If you turn down the heat when you're sleeping, you'll use less fuel

09:30 AM EST on Monday, November 14, 2005

BY TIMOTHY C. BARMANN
Journal Staff Writer

Part six of a series

Turn the heat down before you leave the house.

It's an old adage many of us try to follow. But does it really cut heating costs?

Energy experts say yes. Turning back a thermostat is an effective way of trimming heating bills by 10 percent a year, or more.

But doing so is easy to forget. And it's unpleasant to come home to a cold house.

Both of those issues are easily fixed by installing a programmable thermostat.

This device is essentially a fancy switch that turns the heat on and off, depending on the inside room temperature -- just as the old manual type does.

But a programmable thermostat can also be instructed to automatically turn down the heat at a specific time, and turn it up again later in the day.

Programmable thermostats can be used for most heating systems, but are not recommended for heat pumps.

Prices run from $40 on up, and the cost of the unit can be recouped in lower energy bills in just a few months.

"We really encourage people to get them," said Christina Kielich, a spokeswoman for the U.S. Department of Energy. "It's a really small investment for a big return."

For each degree a thermostat is turned down for an eight-hour period, heating costs are trimmed by 1 percent, according to the Energy Efficiency and Renewable Energy division of the energy department.

The agency has a calculator on its Web site that computes the savings and the pay-back period for various climates. It also lets you plug in specific rates for energy in your area.

For example, a Providence household that buys three programmable thermostats at $50 each will recoup that money in about seven months. A residential natural-gas heating customer who turns back the thermostat to 62 degrees at night from 70 degrees during the day would save $235 a year, according to the calculator. The savings with an oil boiler would be $248 a year. (See the link below to try it yourself.)

A programmable thermostat is fairly simple to install, involving little more than a screwdriver and some patience.

Journal photo illustration / Kris Craig

Programming them is simple, too. In general, you tell the thermostat what temperature you want the house to be at a specific time. The devices usually allow four temperature changes during a day.

For example, you might want the temperature to be 68 degrees at 7 a.m., when you wake up. At 8 a.m., when you leave for work, you may want the temperature to drop to 60 degrees. The thermostat can turn the temperature back up to 68 degrees when you arrive home at 6 p.m. And it can turn it back down to 62 degrees at 10 p.m., when you go to bed.

Some thermostats have the ability to figure out how long it takes your heating system to get up to temperature. That way, it knows precisely when to turn on the furnace or boiler so it is at the right temperature at the programmed time.

Some units keep a log of how often the heat was turned on during the day, during the week and during the whole season.

How low should you turn back the thermostat?

Kielich, the Energy Department spokeswoman, said to turn it down as low as you are comfortable with, but not below 55 degrees. Below that, you run the risk of freezing pipes.

A common misconception about turning down a thermostat is that the heating system works harder than normal to bring the temperature up, resulting in no savings.

The Energy Department says that theory has been dispelled by years of research.

The amount of fuel needed to reheat the house is about equal to the fuel saved as the building drops to the lower temperature, according to the Energy Department.

So, the longer your house remains at the lower temperature, the more energy you save.

-- Timothy C. Barmann covers energy issues, utilities and technology. He can be reached at tbarmann@projo.com

Programmable-thermostat savings calculator

The calculator is a downloadable Excel spreadsheet

at: http://www.energystar.gov/ia/business/bulk_purchasing/bpsavings_calc/CalculatorProgrammableThermostat.xls

Use these Rhode Island energy rates: electricity, $0.141 per kilowatt-hour; gas, $1.74 per therm; and heating oil, $2.459 per gallon.

More details about programmable thermostats are available at:

http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12720