Saturday, July 19, 2008

Thermostat Know How

You’ll save -- energy -- and money if you lower the temperature setting on your central furnace or heat pump thermostat.

Selecting the proper temperatures throughout the day and night can be a bit confusing. You want to balance comfort with energy and dollar savings. However, it is surprising how comfortable you can be at a lower indoor temperature once you become accustomed to it. Thereafter, you find yourself uncomfortable at higher indoor temperatures that used to seem normal.

It actually does save energy overall if you lower the temperature setting on your central furnace or heat pump thermostat. The actual amount of dollar savings depends primarily on how low you set the thermostat, how long you have it set back, and to a lesser degree, your climate.

There are other advantages to lowering the thermostat during winter. A lower house temperature requires less moisture indoors to keep the indoor air at a given relative humidity level. And, your furnace or heat pump runs less at a lower indoor temperature, meaning the equipment will last longer and need fewer repairs.

If you look at setback savings charts, don’t be confused by the fact that the percentage savings are actually higher in milder climates than in colder ones. This is because the total amount of energy used to keep a house comfortably warm in a cold climate is much greater. This makes the base number larger in cold climates so the percentage savings are less even though the dollar savings are greater.

It is a myth that it takes as much energy to reheat a house, in the morning for example, as was saved during the temperature setback period overnight. The amount of heat a house loses through its walls, ceilings and floors is directly proportional to the difference between the indoor and the outdoor






temperatures. Air leakage into and out of your house also increases with larger temperature differences.

When the indoor temperature is set lower, the indoor-to-outdoor temperature difference is smaller so less heat is lost from your house. During the summer, the same is true in reverse. If less heat is lost from your house, your furnace has to use less gas, oil or electricity to create the heat to replace it. The amount of heat used to reheat the house, therefore, is less than the amount saved over the temperature setback period.

The only time a temperature setback may not be wise is if you have a heat pump with backup electric resistance heat and an old thermostat. When it is time to reheat the house and you set the thermostat higher again, the expensive backup electric resistance heater may come on. For a long eight-hour setback, you will likely still save overall, but not for just a short setback of a few hours.

If you have a heat pump, install a special setback thermostat designed for it. These heat pump thermostats have electronic circuitry to keep the backup resistance heating elements off after the setback period. My own heat pump thermostat works this way and it also allows me to block out the resistance heating when the outdoor temperature is above a certain temperature. I have mine set at 20 degrees.

There is not a “best” thermostat setting for all homes and climates. The lower you set it, the greater the overall savings will be. The amount of savings per degree for each nighttime eight-hour setback period ranges from 1 percent to 3 percent. Since many people are also gone to work during the daytime, the temperature can be set lower for about 16 hours per day. Unless there are health problems in your family, 62 degrees is comfortable if you are wearing long sleeves or a sweater.

In moderate climates, let your comfort dictate how low you initially set the furnace or heat pump thermostat. As you get used to the lower temperatures and wear a sweater, you will be able to gradually lower it more. In colder climates, excessive window condensation often limits how low the indoor temperature can be set. To set the temperature lower, you will have to reduce the indoor humidity level.

Use smaller room-heating appliances with built-in thermostats to keep just a room or two warmer if you like. Reiker) makes ceiling fans with a built-in heater and remote digital thermostat. honeywell digital thermostats makes a very efficient portable heat pump with a thermostat and remote control. Many inexpensive electric space heaters also have thermostats for zone heating.

3 comments:

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