Don't Touch That Dial

Many heat pump owners victims of bad advice

Having the outdoor thermostat set properly is one of the keys to getting the most savings from a dual-fuel heat pump.

Many homeowners who use dual fuel heat pumps are buying more energy than they need-but it's not their fault.

"There's a lot of wrong information floating around on how to operate dual fuel heat pumps," says WEMC's Howard Turner, director of member services and marketing. "It's sad to see someone invest money in a dual fuel system hoping to save money only to have their energy bills go up."

Heat pumps work by moving heat from the atmosphere to the inside of the home during the winter. Since heat pumps move rather than create heat, they operate at much higher efficiencies than systems that burn fossil fuel.

When temperatures fall into the 20s (only a few hours a year in the South), most heat pumps depend on auxiliary heat to make sure the home stays comfortable. While most heat pump systems depend on electric resistance heat for a little help, dual fuel heat pumps use a gas furnace-hence the name dual fuel.

In a dual fuel heat pump, the heat pump's compressor does about 85 percent of the work and the gas furnace heats around 15 percent of the time. Both fuels work when they're most efficient.

But some homeowners are the victims of bad advice on operating their equipment. And with natural and propane gas prices higher in recent years, they're paying much more to heat their home than they should.

"Some homeowners have been told to completely switch off the heat pump during the winter by moving the thermostat to the emergency heat setting," says Turner. "Walton EMC's rates are lowest in the winter, so it makes sense to use electricity for the bulk of their heating needs. But heating totally with the furnace means they're buying lots of gas when it costs the most. It also means they're only using half of the heating system they paid a premium for."

The only time any heat pump, electric or dual fuel, should be set on emergency heat is when the outdoor unit fails. Emergency heat is designed to provide minimal heating until the repairman arrives.

A similar problem happens when the dual fuel heat pump's outdoor thermostat is improperly set.

The outdoor thermostat's job is to determine when the heat pump switches from electricity to gas. If it's set at too high a temperature, the system switches from electricity to gas too early. This means the homeowner misses out on some of the economical electric heating.

"A good heating and air contractor will perform calculations to determine the proper outdoor temperature for the dual heat pump to switch from electricity to gas," says Turner. "This temperature, called the balance point, is usually around the 30s for a properly designed system. Setting the outdoor thermostat higher than the balance point means less-than-optimum use of the dual fuel system and higher energy bills."

Setting any heat pump's thermostat to emergency heat is a no-no except when the outdoor unit fails.