Seven Common Myths About Heat Pumps
By: Chandu Visweswariah
The two biggest sources of carbon emissions in our part of the country in the Northeast are transportation and building heating. Most homes and buildings are heated with a fossil fuel furnace, burning fuel oil, gas or propane to produce heat. To decarbonize rapidly, we urgently need all new construction to incorporate heat pumps, and all existing built infrastructure to be retrofitted with heat pumps.
Heat pumps use electricity to compress a refrigerant such as Puron (industry name ‘R-410A’) and then let it evaporate. The Puron undergoes a phase change, creating a hot side and a cold side. This mechanism allows the heat pump to efficiently cool or heat your home, similar in principle to a refrigerator or air conditioner.
Heat pumps are not furnaces. Nothing is burned in a heat pump. A heat pump doesn’t actually create heat, all it does is move heat against the gradient. For example, in winter, it moves heat from outdoor ambient air or from the earth into your house where it is warmer. In summer, it moves heat from your house to the outside where it is warmer. Heat pumps are ‘reversible,’ meaning that the same machine has a heating and cooling mode. This means that when it comes time to think about a new air conditioning system for summer, the same system could be used to replace your winter heating system.
In my role as an ‘Energy Coach,’ I often visit people’s homes to help them think through decarbonizing and money-saving improvements like heat pumps, solar panels and tightening the envelope. In these encounters, I have found that most people don’t really understand heat pumps. Hence, I decided to write this blog to hopefully clear some of the myths and mysteries around the subject.
Myth #1: Heat pumps don’t work in extremely cold weather.
False. Over the last four decades, heat pumps have steadily improved in terms of cold-weather efficiency. In a recent Department of Energy contest, a manufacturer called Rheem demonstrated an Air Source Heat Pump (ASHP) with very impressive efficiency at an ambient temperature of -22oF (-30oC).
Many people think that they need a source of “backup heat” for the coldest days but this turns out to be untrue.
Even a few years ago, air handlers (which sit inside the house and blow hot or cold air into living space) often had electrical coils in them called ‘supplemental strip heating.’ If the thermostat signaled to the air handler that the system was having trouble achieving the desired temperature, strip heat would come on to supplement the heat pump. Picture a glowing hot electrical coil over which air is blown. Of course, this is only used a few times a year, so the relative inefficiency of strip heat doesn’t matter.
With further advances in air-source heat pumps, any kind of supplemental heat, whether electrical strip heat or a fossil fuel backup, is not required.
Bottom line: you can rest assured that a well-designed heat pump system will keep you comfortable on both the hottest and coldest days without any supplements or backups.
Myth #2: Heat pumps will cost me a lot of money.
False. As we will soon learn, heat pumps are quiet, comfortable, clean, reliable, good for health, good for the environment… what’s the catch? It sounds too good to be true.
Well, it is true that the up-front cost of a heat pump system is higher than a traditional furnace. This is particularly the case if a retrofit involves fabrication and installation of ductwork. But buying
a fossil fuel furnace is like buying an incredibly inefficient car – you will pay for it, and then some, over the lifetime of the equipment. Both heating and cooling costs are reduced due to the efficiency of heat pumps, generally saving residents money every month (depending on local prices of fuel oil, fracked gas or propane vs. the cost of electricity).
In addition, generous subsidies are available due to the Inflation Reduction Act (IRA) at the Federal Level and the New York Environmental Bond Act at the State level. For example, the Federal Government will allow you an uncapped tax credit equal to 30% of your full project cost if you invest in a ground-source heat pump system, and the State will give you a tax credit of 25% up to a maximum of $5,000. For an air source heat pump, you will get a Federal tax credit of 25% up to a maximum of $2,000 per year, and even higher subsidies if your household annual income is below 150% of AMI (Area Median Income). Details of available subsidies can be found in this handy 1-page summary courtesy of Climate Reality Project.
Myth #3: I can simply swap my fossil furnace for a heat pump.
Not necessarily true. A lot depends on how heat is distributed in your home. Heat pumps only work with distribution of heat by forced air. So, if you already have a forced air distribution system, then it may be possible to simply swap a traditional furnace for a heat pump. However, a traditional fossil fuel furnace can produce very hot water (at say 180oF or 82oC) or steam which can then be circulated in baseboards or radiators for heating purposes.
