Why Aren’t we Installing More Air Source Heat Pumps?
Determining how to heat and cool a home is one of the most critical decisions that homeowners and builders can make when it comes to designing a home.
According to the U.S. Energy Information Administration, on average more than half of a household’s annual energy consumption is used for heating and cooling, making it the largest energy expense for homeowners. Between 2007 and 2012, the average household spent $700 on heating using natural gas and $1,700 using heating oil.
This consumption varies greatly depending on the geographic location, home size and structure, equipment, and the type of fuel used. Households in the Northeast and Midwest regions of the U.S. consume more energy than those in the South and West regions due to their colder climates. Studies show that it takes four times more energy to heat homes in the U.S. than it does to cool them.
Heat pumps are an energy efficient alternative to more traditional heating and cooling options like furnaces and air conditioners. Heat pumps are unique in that they use electricity to bring in heat or cool air from outside to draw it into the home.
There are a few different heat pump systems that builders and homeowners can choose from to heat a home, including:
Ducted Air Source Heat Pumps
Ductless Air Source Heat Pumps, also known as a Mini-Split Heat Pump
Geothermal Heat Pumps
Absorption Heat Pumps
Behind gas furnaces, Air-Source Heat Pumps (ASHPs) are the most common heating systems in the U.S. Most ASHPs are air to air heat pumps which operate by absorbing heat from the outside air and then transfer it directly into the home via a fan system.
How ASHPs operate to heat and cool a home.
ASHPs provide a variety of benefits to homeowners. While they do increase electricity consumption when compared to a gas furnace, most modern ASHPs reduce electric consumption by at least 50% when compared to electric furnaces and baseboard heaters.
While they are the most popular among heat pumps and offer a variety of benefits, they are still underutilized. In 2021, of over 200,000 homes submitted via Ekotrope RATER, only about a quarter of such installed ASHPs.
Heating system data from homes submitted via Ekotrope RATER in 2021.
Going forward, we will need to curb our reliance on fossil fuels in order to achieve our climate goals. It is very possible- and increasingly more likely- that renewable energy alone will power the world by 2050. To prepare for the future, homeowners and builders should stop installing gas furnaces now in order to ensure that homes have the necessary systems in place for when we are no longer using fossil fuels like gas and propane to heat our homes.
Now, knowing that these systems are almost certainly going to entirely replace traditional gas furnaces within the next 30 years you may be wondering, “Why aren’t we installing more air source heat pumps?”
Gas Furnaces are the Status Quo
Nearly 75% of homes built in 2021 were fitted with gas furnaces as their dominant heating system. This is mainly because they have been the traditional heating system of choice for decades. They are what homeowners and installers are used to, aware of, and most comfortable with. Gas furnaces are also typically the cheapest heating system option, both in terms of installation and monthly energy bills.
Most builders and homeowners install gas furnaces along with air conditioning systems to heat and cool the home. A/Cs are essentially heat pumps that cannot be used in heating mode. Rather than installing an A/C along with a gas furnace, for a similar cost you can install an ASHP with a gas furnace. That way, you get the benefits of cheaper utility bills using the gas furnace as your primary heating system right now while still being prepared to make the switch to electric in the future.
When compared to gas furnaces, installing ASHPs have major advantages, including that they:
Can run on clean, renewable energy and use just 1 unit of electricity for 3-4 units of energy produced.
Can be used for both heating and cooling- using less space and, in some cases, the cost of installation can be cheaper than installing a furnace with an A/C.
Require no in-house combustion or fuel storage, making them safer.
They don’t require ducts. Ductless mini-split systems can be installed in existing buildings without ducts and are very efficient.
Incentive Systems Give Equivalent Credit for Gas and Electric
Most of the incentive systems that have been set up to encourage energy efficiency give out similar credit for homes that use gas as those that use electricity:
It is just as easy and often easier for homes to meet energy codes with gas equipment.
Rating systems like HERS, ENERGY STAR and DOE Zero Energy Ready are designed such that gas homes get similar scores as electric homes.
Most rebates, tax credits and other incentive programs award similar amounts to homes that use gas as those using electricity.
There are some hints of this changing:
RESNET is launching a CO2 index that will give a lower score for similar homes using electric systems
Mass Save recently launched an All-Electric Home Incentive program that provides a much larger incentive for all-electric homes than is available for gas.
Accelerating these changes will increase the adoption of ASHPs.
Cost
While ASHPs use just one unit of electricity for every 3-4 units of energy produced, ASHPs are usually slightly more expensive to heat a home than gas furnaces. This however, varies based on electricity and gas prices, climate zone, and the efficiencies of the individual systems being compared. On average, when using ASHPs in homes in colder climate zones you will see higher heating bills than those in warmer climates.
However, when compared to oil furnaces, ASHPs are far more cost-efficient to heat and cool a home. The cost to operate a heat pump per mmbtu is 45% less than heating oil, 52% less than kerosene and 49% less than propane- thus making an ASHP a no-brainer when compared to an oil furnace.
Cost of heating fuels comparison chart.
ASHPs are also expensive to purchase and install. On average, central heat pump systems cost between $3,000 and $5,200. In addition, the installation typically costs somewhere between $10,000 and $20,000. This cost is amplified when retro-fitting a home that does not already have an existing duct system, as installing a complete duct network costs anywhere from $12,000 to over $18,000.
However, one major advantage of installing ASHPs is that there are Federal and State rebates for installing ASHPs, up to $10,000 in states like MA.
The Effects of Climate Zone on Energy Use and Efficiency
Energy consumption for heating and cooling a home varies greatly. This difference is most obviously exemplified by geographic locations, as areas such as the Northeast and Midwest can experience drastic changes in temperature throughout the year. While ASHPs can work at temperatures as low as -4°F, their level of efficiency begins to wane at 32°F. This is because they depend exclusively on outside air and as the temperature drops, so does the heat output that the pump can produce.
In recent years ASHP technology has advanced to the point where it can provide legitimate space heating alternatives for colder climates. Cold climate ASHPs are a viable alternative for those living in colder areas. However, these systems are more expensive: $8,000-$9,000 more compared to a gas furnace and $5,000-$6,000 more than other ASHPs.
While annual energy use costs for ASHPs are higher in colder climates, by about $275 in Denver and nearly $700 in Minneapolis according to this study by Home Innovation Research Labs, it is important to note that the specific heat pump system choice affects the cost and the heating performance of the system during colder months.
For those living in colder climate zones and looking to spend less on installing a heat pump system, there are still viable heat pump solutions that will work for your home. Ductless heat pumps, or mini-split heat pumps, are capable of providing comfortable heating for a home when outdoor temperatures are as low as -15 °F. They’re also a great option for homeowners retrofitting a home’s HVAC system as they do not require an existing duct system to be in place. Read more about how ductless heat pumps work.
Noise
ASHPs can be noisy compared to other heating systems. ASHP’s compressors and fans can generate more noise depending on the air velocity, pressure flow, fan speed, and the gap between the temperature of the air outside the refrigerator and the temperature where the refrigeration cycle occurs. That being said, the amount of noise produced by heat pumps is generally quite low.
Noise scale comparing heat pumps to other relative items.
ASHPs are an exciting alternative to traditional fossil fuel heating systems. They represent the future of electrification and are critical to a sustainable future that is free of fossil fuels. It is important that homeowners and builders understand that these systems are going to become the norm and that choosing to install these systems now rather than waiting until later will prepare you for the future.
While there are a few key factors for why we aren’t installing more ASHPs, we believe it is important that builders and homeowners start making the switch. Do you agree? Tell us your thoughts on the matter in the comments below!
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