Q: I’ve heard heat pumps can be a good alternative for heating my home, but it looks like there are several types available. What are some of the most common options?
A: I think it’s a good idea to consider a heat pump for your home. The technology has improved a lot the past 10 to 20 years. It is likely to be at least 20% more efficient than what you have now. Heat pumps can also cool your home during summer months, which is an added value.
Newer models of heat pumps can operate effectively in sub-zero weather, but sometimes they do so by switching to electric resistance mode, which is much less efficient. In a colder climate, it may be worth investing in a dual fuel system where propane or another fuel provides supplemental heat on extremely cold days.
Here are a few situations where you might use the different types of heat pumps.
Ducted heat pump. If your home has a forced-air furnace, a centralized air-source heat pump can work well. A compressor outside your home that looks like an air-conditioning unit is connected to your home’s existing duct system. Like your furnace, the temperature is controlled through one thermostat. This is a solid solution if your system has quality ductwork that heats and cools every room evenly, which is rare.
Ductwork in most homes is not designed to heat or cool every room evenly. Long supply runs provide little air to some rooms, and it’s typical for some rooms to lack return air registers. Also, ductwork is often leaky, which creates comfort issues.
If leaky ducts are located in unheated areas, such as crawl spaces or attics, it will increase your heating and cooling costs. Poor ductwork will render any kind of central heating or cooling system much less effective. Some HVAC contractors can repair problems if the ductwork is accessible.
Heat pumps vary in efficiency. This is measured in two ways. The Heating Seasonal Performance Factor measures heating efficiency. The Seasonal Energy Efficiency Ratio measures cooling efficiency. The minimum ratings for a new heat pump are HSPF 8.2 and SEER 14. Heat pumps with an Energy Star rating are significantly more efficient than the minimum standard. The quality of the installation also matters. Some contractors will have more experience and training than others.
Mini-split heat pump. If your home does not have ductwork or the ductwork is poorly designed or leaky, a ductless mini-split heat pump might be your best bet. With a mini-split heat pump, tubes connected to the outside compressor carry refrigerant to one or more air handlers, which are mounted high on a wall to distribute air. Thermostats regulate each air handler, providing control of different zones in the home.
In climates that don’t experience extreme cold, a ductless heat pump could supply all the heating and cooling in a small home. They are often used in combination with a central heating and cooling system. Ductless mini-splits are an excellent option if you don’t have central air ducts, your ducts are leaking, or you only want the new ductless heat pump to heat or cool part of the home.
Geothermal (or ground-source) heat pump. Several feet underground, the temperature remains constant year-round—typically between 45 F and 75 F, depending on latitude. Heat is transferred into or out of the ground by pipes buried in a loop 10 feet underground or drilled up to 400 feet into the earth. The pipes carry water to a compressor, which uses a refrigerant to transfer the heat to or from your home’s ducts.
A geothermal heat pump system is extremely energy efficient because the earth’s temperature is warmer than the outside air in the winter and cooler than the outside air in the summer. But this efficiency comes with a high price tag, which is the initial cost to install the pipe loop or drill the hole for a vertical pipe.
Check with your local electric utility for additional information and guidance. If you have a qualified energy auditor in your
area, an audit could be a great next step, especially if it includes
a duct leakage test.