Whole house fans use 200 to 650 Watts of energy in an hour depending on their CFM rating. Likewise, it will cost an average of 2.6 to 9.1 cents an hour to run a whole house fan.
Here is the list of popular whole house fans and the energy they use;
|Model||CFM||Energy consumed||Cost per hour*|
|Tamarack Technologies HV1000 R38||1000||70 Watts per hour||0.91 cents|
|QuietCool QC CL-1500||1472||117 Watts per hour||1.521 cents|
|QuietCool QC CL-2250||2280||250 Watts per hour||3.250 cents|
|Cool Attic CX24DDWT||2985||150 Watts per hour||1.950 cents|
|QuietCool QC CL-3100||3126||320 Watts per hour||4.160 cents|
|QuietCool QC CL-4700||4505||591 Watts per hour||7.683 cents|
|QuietCool QC CL-5400||5024||649 Watts per hour||8.437 cents|
|QuietCool QC CL-6000||5665||769 Watts per hour||9.997 cents|
|QuietCool QC CL-7000||6924||1147 Watts per hour||14.911 cents|
* The cost per hour is calculated based on the average kilowatt per hour rate across the USA which is 13 cents.
As per the table, the Wattages of whole house fans range from 70 to 1147. However, the most popular choices are between 2000 to 5000 CFM, and so it is safe to assume that the energy consumption of whole house fans ranges from 200 to 650 Watts.
How to reduce the energy consumption of whole house fans?
Whole house fans only use a fraction of energy used by air conditioning equipment. However, their incorrect use can drive up your energy bills. Here are a few things to make sure that they run energy efficient;
Make sure the attic have proper ventilation
Having proper attic ventilation is very important for the efficient working of whole house fans. A thumb of rule is to leave 1 sq.ft of attic vetilation for every 750 CFM of the attic fan. This ofcourse means that the air should be able to flow through the vent without obstructions. The presence of nets and grills will obstruct air flow to some good extend. So in this case the required attic ventilation area is 25 to 50% more of what is mentioned above.
If proper attic ventilation is not provided the whole house fan won’t be able to push the hot air out into the environment. This will reduce the suction of hot air from the house, increase the load on the motor of the fan, and thus increases energy consumption. So for the energy efficient working of the fan it is important to leave your attic with enough ventilations.
Open enough windows and doors
Since whole house fans draw air from the outside it is important to keep some windows open during their operation. The suction power of these fans are so huge that they can create a negative pressure in the house. Keeping two or three windows open will make sure that the fan is able to draw in enough fresh air from the outside. Failure to draw air wil increase the load on the motor which will lead to more energy consumption and may be damage to the fan.
Install the fan in a central position
Whole house fans should be installed at a location which make them easy to draw air from all the rooms. The purpose of using a whole house fan is to cool the house by providing a cool air flow. If the fan is located very far from some rooms or at a corner of the house then it will have to work longer to cool the living spaces. This will mean more energy consumption. So to keep energy consumption to the minimum whole house fans should be installed at a centrak, open location of the house.
A comparison of the energy consumption of common household appliances to a whole house fan
|Appliance name||Energy consumption (Watt)|
|Whole house fan||700|
From the above table you can see that whole house fans do not consume as much energy as many appliances we use daily at home.