Do attic fans use a lot of electricity, or do they actually lower your bill?
How can attic fans affect other bills such as the AC bill, heating bill, and maintenance bill?
How much electricity do they draw and what is the cost of running an attic fan?
I’m an electrical engineer and energy manager, and I wrote this short article in order to help answer these questions and know if attic fans are a good addition to your house or not.
Without further ado, let’s begin!
Does an Attic Fan Use a Lot of Electricity?
Generally speaking, attic fans do not use a lot of electricity compared to the other main loads and compared to the home’s total electricity consumption.
An attic fan uses less electricity per hour of operation than an AC unit, a medium-size electric space heater, an electric oven, a dishwasher, or a washing machine, but more than a TV, an efficient lighting unit, or a ceiling fan.
However, it is important to note that some attic fans use more electricity than others depending on many factors such as:
- The rated CFM (cubic feet per minute) of air needed to be moved out by the attic fan.
- The attic space area to be covered.
- Difference in efficiency between different types, models, and brands for the same rating of attic fans.
- The setting or speed you leave the attic fan on.
- Whether it works all the time or if it comes with a thermostat that turns it on and off based on temperature limits.
- Whether it comes with a solar panel to power it for free during the day or it works only on the electricity from the utility meter.
How Much Electricity Does an Attic Fan Use?
An attic fan uses anywhere between 0.03 – 0.3 kWh per hour of operation if it was made with a good level of efficiency, and the value varies depending on the size and type of the attic fan, which is dependent on the attic or roof area and the air volume to be extracted with it.
Assuming you have a 2,300 s.f. roof and you need an attic fan to extract around 1000-1200 CFM (Cubic Feet per Minute), then the attic fan could consume around 30 – 200 Wh (0.03 – 0.2 kWh) per hour of operation, depending on the type (gable / roof) and the manufacturer.
And for a bigger house with an attic or roof of around 3,000-4,000 s.f., where you need an attic fan with the rating of around 2000 CFM or more, the attic fan might consume anywhere between 100 – 300 Wh (0.1 – 0.3 kWh) per hour of operation.
This is the estimated consumption per hour, and the total amount of electricity the attic fan consumes depends on the total hours it operates during the month, and whether it runs on full speed or on one of the lower speeds.
But assuming that you run the attic fan on full speed for 24 hours a day, then based on the previous examples:
- An attic fan for a small-medium size house with an attic area of up to 2,300 s.f. would consume around 22 – 149 kWh per month. (0.03 X 24 X 31 – 0.2 X 24 X 31)
- And for a bigger house, the attic fan consumes around 74 – 223 kWh per month. (0.1 X 24 X 31 – 0.3 X 24 X 31)
Note that these estimates might be a bit on the upper end of the spectrum because usually, attic fans come with a thermostat that would turn on and off the fan based on the temperature, making the fan works only if the temperature difference between the attic and the outdoor space is a bit high (over 10 degrees for example).
And in many cases, depending on where you live, the season, and on the area of the attic, the attic fan doesn’t need to run on full speed except for extremely hot or cold days.
This means that the actual numbers might be lower than this.
Another thing to know that these numbers are based on certain attic fan models from known manufacturers like QuietCool and Jet Fan USA.
While some attic fans that you might find on Amazon or somewhere else from other brands might not be that efficient and might consume several times the amount of electricity a comparable QuietCool attic fan uses.
For example, the BROAN 349BR attic fan with the 1,000 CFM rating consumes around 440 Wh (0.44 kWh) per hour of operation, more than 15 times what the smart roof QuietCool attic fan consumes of around 26 Wh (0.026 kWh) per hour of operation to get around the same CFM.
In a month, assuming both operate for 24 hours a day, then the BROAN attic fan consumes around 327 kWh, while the QuietCool attic fan consumes around 19 kWh.
And although the price of the more efficient fan might be two-to-three times the price of the least efficient one, but the savings on electricity bill can pay back the difference in few years.
How Much Power (Watts) Does an Attic Fan Use?
An attic fan draws anywhere between 30W to 300W, depending on the type (roof or gable), the manufacturer, the size or rating, and the speed you put it on since many attic fans have multi-speed settings.
As mentioned earlier, attic fans from brands are less efficient and consume more watts than 300W even for the small attic fan sizes with around 1,000 CFM.
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How Much Does it Cost to Run an Attic Fan?
The cost of running an attic fan with the rating of 30-300 Watt is around $2.46 – $24.6 per month based on the average electricity rate of around 11 cents/kWh, and assuming that it runs 24 hours a day for the whole month.
Note that electricity companies charge different rates based on the location and many other factors, and in some states like California for example, you pay 22 cents/kWh, which means that the cost of running the attic fan there is double the previous calculation, around $5 – $50 a month.
