Which is cheaper to run, a whole house fan or my central air?

Question

Which is cheaper to run, a whole house fan or my central air?

Answer 1

Speaking strictly in terms of electricity use, a whole house fan as it runs on 110-120 volts as opposed to a 220 volt AC.  A whole house fan does not cool unless the outside air it is drawing into the house is cooler than the air inside the house.  Ceiling fans are said to lower your electric bill by up to 20%.  

Answer 2

Well, it depends on whether simply saving money, or having comfort, or both, is your main goal.

But there is a compromise solution.

1) You must weather-seal and insulate your home the best you can.

2) If you can afford to have an HRV installed, you can save a fair bit of money on the needed ventilation (especially in winter) that way.

and:

3) Let us assume that you run your A/C to the max, from, say, 11AM to 2Pm or 3PM.  You will have cooled off whole the house.  If you have a basement, you now have a lake of cold air down there.  (If you have no basement, this plan is not as effective, but it will still help.)

Turn the A/C off by cranking up the t-stat to, say, 80.  Now run your whole house fan.  The cold air from below is brought up, and the warm air goes down, and you will find that the house will stay tolerable untill maybe 5PM or even 7PM.  

If we assume that it is now cooler outside than inside, now is the time to bring in cold outside air (... By using open windows, and window fans that suck cool air in one side of the house, and exhaust hot stale air out the other side.).  

If it is not cooler outside, run the A/C again for about 2 hours, until, say 9PM.  Turn it off, and revert to the fan again.  

When you go to bed, at say, 10:30 pm, you can perhaps even turn off the whole house fan.  

Assume someone gets up early, around 5AM, you will find it quite cool outside now.  Bring in that cool air with open windows, and window fans.  Close up tight around 7:30AM, and you should be comfy, perhaps without even needing to run the house fan until 9AM.

Then you turn on the house fan, and run that until 11AM or so.  You then repeat the process.  

By minimizing A/C use, and Fan use, to only when needed, you save money, and you maximize comfort.

Another VIP thing:  The dryer the air, the cooler and more comfortable it is.  The more humid the air, the more heat it contains, and the hotter, and muggier it is.  A cheap $150 dehumidifier, strategically placed, and run constanly, uses about the same power as a 100 watt bulb.  But it can make a home 20% more comfortable, and make the A/C's or the house fan's job much easier.