by Arnie Katz
Q: My builder recommends putting ceiling fans in every room to save on energy bills. Many of my friends have them and like them, but do they really save money? The builder wants to install seven fans at about $250 each, including installation costs. Can they really save me over $1750 in heating and cooling bills? My wife wants to put the money into landscaping. She says a couple of good shade trees will keep us cooler and are a lot prettier.
A: Hang on to that wife of yours-she's obviously smarter than most of the engineers I've run into lately. In theory, ceiling fans can save money on air conditioning bills. They can do this in two ways. The first way can happen in the spring and fall. When it's not too hot outside, you can sometimes use the fans to keep comfortable instead of turning on the AC. The fans use less energy than the AC, so you'll save a few bucks.
The second way is to use the fans during seriously hot weather. A fan blowing air on you can make you feel comfortable at a higher temperature. If, for instance, you normally keep the thermostat set at 76 o in the summer, you can probably set it up to 78 o or even 79 o and be just as comfortable — if you're sitting or standing in front of or under a fan.
Air blowing over your body increases the amount of evaporation from your skin, which is how we cool ourselves. In practice, unfortunately, most people don't use their ceiling fans in a way that actually saves them money. A study in Florida found that there was no difference in thermostat settings for people using fans and not using fans. If you don't turn up the thermostat, then the AC will run just as much, and you won't save a dime.
In fact, since the fans themselves use energy, it will actually cost you more! If you want to save money by using fans, the key thing to remember is that fans cool people. They don't cool air. They don't cool rooms. They do cool people. So run the fans only when there are people in the room.
In order to be economical, you have to think of the fans like you think of lights. Or, rather, like my grandmother thought of lights. You go into a room, you turn on the light (fan). You leave the room, you turn it off. Blowing air onto your living room carpet or onto your bed, when no people are there, will cool nothing except the dust mites. I go into houses all the time and find three or four or seven ceiling fans running. And folks actually believe they are saving energy.
If you entertain a lot, ceiling fans can definitely help keep a large crowd of people more comfortable, even if the air conditioner is having trouble keeping up with the load.
In theory, ceiling fans can also save energy in the winter. By reversing the direction of flow, the fans suck air up and push it around, theoretically pushing the warmer air at the top of the room down to where the people are. If it causes the air around the thermostat to stay warmer, then it will cause the heater to run less, which will save you money. To date, I've seen no research that demonstrates this actually happens in the real world.
If you do run the fans in winter, be sure to run them on the lowest speed. Remember that air flowing over your body will cool you off. In the summer, this can improve comfort. In the winter, it can just feel drafty, which can lead to cranking the thermostat up rather than down.
Another consideration is whether or not you are among the millions of people who regularly burn candles in your home. Air currents across a candle flame will make the fire flicker. Flickering flames often produce soot, which can deposit on walls, floors, carpets, appliances, TV screens, etc. As a rule, don't burn candles in a room with a fan on.
So, should you invest $1750 in ceiling fans? It depends on the whether-whether you think you and your family will operate them in a reasonable way. If you think you can train yourselves to run them only when people are present, ceiling fans can definitely enhance comfort. But if you think you're likely to turn them on in June and let them run till September, I think a few fine specimen shade trees will probably contribute more to the quality of both your life and your bank account.
The most optimistic estimates I've seen on energy savings from ceiling fans peg the air conditioning savings at about 15%, assuming people do raise the thermostat setting and only run the fans when people are in the room, and taking into account the cost of energy used by the fan itself. At current interest rates, the $1750 will cost you about $12 a month, or $144 a year, for thirty years on your mortgage.
In order to break even, your air conditioning bill needs to be $960 per year. If your bills are that high, you've got some major problems that ceiling fans aren't gonna solve, problems like inadequate or poorly installed insulation, leaky ducts, a poorly performing air conditioner, or a very leaky house. Obviously, if you buy lower cost fans, the numbers will look better, but don't forget it's unlikely for the fans to last for thirty years. The shade trees are looking better and better.