These are estimates based on running the attic fan at full speed, 24 hours a day, 31 days a month, which means that they are at the upper end of the spectrum.
But the exact cost changes based on the actual rating of the fan, the type (roof or gable), the actual number of hours it runs per day, and the speed at which it runs.
And for one of the lower efficiency attic fans, then the cost might be around $36 to get the 1,000-1,2000 CFM that you would get with the QuietCool smart roof attic fan that costs around $2.46 and gives around the same CFM volume. (enough for a small-medium size house of around 2300 s.f. attic).
While to get around 1,600 CFM for a larger home of around 3,000+ s.f. attic, then the cost might be around $70 or more per month.
Cheap Attic Fans vs. Efficient Attic Fans
The efficient attic fan in the previous example might cost around $400 to buy, while the lower-efficiency one costs around $120 to purchase.
The cost of installation would be almost the same.
That’s around $280 difference in order to get the efficient one. Is it worth it?
Considering the numbers above based on the electricity rates of 11 cents/kWh, then running the efficient attic fan would save you around $30+ per month, assuming that you run it 24 hours a day all year around.
That means that in only ten months, you would make back the difference you paid, and then you start saving around $30 per month.
Assuming that you run the attic fan only twelve hours a day, then you save around $15 a month, and you would need around only 19 months to pay back the difference.
Do Attic Fans Lower Electric Bill?
Attic fans might help you lower your electric bill during the summer as they might help keep the attic a bit cooler, preventing it from heating up the house due to the heat transfer through the attic floor and the floor just below it, which helps in lowering the AC bill.
But for winter, it is a bit different, because you need to keep the heat inside the house, and the attic fan will work on replacing the hot air in teh attic with a cooler one in order to prevent the moisture from damaging the roof and the attic walls due to the temperature difference between the hot attic and the cold outside environment.
In this case, the attic fan will not lower the electric bill, but it is meant to protect the roof and the attic from moisture and lower the home maintenance bill instead by paying a little for the electricity to run the attic fan itself.
But to keep the heat in the house and lower your heating bills, then you need to make sure that the attic floor has a good insulation that prevents limits the heat exchange with the rooms just below it.
Attic Fans vs. Whole House Fans
Attic fans are intended to keep the attic temperature close to the outside temperature in winter and protect the house from damages caused by moisture, and in summer, they can help in lowering the cooling bills slightly as they extract the hot air from the attic.
While that might help lower the AC costs during summer, but it does not work as a substitute to the AC or other cooling systems, especially in relatively hot areas.
Whole house fans on the other hand, work on keeping the whole house a bit cooler by circulating the air and extracting the hot air from the attic to the outside environment, and replacing it with cooler air from the windows in the different rooms, and might serve as a cheaper alternative to the AC.
(Courtesy of QuietCoolSystems.com)
Are Attic Fans Worth it?
Attic fans are worth the investment as they can help you lower your maintenance costs during winter by protecting the attic and the roof from the damages caused by the moisture buildup, and they could save on the cooling bills during summer by extracting the hot air from the attic.
To make attic fans worth the money, it is recommended to invest in installing an energy efficient attic fan that would save you on the electricity costs on the long run instead of buying a cheap one that uses a lot of electricity.
Are Solar Attic Fans Worth it?
Solar-powered or hybrid attic fans can save on the running costs by reducing the amount of energy you take from the utility, but they usually come at a higher price, and they might be more fit to smaller houses.
If you are installing an attic fan from the scratch, or if you are replacing a small, inefficient attic fan with an efficient one, then a good solar attic fan like the ones created by QuietCool might be worth the investment.
But if your attic fan is already efficient like the smart attic fans by QuietCool, then replacing it with a solar-powered one might not be worth the investment as it would take up to 10 or more years to pay itself back, depending on the electricity rates. The higher the rates, the faster it will pay itself back.
However, in some places, it might help you get some related tax incentives or cuts.
Conclusion – An Attic Fan Can Be a Money Saver
Attic fans can save you money on the maintenance bills in winter and on the electricity bill during the summer, but to maximize your savings, you need to invest in the right attic fan based on the following:
- The rated CFM based on your house’s needs.
- The type of the fan.
- The power rating and how energy efficient it is.
- If it comes with a thermostat.
- Does it come with multi-speed settings.
- Can it be controlled remotely (more about convenience).
- Does it come with a solar panel if the electricity rates are high.
If you are confused and need help in making a decision, you may consider contacting a professional in ventilation and attic fans in order to help you out make an educated decision.
And if you still need any help regarding this topic and regarding the attic fans electricity use, then please, feel free to ask me in the comments’ section below, and I will do my best to help you out 🙂
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