Heat pumps cannot achieve such high temperatures, and so they simply will not work with baseboard or radiator heat distribution systems. Note that some homes that have radiators or baseboards have air ducts for air conditioning in the summer, in which case it is possible to take advantage of those same air ducts for heating purposes as well. With an air duct system, despite the name, a “heat” pump can cover both your heating and cooling needs.
Bottom line: if your existing heat distribution is by radiators or baseboards, then a retrofit will require not only one or more heat pumps, but a forced air heat distribution method (see myth #4 below).
Myth #4: Retrofitting an existing home is almost impossible.
False. Let’s digress for a moment and understand the three most common types of heat pumps: ground-source heat pumps (GSHPs), air-source heat pumps (ASHPs) and ‘ductless mini-splits.’
- A GSHP, sometimes erroneously referred to as a geothermal system, uses the earth as a temperature reference. It requires a loop of tubing in the ground, typically by digging one or more wells on the property. Fluids are circulated in these tubes that feed into one or more heat pump/s which is/are installed in the basement or attic. The heat pump produces hot or cold refrigerant that is circulated in a coil in an air handler that blows hot or cold air into the living space through air ducts. Such a heat distribution system is called a ‘ducted’ or ‘central’ forced air system. The receptacles from which hot or cold air come out are called registers, and the openings though which air returns to the air handler are called vents.
GSHPs are more expensive to install, receive more subsidies from the Federal Government (see myth #2 above), and are more efficient than air source heat pumps especially on the coldest days.
- An ASHP uses the ambient outside air as a temperature reference, so no wells and no underground tubing are required. It produces hot or cold refrigerant that is circulated in a coil in an air handler that circulates air into the living space through ducts, registers and vents.
ASHPs are less expensive to install, receive lower subsidies from the Federal Government, and are slightly less efficient than GSHPs, especially on bitterly cold days.
- A special kind of heat pump comprises an ASHP and air blower without requiring air ducts. These are called ‘mini-split’ or ‘ductless’ heat pumps. You may have seen these above the entry door in small restaurants or shops. The ASHP sits outside the building and the fan portion that blows hot or cold air sits inside the building. The tube that carries the hot or cold refrigerant is called a ‘line set.’ A single ASHP sitting outside the building can feed multiple air blowers in different rooms via multiple line sets (see figure).
Mini-splits are fabulous and relatively inexpensive solutions when duct work is not a possibility. However, they can be a bit noisier than a central system (but less so than a window air conditioning unit), and since heating or cooling blows in from just one place in the room, the heating or cooling is less uniform, leading to ‘hot spots’ or ‘cold spots.’ Newer mini-splits have vertical and horizontal swings to better distribute air. A mini-split approach can be ideal in smaller spaces, and in situations where you may want to take on projects one room at a time. For example, a central gathering area in the home where you spend a lot of time like a family/kitchen/dining room area, or in bedrooms.
For all practical purposes, ASHPs are the preferred solution for almost all situations. The choice of ‘central’ or ‘ductless mini-splits’ depends on the possibility of having air ducts for heat distribution.
What does all this have to do with retrofits? The short answer is that these options give us a plethora of solutions depending on your home. Below are three solutions that are sequentially applied, i.e., go to the second solution only if the first doesn’t work, and so on.
If your home already has air handlers and reasonably-sized ducts, then it is the simplest possible retrofit with an ASHP.
If not, a central ducted system with its quietness and comfort may still be the best solution for you. For example, one air handler could sit in the basement and feed the lower level of your home through registers in the floor, with the ductwork in the basement and/or crawl space. Another air handler could sit in the attic and feed the upper level of your home through registers in the ceiling with the ductwork in the attic. Skilled vendors are very clever with snaking ducts through closets or ‘boxed out’ framing covered with sheetrock even when it is seemingly impossible to get ducts to a section of living space.
