Save Energy — Thermostat

The thermostat is that unnoticed object on the wall that decides when heating or cooling should come on, thus impacting nearly half the cost of you utilities. Can any small device have a greater influence on energy use? If you control your thermostat, then you control your heating and cooling.

Your Home Energy Living Plan

  • Set winter temperature at lowest comfortable value.
  • Set summer temperature at highest comfortable value.
  • Set temperature, lower in winter and higher in summer, when home is empty for more than a few hours.
  • Set temperature lower in winter at night.
  • If you have a heat pump, never override to emergency/backup heat.
Impact of Your Energy Saving Actions

Since nearly half of your utility bill is for heating and cooling, then limiting the time the equipment runs will save energy. Spending time to find the best settings is worth the effort. If you have an old thermostat with a single setpoint for both heating and cooling, then you should consider replacing the thermostat. Thermostats costing more than $100 only provide the convenience of programmable setpoints over less expensive models. You can spend less than $100 on a thermostat and manually adjust the setpoint when needed.

How Energy is Lost

The thermostat tells your heating and/or cooling system to come on and when to turn off. If the thermostat thinks you need heat then the furnace comes on. If the thermostat thinks you need cooling, then the air conditioner comes on. This happens automatically. If the timing coincides with your needs all is right. If your not home or you really do not need heating or cooling, you get it anyway.

Thermostat Characteristics

The thermostat has a setting called setpoint. You determine the setpoint. The thermostat compares the actual temperature to that setting. In winter, when the actual temperature drops below the setpoint (temperature must fall a degree or so depending on manufacturer) then the thermostat allows the furnace to come on. The furnace raises the temperature of the air. When the temperature rises above the setpoint, plus a small amount, then the thermostat turns off the furnace. The actual temperature will fall due to heat loss and the cycle starts again. In the summer, the opposite happens. When the actual temperature rises above the setpoint, then the thermostat allows the air conditioner to start. The air conditioner will operate until the temperature drops below the setpoint.

The setpoint on older thermostats must be changed by you every season. Modern thermostats have a separate summer and winter setpoints. Modern thermostats save energy only by providing flexibility within its programming. Some thermostats allow you to set the setpoints for an entire week including any setbacks.

Energy Solutions Explained

You are the master of your domain. You must decide the indoor temperature that is comfortable for you and your family. Try different settings in winter and in summer. In the winter try settings when it is very cold and when it is not so cold. In the dead of winter, windows and walls become cold. Radiant losses are high and a higher setpoint is necessary to compensate. When cold temperatures are not so cold, then the setpoint can be lowered.

Do the same in the summer. In humid areas or during high humidity times, a higher setpoint will increase the humidity in your home. Find the setpoint that is acceptable during hot dry periods and wet warm periods.

Changing the setpoint at night or when you are not home is called setback. You may find many articles arguing the significance of setback. The theory is to let your home cool in the winter or warm in the summer when the normal setting are not needed. The drawback is that heating or cooling run longer to return the temperature to normal levels.

The reduction in runtime of equipment during setback must be greater than the additional runtime of equipment to return to normal setpoints. Since equipment efficiencies and outside temperatures vary, the is a difficult calculation. Your best approach would be to try different times and temperature for setback and compare your utility bills. Generally a setback for more than a few hours in the winter will save energy. Since summer nighttime heat gain is very low, summer setback has no affect. However, if nobody is home during the day, setback even in summer can save energy.

New thermostats have a clock which can allow for setpoints at different times. However any thermostat can be manually changed. Thermostats are low voltage (24 volts or less) and can be replaced by a cautious homeowner. However mistakes can easily occur (like the wires falling behind the wall). A heating/cooling contractor should be used to replace the thermostat.

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