A programmable thermostat lets you preset temperatures for different times of the day, so air-conditioning is working only when you are home. The least expensive thermostat models ($30) let you set four cycles that, unless manually overridden, repeat every day. Higher-priced models ($50 and up) allow you to create settings for each weekday and for each weekend day.
These thermostats come with complete directions and are easy to install. Just remove the old thermostat, unscrewing the wire leads attached to the terminals on the back. Reattach those wires to the terminals on the new model (in a system with separate A/C and heating units there may be four leads on the back, two for each unit). AA batteries maintain the settings if the power ever goes off.
If you have central air, set your thermostat above 78 degrees (all temperatures cited here are in degrees Fahrenheit). You’ll save 5 to 8 percent on cooling costs with each degree above that mark. For a typical household, setting the thermostat at 80 degrees saves 10 to 15 percent; raising it to 85 degrees will save 35 to 55 percent.
When you leave home for more than one hour, set the thermostat to 85 or 90 degrees. Reset it upon your return, and the room will cool down in only 15 minutes. The system will use less energy during the cool-down period than if you had left it running at a lower setting while you were out.
Typical air-conditioning settings for a programmable thermostat at different times of day:
6 a.m. to 9 a.m. = 75 degrees
9 a.m. to 5:30 p.m. = 85-90 degrees
5:30 p.m. to 11 p.m. = 75 degrees
11 p.m. to 6 a.m. = 80 degrees
Tip 3: Use a Fan
A fan, which costs two to five cents per hour to operate, will make a room feel 4 to 6 degrees cooler. Also, a fan works well in tandem with an air conditioner because the dehumidifying action of the air conditioner provides drier air that the fan can then move around.
In frequently used rooms, install a ceiling fan (set it to spin counterclockwise in summer). You’ll save the most money by running the fan only when you’re in the room. A motion-detector switch (around $20), which turns the fan on when you enter a room and off when the room is empty, is a good addition. However, if you have pets that move in and out of the room, make sure the switch can be turned off manually. Otherwise, your pets can cause the fan to run while you’re away.
If nighttime temperatures drop into the 70s where you live, you might want to purchase a whole-house fan, which runs $300 to $600 installed. This type of unit goes in an upstairs ceiling, ideally in a central hall. When run at night with the windows open, the fan will pull cool air into the house as it vents hot air out through the attic. Most models are designed to slip in between joists for easy installation. Whole-house fans, which draw only as much power as a couple of lightbulbs, are usually outfitted with a variable-speed switch and/or timer. If you install one, be sure to get an insulated box to cover the portal in winter.
Tip 4: Practice “Texas Cool”
“Texas cool” is a morning and evening routine that takes advantage of cool outdoor temperatures at night and keeps the heat at bay as much as possible during daylight hours. It’s very simple to do: At night when the temperature drops, open windows and bring in cool air with window fans or a whole-house fan. As soon as the sun comes up or the air starts to heat up, shut the windows and shades and keep doors closed.
Tip 5: Use Sunblockers
As much as 20 percent of summer heat enters your home as sunlight shining through windows. To cut “solar gain,” add curtains or blinds to rooms that get direct sun and draw them in daylight hours. With the shades drawn, a well-insulated house will gain only 1 degree per hour when outdoor temperatures are above 85 degrees.
Pay special attention to west-facing rooms late in the day. Shades and blinds to consider include roller shades (the least expensive option), venetian-type micro-blinds, reflective curtains and insulated curtains (the most expensive, at $100 per window). Two exterior options are to install awnings or plant shade trees.