Programmable Thermostats with Heat Pumps, Steam heat and Radiant floor heating

Recently J.D. at GetRichSlowly wrote an article questioning  Do Programmable Thermostats Really Save Money?  J.D. pointed out that while programmable thermostats can save you energy they often don't because people don't use them properly.   That is true.   A programmable thermostat is basically just a timer that automatically turns your heat on and off.    The real savings comes from setting the thermostat properly.

One other concern with programmable thermostats that many people may not be aware of is that they don't work well with all styles of heat.   The Energysavers.gov website from the Department of Energy points out that programmable thermostats have "limitations" when used with heat pumps, electric resistance heating, steam heating and radiant floor heating.

If you have heat pumps, electric resistance heating, steam heating and radiant floor heating then you need to make sure you use a thermostat that is specifically designed for use with your style of heating.

Each of these heating systems operates differently than a plain forced air furnace.   The normal programmable thermostats are basically used to create a setback so that the heat is turned down when you're asleep or away from the home.   However this can fail to work efficiently and backfire when using heat pumps, electrical resistance, steam heat or radiant floor heating.   A standard programmable thermostat can end up costing you money if used with heat pumps, electric resistance heating, steam heating or radiant floor heating.

Heres some quotes form the DoE Energysavers website on how each of the forms of heat may not work well with a standard programmable thermostat: 

Heat Pumps

"Programmable thermostats are generally not recommended for heat pumps. In its cooling mode, a heat pump operates like an air conditioner, so turning up the thermostat (either manually or with a programmable thermostat) will save energy and money. But when a heat pump is in its heating mode, setting back its thermostat can cause the unit to operate inefficiently,..."

Electric resistance

"Electric resistance systems, such as electric baseboard heating, require thermostats capable of directly controlling 120-volt or 240-volt circuits. Only a few companies manufacture line-voltage programmable thermostats."

Steam or Radiant floor heat 

"For steam heating and radiant floor heating systems, the problem is their slow response time: both types of systems may have a response time of several hours. This leads some people to suggest that setback is inappropriate for these systems."


If you have any of these heating systems then you either just stick with your manual thermostat or you could  look for a specialized programmable thermostat that  is designed to work with your heating system.  If you don't know for sure what heating system you have then you should definitely find that out before you attempt to change your thermostat.