Heat Pump Thermostat: Add Efficiency to a Two-stage Heating System

Tom Kraeutler asks,

Do I need a heat pump thermostat? I have a two-stage heating system that switches from an electric heat pump to a gas furnace when the outside temperature drops to 10 degrees or when the temperature differential (set/actual) is more than a few degrees. Is it worth it to program my existing thermostat to a lower setting during the day if the system has to switch to gas to bring the house back to a comfortable temperature for the evening? And isn’t a programmable thermostat doing more harm than good in this case (for my wallet and for the environment) by forcing the expensive gas backup system to come on?

Our Answer

Good question, and this does sound like a job for a heat pump thermostat. You would be correct about the issues around programming a thermostat if you were using a normal, run-of-the-mill, clock setback thermostat, because bouncing the temperature up and down would cause your gas backup furnace to come on to keep up with the demand for heat.
Instead, the solution is to purchase a clock thermostat that is specifically designed for a heat pump. The difference is that a heat pump setback thermostat moves the heat up and down slowly, so as not to exceed the differential setting that cues the backup gas system to come on. Heat pump thermostats are a little difficult to find sometimes, but if you contact a local professional HVAC supply company, order online or check with the heat pump manufacturer, I’m certain that a heat pump thermostat can be secured.