After using the whole house fan for a couple months now during the hottest part of the summer, there are distinct pros and cons associated with it. I’ll go through the pros first:
- Big-time energy savings…which is reducing the impact on the environment.
- During the course of a day, if the air conditioner is used solely to maintain a 75-degree temperature in the house, it will likely use 40,000 watts, or 40kWh of electricity. This is a conservative estimate, expecting the central air to be on for 20 hours a day, using 2000 watts of energy every hour.
- This compares to a whole house fan on low setting, running for 12 hours a day, using 528 watts, or 0.528 kWh. To maintain the 75-degree temperature, even if the central air was used for 2 hours in the afternoon which is , the combined energy for the day would be 4528 watts, or 4.528kWh of electricity. This is 9 times less the amount of energy when central air conditioning is only used.
- I ran several tests that maintained my home’s temperature at 75 degrees for 24 hours. The results are displayed in this visualization. One group of data included using only central air, and the other group included using central air and the whole house fan. When comparing tests during a day with similar temperature patterns, it was determined that the inclusion of a whole house fan reduced energy usage by nearly 880%, or 8.8 times less energy than solely relying on central air to cool the house.
- If you like to sleep in cool temperatures, a whole house fan will guarantee better sleep at night compared to relying on the passive cooling of open windows or an air conditioner. I’ve had no nights where I’ve gone to sleep in a warm bedroom, and I’ve slept better as a result.
- Given electricity rates reported by the Department of Energy of ~11 cents/kWh, the above example would cost $4.40 per day if using only central air conditioning. When using a whole house fan, this is reduced to $0.45 per day. If this occurs 60 times during the summer, you’ve saved over $235.00 in one summer.
- Electricity rates are increasing according to these official Department of Energy statistics, more than doubling over the past 20 years. If we extrapolate these rate increases, then the savings 10 years from now would accumulate to over 3000 dollars, paying for the whole house fan and then some.
- Cool home temperatures in the morning.
- After a full night of using the whole house fan, with outside temperatures dropping to 55-60 degrees, morning temperatures inside the house should be around 63-65 degrees, minimizing the need for air conditioning later in the day. This can be uncomfortable for some. For me, I just wear sweatpants and sweatshirt in the morning until the house warms.
- In order for the whole house fan to work correctly, several windows need to be open at night for cool air to circulate through the house. If you have a one-story house, this can pose a security problem. My suggestion is to leave windows open in your bedroom and in a part of the house that is secure or difficult to access from the outside. In a two-story house, there should be no problem.