Cold climate heat pumps: a livable home in cold places
娜奥米·科尔(Naomi Cole)和乔·沃丘纳斯(Joe Vachunas)
With winter weather in full swing across the United States, many of us are wondering if we can really heat our homes in cold temperatures without burning fossil fuels. In the fall of 2021, we had the same issue. Our family's duplex apartment in Cleveland, Ohio, has a 35-year-old gas stove generating electricity. We're big advocates of moving away from fossil fuels, but there's no denying that we're nervous about dismantling furnaces and using only heat pumps for heating. Sure, we do that in our house in Portland, Oregon, but the average winter temperature in Cleveland is 15 degrees Fahrenheit cooler than Portland's, and the snowfall is nearly 50 inches higher. Will this home allow our Airbnb guests to survive the cold Midwestern winters without burning fossil fuels?
At the time, we didn't know that heat pumps in cold climates had kept homes in the coldest regions of the world warm for decades. Norway, Sweden and Finland have the highest heating demand in the world but are leading the way in heat pump installations, which have grown exponentially over the past two decades. Nearly half of Nordic households have a heat pump, while only 13% of U.S. households have a heat pump. In Japan, the birthplace of heat pumps, 90% of households use heat pumps, including cold cities like Saporo with hundreds of inches of snow each year.
The penetration of heat pumps is higher in colder countries. Sources: Japan Center for Heat Pumps and Heat Storage, Nature and the U.S. Energy Information Administration.
In the U.S., while heat pump sales surpassed gas furnaces for the first time in 2022, most heat pump penetration is in the country's southeastern region, where winters are mild. However, from 2018 to 2022, Maine's heat pump sales increased by 300% (9,000 to 28,000 per year) and now has more than 100,000 heat pumps installed in its 600,000 homes.
图片由Efficiency Maine提供
Choose the right heat pump model for your climate
As winter approached, we explored heat pumps and alternative gas stoves (for comparison) and had bids from four companies. Since we don't live in Cleveland, we don't have an existing network of contractors. To find a reputable heat pump installer, we use the manufacturer's website, which allows you to search for certified contractors in your area. (You can do this, for example, on the Mitsubishi, Lennox, and Daikin websites).
We also look at how cold-climate heat pumps work their magic. All cold-climate heat pumps have variable speed compressors (see our heat pump post for explanation) that are more efficient because they can rise and fall as the temperature changes. Cold climate heat pumps also have a number of other features: 1) an electronic expansion valve that can change the refrigerant pressure faster; 2) Intelligent defrost cycle, which can melt any outdoor coil frosting; 3) De-icing of the drain tray to prevent any condensate from freezing; 4) Cold climates run unique computers and algorithms.
We've found some great resources to help with our decision-making process:
1) Carbon Switch reviewed cold climate heat pumps and noted the amount of heat they produce in cold climates. (Mitsubishi is at the top of the rankings.)
2) ENERGY STAR's Cold Climate Heat Pump Classification explains which heat pumps are certified for cold locations. On their website, under the No Pipe or Piped option, you can check the "Cold climate" box (blue box below) to filter heat pumps with that rating.
ENERGY STAR's website shows numbers such as HSPF2 (red box below) that measure the efficiency of a heat pump heating space (8.5 is good, more than 10 is excellent; Some top-of-the-line models have scores over 15). The website also shows how much heat a heat pump produces at 5 degrees Fahrenheit (orange box), and you can compare it to the amount of heat they produce at 47 degrees (green box).
3) Electrify Now's checklist of things to ask a heat pump contractor can help ensure that you get the right size heat pump for your residence. (Full disclosure: Joe is an active Electrify Now volunteer.)
Bidding is underway
We received bids and proposals from four contractors and were delighted, and somewhat surprised, that the cold climate heat pump (Daikin Fit) also offers air conditioning and is the cheapest option at ~$12,000. The price of an efficient gas stove plus air conditioner is much higher at $16,000.
Outdoor cold climate heat pump in duplex. Image courtesy of Mitsubishi.
Cold climate heat pumps typically cost 20-30% more than standard heat pumps because they have additional features that make them work well at low temperatures. There are many cold-climate heat pumps that can work in colder temperatures, but we chose the one with the lowest upfront cost.
The fact that Daikin Fit ranks #3 in the Carbon Switch review above gives us confidence in our choice.
Cold climate heat pump installation
In late October 2021, our selected contractor removed the old gas stove and air conditioner, sealed the gas lines, and installed a new whole-house heat pump. Due to the layout and the existing piping, we chose a piping system. The new heat pump system looks a lot like the old gas + air conditioner, with an indoor unit (air handler) in the basement and an outdoor unit that looks similar to the old air conditioner.
The indoor unit of our new whole-house cold climate heat pump (right) replaces the gas furnace (left)
We did install resistor backup (sometimes called "with heat") to replenish the heat pump on the coldest days. Using resistors is inefficient and more costly, but our installers assure us that the heat pump works at full capacity at temperatures as low as 5 degrees Fahrenheit and has an intelligent algorithm that adds a small amount of resistance heating when the temperature drops below that temperature.
Our installation followed several best practices for cold climate heat pumps, including: 1) lifting the outdoor unit off the ground so that it would not be in snow or ice (if it had to be on the ground, a snow flap would help); 2) Perform heating/cooling load calculations to avoid oversizing the heat pump. It's easy to think that bigger is better, but sizing a heat pump into your home is essential because oversized units will close and open frequently, which can lead to inefficiencies and shorter lifespans than a properly sized heat pump in continuous operation.
Our Cleveland heat pump is mounted on a bracket that lifts it about a foot off the ground
Utilities and comfort
After installation, we waited for the bills and Airbnb reviews to roll in. Will heat pumps use a lot of resistance and increase utility costs? Will our guests notice a difference? Cleveland duplex apartments have created a perfect case study where a heat pump is used on one side and natural gas is still burning on the other. We are happy to report that our utility bills are almost identical after adding the heat pump. It's worth noting that after the first year, the total energy cost for each side of the duplex is within $10. In the two years since installation, we haven't received a single "I'm cold!" from a guest.
We hope our experience will convince you that even if you live in a place where temperatures often drop below freezing, there is a heat pump for you. Heat pump systems work well in the Midwestern states, and the purchase or operating costs are no higher than those of gas furnaces. We're proud to join the millions of homeowners — from Maine to Norway, to Japan, and now Cleveland — who are ditching fossil fuels in favor of clean heating machines that keep homes warm in the coldest climates.