Why Does My Heat Pump Keep Running?

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A heat pump is a machine or device that transfers thermal energy from one location called the "source," which is at a lower temperature, to another location called the "sink" or heat sink which is at a higher temperature.¹  In the winter, a heat pump removes available heat from the air outside your home (yes, there is heat in cold outdoor air) and moves it indoors, providing an even, comfortable temperature level throughout your home. There are seldom any warm or cold spots such as those that exist when a gas furnace alone is used.  In the summer, it removes heat from inside your home and replaces it with cool air.

Heat pumps seem like they are running all the time because it actually is heating/cooling your home 85% of the time and only using your other heat source (furnace) a small amount of the time.  The heat pump is considered the work horse or the heart of your system.  Once the temperature outside goes below 35 degrees, then your gas or electric furnace will activate the burners or heat strips to heat your home.  When your system is installed or when you get it serviced, the technician can set the lock-out temperature.  The lock-out temperature of 35 degrees is industry standard for the Puget Sound area.  So when the outside air hits that 35 degree temperature the heat pump communicates with the thermostat and kicks on the backup heat (furnace).  

The heat pump is your first source of heat and your electric or gas furnace is your second source of heat.  Heat pumps that have a Heat Seasonal Performance Factor (HSPF) 7.7 to 9.0 rating (what the heat pump is rated for in the heating season) will save you money on your utility bills and be energy efficient.  So if you have a heat pump as your first source of heat with electric furnace as your backup heat source system, you would typically pay approx. $480 annually².  Versus an electric furnace as your only heat source, you would typically pay $1,266 annually².  So you can see that a heat pump/electric furnace combination could save up to $786 annually².  That’s quite a savings.

The other nice feature for us Washingtonians, is that we get the added bonus of air conditioning during our short hot summer months.

For more information on rebates in Olympia, Thurston County and Tacoma, Pierce County, click here.

1 Wikipedia Definition, http://en.wikipedia.org/wiki/Heat_pump

2 Tacoma Power Home Heating Cost Comparison, http://www.mytpu.org/files/library/heat-pump-cost.pdf