Two of the most popular types of heat pumps are air source heat pumps and ground source heat pumps. While both can significantly reduce energy bills, they work in slightly different ways.
Understanding the differences between air source and ground source heat pumps will help you pick the one that’s the most efficient, cost-effective, and practical option for you.
If you’re thinking about investing in a heat pump but aren’t sure which type to buy, keep reading - or check out our guide to selecting the best heat pump for your home for a broader overview. In this article, we’ll tell you everything you need to know about the different types of heat pumps and what you need to consider before buying one.
Despite the name, a heat pump can both warm and cool your home. Heat pumps use standard electric motors and compressors, like those found in air conditioners and refrigerators. Instead of generating heat like a furnace or cooling the air like a traditional air conditioning system, heat pumps transfer heat from one area to another.
In winter, a heat pump pulls heat from the air or ground outside and moves it into your home to keep it warm. In summer, a heat pump keeps your home cool by moving heat from inside your house to the outdoors.
Because heat pumps don’t burn fuel to generate heat or cool air, they’re much more efficient at heating and cooling than furnaces or HVAC systems. Installing a heat pump can help you cut your energy costs and lower the carbon footprint of your home.
Air source and ground source heat pumps both move heat into and out of your home. The big difference between the two is how they do it.
Air source heat pumps transfer heat from the air, while ground source heat pumps transfer heat from the ground.
Air source heat pumps use a heat exchanger and a compressor to move heat from one area to another. In the winter, the heat pump's outdoor unit pulls heat from the air. The heat is absorbed by the refrigerant and turned into gas. The system compresses the gas to make it even hotter. The heated air is then released into your home. In the summer, the process switches direction - moving heat from inside your home, outside.
Ground source heat pumps (also called geothermal heat pumps) work the same way, but with one big difference: instead of pulling heat from the air, they absorb it from the ground through buried pipes filled with water and refrigerant. This works because ground temperatures stay relatively warm, even in cold weather.
So, which heat pump is the best option? Let’s see how they stack up against each other.
When comparing air source heat pumps and ground source heat pumps, you need to look at more than just the price. Making the smartest decisions means weighing up the differences between the two and thinking about the total cost and performance over the system’s lifetime.
When it comes to the upfront costs, air source heat pumps are a cheaper option. Installing an air source heat pump is simpler than putting in a ground source heat pump, so labor costs are lower.
Air source heat pumps typically have installation prices ranging from $3,500 to $8,000 for ductless systems and anywhere from $10,000 to $20,000 for ducted systems, depending on the size of the unit and the amount of ductwork required.
To install a ground source heat pump, technicians will have to excavate or drill into the ground to create trenches or bore holes for the pipes. The cost of this varies depending on the type of system and the ground conditions, but it’s typically within the range of $20,000 to over $50,000.
Ground-source heat pumps are more disruptive and take longer to install than air-source heat pumps because they require underground piping. Depending on the property, installers must either dig horizontal trenches or drill deep vertical boreholes so the system can transfer heat to and from the ground. It can take several days to a few weeks to install a ground source heat pump and involves a fair bit of landscaping work.
And you do need some space. Horizontal systems require about 10,000 to 30,000 square feet of open yard space and trenches that are up to six feet deep. A vertical system only needs 11 to 25 square feet per borehole. Typical-sized homes usually require three to four boreholes at about 15 feet apart.
Installing an air source heat pump is simpler and faster than installing a ground source heat pump. It’s a lot like installing an air conditioning system. The process involves setting up a unit outside the home and installing an indoor unit. Even if you need to have ducts installed or upgraded, installing an air source heat pump system usually only takes between one and three days. The outside unit will take up about 20 square feet of space next to the house.
So far, it might seem like air source heat pumps are the better option. But when it comes to efficiency, ground source heat pumps take the lead.
Heat pump efficiency is measured by COP (Coefficient of Performance). This compares how much heating or cooling a heat pump produces to how much electricity it uses.
Because ground temperatures are stable year-round, the performance of ground source heat pumps doesn’t change with the seasons. They score a COP rating of between 3.5 and 5.0.
Air source heat pumps have a COP rating between 2.0 and 4.0. Because they draw air from the outside, air source heat pumps have to work harder in cold weather, which reduces their overall efficiency.
Studies have shown that ground source heat pumps can maintain up to 87% of their efficiency and heating capacity in low temperatures, while air source heat pumps manage up to 55% efficiency.
Bottom line: it’ll cost you a little more in terms of electricity to run an air source heat pump compared to a ground source heat pump.
Air source heat pumps typically last between 12 and 18 years. Ground source systems have an average lifespan of between 20 and 25 years for the indoor components, while the buried pipes can last over 50 years.
The difference here is that outdoor air source heat pump units are continuously exposed to the elements, so their components wear out faster than ground source units.
Main takeaway: While they cost more upfront, ground-source systems are built for the long haul.
Because air source heat pumps have a large outside unit, they require more maintenance than ground source heat pumps. They need an annual service and regular checks to make sure everything is in working order.
Ground source heat pumps also need an annual service, but it's usually easier and quicker than it is for air source units. The underground pipes generally don’t need attention, so it’s just the indoor unit that needs to be checked.
Installing a heat pump can make a huge difference in your monthly heating and cooling costs. Heat pumps are more efficient than electric or gas furnaces and cheaper to run than most HVAC systems. An air source heat pump is 50% cheaper to run than an electric furnace, and a ground source heat pump can help you reduce your heating and cooling costs even further.
Choosing between an air source or ground source heat pump comes down to your home, your budget, and your long-term goals.
An air source heat pump is a good choice if you don’t want to pay higher upfront costs and don’t want to deal with a long installation process. Air source units are also good options if you already have, or can easily add, ductwork and have enough space for an outdoor unit. They're often recommended for milder climates like the Southeast or Pacific Coast, though cold-climate air source models are built to perform well even in freezing temperatures.The ease of installation and low upfront costs mean that air source heat pumps are the most popular choice for US homeowners.
But if you’ve got the land, the time, and the funds, then a ground source heat pump will deliver maximum efficiency and better savings over the long-term. A ground source heat pump will last longer, doesn’t need much maintenance, and will perform consistently in all weather conditions, and use less energy. If you’re in a colder region like the Upper Midwest or Northeast, you can cut your annual energy costs by up to 60% by installing a ground source heat pump.
For more information and advice on heat pumps, contact the team at Switch Together. We can help you decide which type of heat pump will work best for your home.