Question

We pay 4X more in winter than in summer to run the heat pumps in our all electric house. How can we set them to minimize heating costs?

Asked by Eric
Fayetteville, AR

There is a feature we have heard about that allows us to set the temperature we want and then the heating system starts early enough to reach that temperature by the time we need it without using the heat strips. These heat strips apparently account for the huge difference between our summer AC and dead-of-winter heating costs. We are told that the heat pump's ability to extract cooling from the outside air "maxes out" at about 104 degrees, and in winter, the system must use the auxiliary strips at about 30 degrees and below. We like the versatility of the heat pump (if not the complexity) but do we have any options? Our units are about 16 years old and may need replacing soon although they are top of the 1994 line and running great.

Answer

Michael Holcomb

Answered by Michael Holcomb

Byron Center, MI

Alliance for Environmental Sustainability (Headquarters)

September 7, 2011

You have my sympathies. All electric homes can be extremely expensive to operate if the home wasn’t designed with a thermal envelope that significantly reduces heat loss/gain.

  • Operating costs rise because you are either using more energy or the energy unit cost has risen.
  • You use more based on age and condition of the equipment, climate conditions and occupant lifestyle changes (i.e. preventative maintenance, thermostat set-points, etc.)

Keeping costs down

There are things you can do to keep the costs as low as possible subject to design limitations.

  • Keep window treatments open during the day to allow in sunlight (converts to heat into the home) and closed at night to keep the heat indoors.
  • Electric resistant heat strips become more costly to operate as they age. Seventeen years is pushing the envelope on design service life. So replacement now would go a long way to reducing operating costs.
  • The other thing to consider is operating the emergency electric heating elements as little as possible.

Setback thermostats are not recommended when using a heat pump

When using a heat pump it is best to find a comfortable heat setting (in cold weather months) and leave it there. Setback thermostats are not recommended.

Most electric backup heating strips are automatically brought on line if there is a 2-degree temperature difference between the thermostat setting and the ambient temperature.

So, if you set the thermostat back during the day (while at work) you can guarantee that you’ll be reheating the house using electric resistance, a very expensive option.

Buying a new heat pump

If you are in the market for a new heat pump you are in luck. Technologies have changed significantly and it is now possible to have an air-source heat pump that operates at much lower outdoor temperatures than your existing system. 

Optionally you might consider installing a ground-source, closed-loop heat pump. In most instances these systems can be sized to provide all of the heat you require, using the auxiliary heat only in the event of a pump failure. As with air source heat pumps you should not use a setback thermostat with ground source heat pumps.

Find ways to reduce your heating/cooling load

Before making a purchasing decision have your home analyzed by an energy auditor to see if there are things you can do to reduce your heating/cooling load.

The money you spend to hire a third-party auditor will be money well spent.

  • They can help you size the equipment and provide a return on investment analysis on proposed improvements before you proceed with upgrades.
  • Make sure that your auditor can provide you with a computer analysis as part of their audit as well as Manual J calculations.

Good luck.

Tagged In: heating cooling

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