If not, one or more mini-splits can be considered, each with one or more line sets, each feeding a different zone of your living space, with absolutely no necessity for ducts. And of course, you could have a hybrid solution whereby some areas of your home are conditioned by mini-splits while the rest of the home has a central ducted system. This works particularly well when there is an area of the house that is particularly cold or hot (sunny spot, large picture windows, entry way) – the mini-split efficiently conditions this space, and the central system turns on much less often as a result.
Bottom line: following this line of reasoning, it is always possible to find an efficient and effective retrofit solution.
Myth #5: My home has no air quality problems.
False. All fossil heating systems produce particulate and gaseous emissions which are harmful to human health. Even with the best venting systems, some of the emissions creep into the building. A little-recognized side benefit of installing heat pumps is vastly improved air quality and concomitant health benefits.
Bottom line: Do you want your family to inhale, on a daily basis, poor quality air with nitrous oxide, carbon monoxide and fine particulate matter?
Myth #6: Heat pumps are exotic and risky.
False. My in-laws built a home in the chilly Poconos in the early 1990s and it was heated exclusively by ASHPs… which is still the case in that house 30 years later. Cold-climate heat pumps are well understood, made by reputable manufacturers (such as Mitsubishi, Daiken, Bosch, and Carrier), and installed and serviced by reliable vendors in almost every neighborhood. Courtesy of Sustainable Westchester, here is a list of local vendors in Westchester County.
My own home has been heated and cooled by heat pumps since 2009 without any backup. Just as furnaces are cleaned and tuned up annually, heat pumps are annually checked, and fluid pressures adjusted as part of a service contract.
Myth #7: For decarbonization, heat pumps must run on clean electricity.
False. Heat pumps are incredibly efficient machines! How efficient? They typically have a Coefficient of Performance (COP) of 3.5 to 4.5 in heating mode, which means that they are 3.5 to 4.5 times more efficient than a conventional furnace. In other words, they use 3.5 to 4.5 times less primary energy to heat your home. (As an aside, investing in a heat pump is the most effective building decarbonization method. If you invest in a tighter envelope by improving insulation, it may reduce energy use by 15% or 20%, but it can’t compete with a heat pump reducing your energy consumption by a whopping 75%!)
For illustration purposes, if your fossil furnace emits 100 units of greenhouse gas emissions, to first order the heat pump will use electricity that causes only about 25 units of carbon emissions to generate. Of course, it depends on how that electricity is generated. If it is from a renewable source such as community solar or a clean Energy Service Company (ESCO) or Community Choice Aggregation (CCA) or your own solar panels, then it is 100% clean and emissions are practically zero. If it runs off the grid in New York, it is 30% clean on average and 70% produced from fossil sources. The bottom line is that even if the electricity is produced ‘dirtily,’ moving to a heat pump reduces your total emissions due to its amazing efficiency. Besides, as the grid is cleaned up in future years, the decarbonization savings automatically increase! In New York, the grid is expected to be 75% clean by 2030, so your heat pump’s effective emissions will automatically reduce every year between now and then.
In cooling mode, heat pumps typically achieve a SEER (Seasonal Energy Efficiency Ratio) of 20 compared to 10 SEER for older air conditioning units – thereby halving the amount of electricity needed.
The bottom line is that decarbonization benefits accrue irrespective of your electricity source. (By the way, the same is true of an EV purchase – by virtue of being 3 to 4 times more efficient than an internal combustion engine, decarbonization benefits accrue almost irrespective of electricity source for charging.)
Bottom line, the benefits of heat pumps stack up:
- “Heat” pumps also provide air conditioning for your cooling needs.
- Lower Total Cost of Ownership (TCO) which includes the up-front capital expense as well as month-to-month operating expenses. The payback period on the additional initial investment is often in the five-to-six-year range, and even better than that depending on subsidies.
- Investing in heat pumps increases the value of your property.
- Health benefits due to cleaner air in your home.
- Greenhouse gas reduction irrespective of electricity source.
- Fossil fuels do not have to be mined, refined, processed and transported to your house – leading to even more emissions savings!
- Your money encourages clean technology R&D instead of going to fossil fuel companies!
[The author gratefully acknowledges review and feedback from Mr. Anil Gowda and Mr. Bert Picardi of Vtronix LLC.]