Energy Conservation Myths

Almost everyone agrees that it's a good idea to conserve energy, despite differences about how much comfort and convenience to give up in the process. But energy conservation rules can be confusing- and muddled even more by not-so-true truisms that seem to save energy but actually waste it. Here's a look at a few of these energy myths.

* Turning a thermostat to its lowest setting makes a room cool down faster. Not true- or for setting a thermostat higher to get quicker heating, either. Almost all airconditioners and furnaces work at a constant rate. To produce more they have to run longer. There is no "faster" mode for cooling or heating in a hurry. It will take the same time for a warm room to cool to 72 degrees whether the thermostat is set at 72 or 62. The downside of this myth is that people forget to return the thermostat to a normal setting- until it's too cold or too hot and a lot of energy has been wasted.

* It takes more energy for an airconditioner or furnace to recover from a thermostat setback than it does to leave the setting at a comfortable level. Not true. It takes less energy to cool or warm a room in the morning than it does to maintain temperature through the night. The Department of Energy says, "The fuel required to reheat a building to a comfortable temperature is roughly equal to the fuel saved as the building drops to the lower temperature." The up and down sequence is a wash, but you save energy every minute that the building (or part of it) remains at the lower temperature. It takes more time to cool down or warm up the house. But a little extra run time can't dent substantial daylong or nightlong savings. One good rule of thumb: You save about one percent of cooling or heating costs for every degree you do without over eight hours. Set back the thermostat downstairs ten degrees while you're upstairs overnight, and you'll save 10-15 percent of heating or cooling costs- and without compromising comfort, according to the National Association of Homebuilders. The only equipment you need to save so much is a programmable thermostat- probably the best energy-saving investment of all time. Of course, it also helps to have zoned heating and cooling systems, each with its own thermostat controlling a different area of the house.

* Leaving lights on all the time uses less energy than turning them on and off when they're used. Not true. Both incandescents and fluorescents use more energy left on all the time than they do turned on and off as needed. Some argue this can't be true, at least for fluorescents, because they draw an initial current five times greater than the operating current. But the starting surge of a rapid-start lamp lasts only 1/120th of a second. If you turn the lamp off for only a few seconds you'll still save more energy that it takes to start the lamp again. An energy study by the University of Oregon says that many people developed the habit of leaving lights on when fluorescents first came into use in the 1950s. But modern fluorescents are more durable and efficient than they were then, and save energy long term even though on-off cycling does take a toll. It seems unlikely, but here's the math. A standard rapid-start fluorescent left on all the time burns for 38,000 hours or about 4.3 years. Limited by on-off switching to 12 hours a day it will burn for only 30,000 hours. That makes switching seem counterproductive. But the lamp burning only 12 hours a day will remain in service for 6.8 years. So in this example you cut operating energy consumption in half and reduce lamp replacement costs by 30 percent. Without all the math, just bear in mind that turning off lights always saves energy. You'll save even more changing to compact fluorescents, which are three to four times more efficient than incandescents and last about ten times as long.

* It uses less energy overall to boil water if you start with hot water from the tap. Not true- but sort of a trick question. That's because you'll use roughly the same amount of energy regardless of where the energy comes from. If you start with hot water, you've already used energy in the water heater to raise its temperature. If you use cold water from the tap you'll save the water heater component but use more on the stovetop. Water will certainly boil faster if you start with a supply from the hot tap, and even more so in a covered pot that helps prevent heat loss.