cooling.
Whole house fans are among the cheapest ways to cool a house when the climate cooperates. Multiply the fan wattage by your hours of use and your electricity rate, compare the answer with what the air conditioning system would have cost for the same hours, and use low speed and cool evenings to get the most from every kilowatt-hour. Unless your nights stay hot and humid, the running cost of the fan will be a small part of your bill, and the energy savings will outweigh its draw many times over. For a home owner who wants a sustainable way to cool the house, a smaller carbon footprint is a welcome side effect of drawing less energy from the grid.