Setback Thermostats-Can they save you $$?

While some homeowners could save money, others might end up spending more energy dollars by setting the temperature down temporarily.  Every degree you reduce your constant thermostat setting, and leave it there, will save you energy dollars.  But moving it up and down continually could cost you more in the long run, depending on the type of heating and cooling system you have.

Use the information below to see how your heating system would be affected by a nighttime temperature setback.    

Electric furnace (with or without an air conditioner)
 Using a setback thermostat is an efficient way to operate this system. Setting the thermostat temperature back at night   will save you energy dollars.  A fan blows air over hot, electric elements distributing heat throughout duct work.  To increase efficiency and reduce costs it is recommended to replace the air conditioner with an air-to-air heat    pump or install a geothermal heat pump.

Fossil fueled furnace (with or without an air conditioner)
Using a setback thermostat is an efficient way to operate this system. Setting the thermostat temperature back at night will save you energy dollars.  Uses propane gas, natural gas, or fuel oil.   A chamber is heated by burning the gas and the fan blows air over the chamber distributing the warmed air throughout the home’s duct work. To increase efficiency and reduce costs, we recommend you replace the air conditioner with an air-to-air heat pump or install a geothermal heat pump. 

Hot water heat (electric, propane, or natural gas)
Using a setback thermostat will probably be fine, but it may take longer to regain the normal set point than it would with a forced air system.   Often it is used to circulate hot water through pipes under floors in the home or to radiators. 

Geothermal (ground source) heat pump with electric auxiliary heat.  

A setback thermostat is not an economical solution for this system during the heating season, although it is fine during the cooling season.  Most efficient whole house heating system on the market.  Auxiliary electric resistance heat assists when temperature falls 2 degrees below temperature set point, and uses 4 to 6 times more energy than the geothermal heat pump alone.  Reducing the temperature more than 2 degrees and then raising it again in the morning will cause the resistance auxiliary heat to operate to catch up.
 Constant thermostat temperature setting recommended.    

 
Air-to-air heat pump with electric auxiliary heat
A setback thermostat is not an economical solution for this system during the heating season, although it is fine during the cooling season.  Auxiliary resistant heat automatically starts when inside temperature falls 2 degrees below temperature set point, and uses 4 to 8 times more energy than the air-to-air heat pump alone.  Reducing the temperature more than 2 degrees and then raising it again in the morning will cause the resistance auxiliary heat to operate to catch up.  Constant thermostat temperature setting recommended.

Air-to-air heat pump with fossil fuel auxiliary heat
 A setback thermostat is not an efficient solution for operating this system during the heating season.  During the cooling season it is fine.   The air-to-air heat pump will provide home’s heat until the outside temperature falls low enough to activate the fossil fueled (gas or fuel oil) furnace.  That furnace will operate and the heat pump shuts off. If the inside temperature, as set by those living in the home, is not reached in a set time, or if the inside temperature keeps falling, the heat pump automatically shuts off and the fossil fueled system takes over. 
If a nighttime temperature setback of more than 2 degrees occurs, the next morning when the temperature is increased the backup furnace will automatically operate. The heat pump will not operate until set point is reached and maintaining a temperature is all the system has to do.  Catch-up temperatures are more costly operating on fossil fuel than using the heat pump. Constant thermostat temperature setting recommended and utilize heat pump to its fullest.     

 There are setback thermostats made specifically for heat pump systems. They do not automatically bring on the auxiliary heat when trying to increase the home’s temperature after an extended setback. The thermostats are more costly and should be installed by a qualified heating contractor. Recovery time will be longer than using the auxiliary heat, and may not even be possible. The heat pump may not be able to supply enough heat by itself during extremely cold outside temperatures. Contact your heating installer for more information.