Straight Talk Articles
Which Heat Pump Option is Right for My Home?
Dear Pat and Brad:
I’ve heard heat pumps are a good alternative for heating my home. It looks like there are a few different types available. Can you explain my options? – Brett
Good idea to check out heat pumps. The technology has improved a lot over the past 10-20 years and is likely to be at least 20% more efficient than what you have right now.(1) The added bonus of heat pumps is they can cool your home in summer, which we’re all looking for after a hot summer.
Modern heat pumps can operate effectively in sub-zero weather,(2) 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 air-source heat pumps.
1. Ducted heat pump
If your house has a forced air furnace, a centralized air source heat pump can work well. A compressor outside your home that looks like an AC unit is hooked up to your home’s existing duct system. Like your furnace, the temperature is controlled through one main thermostat. This is a good solution if your system has decent quality ductwork that heats and cools every room evenly (which is pretty rare).
Ductwork in most homes is not designed to heat or cool every room evenly. Long supply runs provide little air to some rooms. It’s typical for some rooms to lack return air registers. And ductwork is often leaky, which creates comfort problems. If leaky ducts are located in unheated areas such as crawl spaces or attics it will drive up heating and cooling costs. Poor ductwork will render any kind of central heating or cooling system much less effective. Some HVAC contractors can fix some ductwork problems if ductwork is accessible.
Heat pumps vary in efficiency, and this is measured in two ways. The HSPF rating measures heating efficiency and the SEER rating measures cooling efficiency. The minimum ratings for a new heat pump are HSPF 8.2 and SEER 14. Heat pumps with the ENERGY STAR® label are significantly more efficient than the minimum standard. The quality of the installation also matters. Some contractors have more experience and training than others.
2. 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 the answer. 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.
3. Geothermal (ground-source) heat pump
Several feet underground the temperature remains constant all year, somewhere between 45° and 75° F, depending on latitude(3). Heat is transferred into the ground or out of the ground by pipes buried in a loop ten feet underground or drilled up to 400 feet into the earth(4). 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, since the earth’s temperature is warmer than the outside air in the winter and cooler than the outside air in the summer. This efficiency has a price tag, though, which is the initial cost to install the pipe loop or drill the hole for a vertical pipe
I hope this column gives you a good start in your investigation of heat pumps. You might find some more information from your electric co-op. If you have a qualified auditor in your area, an energy audit would be a great next step, especially if it includes a duct leakage test. Then you’ll be ready to talk to contractors and get a few quotes. Good luck!
This column was co-written by Pat Keegan and Brad Thiessen of Collaborative Efficiency. For more information on which type of heat pump is beat for your home, go to the October 2021 more information page.
The condenser for a mini-split is often mounted on an exterior wall. Source: Marcela Gara, EE image database.