Dr. David Kuchta has 10 years of gardening experience and has read extensively about environmental history and energy transitions. He has been an environmental activist since the 1970s, as well as a historian, writer, gardener, and educator.
Heat pumps function like refrigerators or air conditioners because they take warm air from one room and send it to another. In winter, a heat pump transfers heat from outside to indoors, and vice versa in summer.
As global average temperatures continue to rise, demand for air conditioning is expected to quadruple by 2050, exacerbating the climate crisis. Conversely, the use of a heat pump can significantly reduce a building’s greenhouse gas (GHG) emissions. In this article, we discuss how heat pumps can be a more sustainable option, along with the benefits, costs, and buying tips for other buyers.
There are two main types of heat pumps, both of which can be used as heaters or as coolers and water heaters.
Ground source (or “geothermal”) heat pumps deliver a mixture of water, antifreeze and/or refrigerant through a network of pipes that run below the frost line. As the liquid passes through the pipe, it acts as a heat exchanger, absorbing the heat from the ground. The liquid is then sucked into the compressor, where it is further heated to produce steam. The heat pump’s fans then distribute the warm air through pipes or ducts throughout the building.
In the summer, ground source heat pumps reverse this process by drawing warm air out of the home and storing it in the soil.
A heat exchanger is any device that transfers heat from one liquid to another without mixing the liquids.
Air source heat pumps extract heat from the air, not from the ground. The outdoor unit fan draws air from the atmosphere and forces it through the heat exchanger coil containing a very low boiling point liquid refrigerant.
As it boils, the refrigerant is fed through the compressor, where it is additionally heated. The compressed steam then passes through similar coils in the indoor unit, heating it up. The fan then releases the heat from the refrigerant into the air and distributes it throughout the home.
As it cools, the refrigerant passes through the expander (as opposed to the compressor) and returns to a liquid state. The refrigerant is then sent to the outdoor coil to restart the process.
As with ground source heat pumps, reversing valves inside the heat pump allow the same process to be used as an air conditioner in summer.
Ground source heat pumps are not affected by changes in atmospheric temperature because the ground below the frost line remains relatively stable. Not so long ago, air source heat pumps were not efficient enough to operate in extremely cold climates. But today there are heat pumps in Antarctica, northern Canada and northern Europe. The refrigerant temperature in an air source heat pump can range from -15 to -56 degrees Fahrenheit. Any air above the temperature of the refrigerant will turn it into vapour.
Air source heat pumps have to work harder (and therefore use more electricity) to extract heat from very cold air. However, at sub-zero temperatures, high-performance heat pumps are twice as efficient as natural gas heating systems.
More than half of the energy in residential and commercial buildings is used for space heating/cooling and water heating. That’s why commercial and residential buildings account for 34 percent of global greenhouse gas (GHG) emissions, including 13 percent of total US greenhouse gas emissions.
How a heat pump can reduce these emissions depends on many factors, including the source of electricity used to run the heat pump. In 2021, 40% of US electricity will come from non-fossil fuel sources, so in most of the US, electric heat pumps will be cleaner than burning fossil fuels in the basement. Safer too: Between 2010 and 2015, 2,244 Americans died from accidental carbon monoxide (CO) poisoning caused by incomplete combustion of fossil fuels. Most deaths from CO occur during the winter.
By using your own rooftop solar panels to operate your heat pump, you virtually eliminate greenhouse gases and potential carbon monoxide emissions from heating and cooling your home.
Buying a heat pump is more cost effective than buying a gas oven and air conditioning system.
According to Forbes, the average initial cost of an air source heat pump in July 2022 is between $3,500 and $4,500, with $2,500 to $10,000 depending on the complexity of the installation. Similarly, the average cost of a gas oven is $4,500, the base oven (pre-installation) costs $1,690, and the high-efficiency model costs $6,910 to install.
Given the earthwork and plumbing required, the initial cost of a ground source heat pump can be significantly higher, ranging from $14,000 to $42,000 for most systems.
Remember that a heat pump replaces not only the heating system, but also the cooling system – you get a 2-in-1 offer that saves thousands of dollars. (The national average price of a new central air conditioning system is about $5,600 plus installation costs.)
According to the US Department of Energy, air source heat pumps are capable of “providing three times as much heat to a home as it consumes,” depending on the region. This can be more than three times the efficiency of new natural gas stoves, the most efficient of all fossil fuel stoves. (The old stoves were half as efficient as the new ones.) Geothermal heat pumps are more efficient, using 44% less energy than air source heat pumps.
Due to the increased efficiency, the annual operating costs of a heat pump are almost always lower than those of a gas stove – depending on the home’s heating needs, electricity prices and natural gas prices.
In all but three states (Alaska, Michigan, and New Mexico), heating a home with an air source heat pump costs less than a high-efficiency gas stove. In the state with the largest cost disparity (Maine), heat pumps saved more than $13,000 over 15 years compared to gas ovens. This is the price of your next heating system.
While heat pumps and central air conditioners are comparable in efficiency and running costs, window air conditioners tend to have higher running costs.
Air conditioning and HVAC systems are the most energy intensive appliances in your home, accounting for 12% of the average US electricity bill. (In the south, that figure could rise to 27 percent.) These costs will only increase as climate change pushes average temperatures further higher. Electrically powered heat pumps can help minimize this cost increase.
The cost of fossil fuels, a major driver of inflation, has historically been more volatile than the cost of electricity, which is often regulated by public utilities. (Of course, in a market that uses fossil fuels to generate electricity, the two costs are linked.) As noted above, 40% of the US power grid already runs on non-fossil energy. As more cheap and price-stable renewable energy enters the U.S. grid, the economic benefits of electric heat pumps will become more apparent, allowing U.S. consumers and businesses to rely on stable heating at a time when energy demand is on the rise. homes can be reduced, and cooling costs can be reduced. . is growing.
Federal and state incentives can further reduce the cost of heat pumps. The Inflation Reduction Act of 2022 provides a tax credit for the purchase and installation of heat pumps of up to $2,000. You can also find state and local government incentives available in your area. Your local power company may also offer incentives to switch.
Yes. Ductless heat pumps are used to modernize houses without ducts. Indoor air handling units are connected to an outdoor unit and then distribute the air around the house.
The ODP value depends on the type of refrigerant. Refrigerants containing CFCs were phased out after the signing of the Montreal Protocol in 1987, and HCFCs were listed in 1992. Hydrocarbons such as propane and isobutane have a much lower global warming potential and are therefore greener refrigerant options.
IPCC, Climate Change 2022: Climate Change Mitigation. Summary for Policymakers, WP-7, US Environmental Protection Agency, Sources of Greenhouse Gas Emissions.
“Renewable energy sources are inherently sustainable compared to fossil fuels.” Melody, Lauren and Christina Carlson. “Energy Price Stability: Fossil Fuel Hazards and Renewable Energy Perspectives,” Roosevelt Institute, May 11, 2022.