Dog Days Are Here: Keep Cool for Less


Aug 12, 2001 (Updated Aug 31, 2001)


Popular Products in Air Conditioners
The Bottom Line Keeping cool during the summer does not have to cost a fortune. Here are some tips for saving some of your air conditioning dollars.

With summer heat in full swing, the arrival of each month's electric bill is for some consumers as traumatic an occasion as an unplanned visit from the IRS. Sure, you might think, energy savings are possible, but doesn't that mean spending a lot of money to add insulation and "tighten up" a home? No. In fact, a study by the U.S. Government's Oak Ridge Laboratory even found that some of the most expensive measures people undertake to improve energy efficiency may not actually lower summer air conditioning bills a single cent. In contrast to this, many of the most effective and beneficial steps you can take to save money on cooling costs don't require any investment at all and don't even sacrifice your comfort.

1. With either window or central air units, make certain that the condenser coils on the outdoor side are not obstructed by plants, weeds, tall grass, or other items. An air conditioner needs a free flow of air all around it on its outdoor side because the heat it pumps out of your house has to be able to flow away. Obstructions will hold the heat near the unit and reduce its effectiveness, increasing its running time as it runs up your bill.

2. If possible locate window units on the north side of your home where direct sunlight is limited. If this isn't possible, locate them in a window which gets shade from a tree or another building during part of the day. Since the air conditioner has to transfer heat to the outdoors, it works better and more efficiently if it's kept as cool as possible. Again, just make certain that a unit is not within three feet of obstructions such as those described above.

3. If everyone is gone from your home during the day, raise the temperature on a central air conditioning unit at least three to five degrees. This will reduce power consumption and operating costs without letting the house get so warm that it takes forever to cool back off in the afternoon. If you raise the temperature five degrees and the a/c unit has no problem bringing the temperature down to a comfortable level in an hour or so, try bumping it up a degree or two more the next day. On the other hand, if the air conditioner labors away all evening and the house still feels too hot, don't raise the temperature quite as much when you leave the next morning.

3. If you currently keep your home cooler than 78 degrees, raise the thermostat to 78 and see if everyone remains comfortable. People who need the house kept at 72 or 74 to feel comfortable often simply need to change their habits: Wear lighter clothing, drink cool rather than warm beverages, close curtains and blinds as necessary to keep the sun from heating up rooms on the sunny side of your home.

4. If you use window air conditioners, make sure they are well-sealed into their windows. Many people leave big gaps around these units, letting in a lot of heat and humidity (as well as a lot of bugs). A very convenient way to fill in small gaps is with "rope caulk" which comes in rolls and has about the same consistency as modeling clay or Play-Dough. It requires no tools to use, and it's easy and clean to work with: You simply peel it off the roll and press it into small cracks to close off the flow of hot air.

5. Don't run washing machines, dryers or dishwashers, and avoid heavy baking and cooking, during the hot hours of the day. Adding a bunch of extra heat during the hot hours of the day will make your a/c work overtime to cool your home -- and may make your house uncomfortable if the unit can't ultimately cope with all of the heat you are creating.

6. Use a thermometer to check your thermostat's accuracy if you have central air, and if you have a window unit or units use a thermometer to calibrate the built in thermostat. If you set your central air at 78 but the house is actually being maintained at 74, you aren't saving as much energy as you thought you were. Similarly, window units are usually equipped only with a dial that is calibrated in numbers, such as 1 to 10, which don't correspond to actual temperatures. In this case use a thermometer placed somewhere in the room (not directly in front of the unit or in the direct flow of air coming from it) to get a fix on the room temperature. Experiment with different dial settings until you arrive at the one that will hold the room at 78 degrees, and then leave the thermostat set there. When first turning the unit on after it has been off for a while, it is not necessary to reduce the thermostat beyond this "preset" point, as it will not cool the room any more quickly.

7. Consider buying a computerized thermostat for a central air unit, or timer(s) for window unit(s). Day to day activities are often hectic, and air conditioners are frequently left on during long periods when no one is at home, or are set to very cool temperatures even though a house is empty. If you have central air, a computerized thermostat can automatically bump the temperature up after everyone leaves for work or school, and then bring it back down so the house is already cool when you get home. The temperature can also be raised a few degrees during the night and then reduced again before morning.

Window air conditioner users can achieve the same savings by the use of appliance timers which switch the unit(s) off in the morning and back on an hour or two before people return home. Not only that, because most timers have several different on/off times you can preset during each 24 hour period, you can also use them to automatically save energy at night by cycling the unit(s) off for a couple of hours while everyone sleeps. Again, the units can be set to turn back on early enough that your home is again pleasantly cool by the time everyone awakes.

8. Use exhaust fans in bathrooms and kitchens to remove overheated or excessively damp air, but be careful to turn them back off after they've done their job. They'll help you save energy if used carefully by keeping the hot or damp air from moving to the rest of the house and making your a/c run more. But if you leave them on too long they'll suck cooled air out of your house and throw it away outdoors.

9. When replacing your air conditioner -- window or central -- consider a unit with a high EER rating (for window units) or SEER rating (for central units). For both types of units, the higher the number of the rating, the more efficient the unit.

However, according to an exhaustive study undertaken by the U.S. Department of Energy, it does not generally pay to get rid of a properly functioning air conditioner merely to upgrade its efficiency. That study ("The Oklahoma Field Test: Air-Conditioning Electricity Savings From Standard Energy Conservation Measures, Radiant Barriers, and High-Efficiency Window Air Conditioners," Mark P. Ternes and William P. Levins. Office of Scientific and Technical Information P.O. Box 62, Oak Ridge, TN 37883) found that the average savings for upgrading an air conditioner to a high-efficiency model was less than $50 per year. Clearly this level of savings makes it worth your while to buy the most efficient model you can get when you replace a unit which is defective and no longer repairable. But it's probably not enough to make you junk an older unit which is doing the job.

The same study found that such standard energy conservation measures as adding attic insulation, improving or adding storm windows, etc., had little or no effect on cooling costs. As mentioned above, it pays to close up gaping holes around your air conditioner itself, but don't spend a lot of money replacing windows or adding tons of insulation. The study's authors speculate that this may be due to the fact that "looser" houses actually ventilate better during the summer and do not remain hot for as many hours after the sun sets.

10. If you routinely use only a small area of your home for long periods of time, consider buying a window unit for that area so you can shut off the central unit or at least increase its temperature setting. Window units these days are very efficient and produce a lot of cooling for very little energy. Running an efficient (EER of 10) 8,000 btu window unit 12 hours a day for an entire month would cost about $23.90 in electricity if you pay the national average electric rate of about 8.3 cents per kilowatt hour. A central unit cooling the whole house for the same number of hours would consume four to five times as much power.

It is not normally a good idea with central air, however, to close off unused rooms and shut a lot of registers. If adequate airflow is not maintained across the unit's evaporator coil, it can become covered with ice, reducing its efficiency drastically. In extreme cases of "icing up" it can even break, resulting in a several hundred dollar repair. Closing a few registers is okay, but the problem can occur if many are closed simultaneously, as would happen if someone wanted to close off entire rooms.

11. If an air conditioner repeatedly needs to be recharged with refrigerant ("Freon"), insist that the serviceperson find the leak and fix it. During periods of hot weather, busy service people sometimes simply recharge a unit and move on to the next customer, not realizing that it had been recharged a few months before, possibly by a different technician. Not only is the leaking refrigerant a possible environmental hazard, it means that most of the time your unit is running somewhat low on refrigerant, meaning it runs much longer to produce the needed cooling.

12. "Energy Saver" settings on window air conditioners cycle the fan with the compressor, meaning that the unit shuts entirely off when the compressor stops, not leaving the air circulating fan running as it will do in the non-Energy Saver mode. This setting is advantageous on days when the primary purpose for running air conditioning is humidity removal. However, on really hot days, the energy saver setting can drastically reduce comfort by not keeping air moving in the room. If this causes you to set the unit to a colder temperature, the energy saver is not really saving you any energy, and could in fact be causing you to use more. This is because on a typical window a/c unit the fan uses only about 10 percent of the total power consumed by the unit. The other 90 percent is used by the compressor.

13. Similarly, running the unit in "low cool" or "medium cool" mode rather than high saves very little energy, since those settings only control the speed of the fan, which uses little energy. If the compressor runs longer to maintain a comfortable temperature because the fan speed is set too low, the unit will actually consume more total energy than it would have if it were set to a higher speed. Low cool is best, however, for dehumidifying a room; on damp days that aren't too hot, low cool can be your best bet.

14. Replace your incandescent light bulbs with compact fluorescents (CFLs). A 100 watt incandescent bulb is essentially a 100 watt heater which is adding approximately 341 btu/hour of heat to your home. If you have ten of them on at various points in your home in the evening, they are adding over 3,400 btu/hour of heat to your house, which is as much as running a portable electric heater in your house -- at the same time you're trying to cool it. A CFL rated at 25 watts will produce the same amount of light as a 100 watt incandescent but only a fourth of the heat -- and they consume a fourth of the power. In this way, they not only save on cooling costs but keep on saving year round as you spend less on lighting, cutting the energy you spend on lighting by 75 percent.

While CFLs cost more than incandescent bulbs (about $10 - $12 apiece) they are a good investment because they last 10,000 hours or more. If every American household replaced just one 100 watt incandescent bulb with a 25 watt CFL, our nation's electricity demand would drop by 11,250 megawatts, which is equivalent to the power produced by more than five large power plants, saving not only energy but reducing pollution. This does not even count the energy that would be saved through the reduction in air conditioner operation in those homes during summer months.

You don't have to be a handyperson or a technician to save energy, and you don't have to sacrifice your comfort either. Just following these tips and using some common sense can help you get through a hot summer without dreading the arrival of your electric bill.

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