Kathy Heseltine’s mobile home is now equipped with a heat pump system through an Efficiency Maine pilot program that replaced the furnace. Ben McCanna/Staff Photographer

Heat pumps are useful for keeping warm in Maine. But they can’t replace a home’s central heating system on the coldest winter days, especially in an old house.

That was what Kathy Heseltine understood to be true, so she was skeptical when a consultant working for Efficiency Maine came last year to her Freeport mobile home park with an offer. The agency would take out her kerosene-fired furnace and install a whole-house heat pump, free of charge. If she wasn’t happy after a year, the consultant said, he’d hook up the old furnace again.

Today, Heseltine is a heat pump evangelist. The 37-year-old mobile home she lives in with her husband, Sam, is more comfortable in the winter, cooler in the summer, and less expensive to heat. She even convinced a sister to get one.

“This has been a real revelation,” Heseltine said. “We really believe in this product, and I was a hard sell in the beginning.”

The Heseltines are part of a demonstration project that swapped central heating systems last year with heat pumps in 10 mobile homes. The aim was to show that today’s high-efficiency heat pumps can do the job alone in subzero temperatures – and counter a perception that they aren’t suitable as stand-alone heating systems.

The project is the first in the country to study the impact of retrofitting mobile homes entirely with heat pumps, according to Efficiency Maine.


In a separate study, consultants also replaced existing systems in nine stick-built homes, ranging from a century-old condo on Great Diamond Island to a newer single-family home in Sanford.

Taken together, the results are meant to help validate the performance of high-efficiency heat pumps. They’re an essential element of Maine’s Climate Action Plan, which seeks to get 100,000 new heat pumps in homes and businesses between 2020 and 2025, with an additional 115,000 whole-house systems by 2030.

More than 27,000 new heat pumps were installed last year, encouraged by Efficiency Maine rebates that range from up to $1,200 for residents overall to $2,400 for those with low incomes. In a state where six out of 10 homes still heat primarily with oil, the overall goal is to phase out heat systems that use climate-warming fossil fuels, in favor of those that run on renewably generated electricity.

Kathy Heseltine stands near a heat pump, right, that was installed in her home through an Efficiency Maine pilot program. Ben McCanna/Staff Photographer

Mobile homes are an apt testing ground. Maine has more than 62,000 units of manufactured housing, according to U.S. Census data. That represents more than 8 percent of Maine’s housing stock. The dwellings are critical to providing affordable housing in rural communities, and it’s no surprise that heating costs are often top of mind for the people who live in them. That’s true of Heseltine, who is retired.

Heseltine said she can’t tally the savings in energy costs until year’s end, because she pays the same amount for electricity each month on a payment plan. But Efficiency Maine has calculated that mobile home residents should save an average of $1,300 a year, compared to using oil or propane at current prices.

Those savings are based on the frugal way that heat pumps use electricity to transfer warmth present in outside air to indoor space, even during winter, using technology similar to that of a refrigerator.


Based on costs per unit of heat, the Maine Governor’s Energy Office calculates that air-source heat pumps using electricity at 21 cents per kilowatt-hour are less expensive than oil at $4.44 a gallon, kerosene at $5.09 a gallon or propane at $3.29 a gallon.

“There are lots of homes in our state that would be terrific candidates for this solution,” said Michael Stoddard, the executive director of Efficiency Maine. “And people could save a lot of money.”

Central heating systems in mobile homes often consist of small, forced-air furnaces that fit in cabinets or closets. Sometimes called Miller furnaces after a prominent brand, they burn oil or propane and distribute heat through ductwork.

Swapping out the furnaces wasn’t a straight-forward exercise in the pilot project, Stoddard said, because there weren’t any distributors in Maine with a heat pump unit that fit easily into the furnace closets. That increased the total cost of both studies to roughly $14,000 per unit, or $266,000, paid from Efficiency Maine funds. Stoddard said he expects the cost to drop, as more manufacturers offer units designed for mobile home retrofits.


The pilot project got underway last year when David Korn, vice president at Massachusetts energy-management consulting firm Ridgeline Energy Analytics, made a presentation at the mobile home park.


Wardtown Mobile Home Cooperative is a resident-owned community on the rural outskirts of Freeport. The community’s 60 lots feature a mix of older and newer manufactured homes, and the majority have furnaces that burn kerosene or propane. An estimated half of the owners are on fixed incomes.

Marianna Casagranda was at that meeting. As she remembers it, a few people who attended promptly walked out after Korn told them their existing furnaces would be removed for the project. But Casagranda, the Heseltines and eight other owners were intrigued by the offer.

Casagranda lives in a 910-square foot single-wide mobile home. It’s only two years old, had a propane furnace and is better-insulated than most older units. But Casagranda said she saw the opportunity to switch to a cleaner heating system that was less expensive to run.

“I thought, ‘Let’s just see what it feels like for a whole year,’ ” she said. “And I have to say, I’m very impressed.”

There were several nights last winter when the outside temperature hovered near zero, Casagranda said, but her home stayed at a comfortable 68 degrees. And she enjoyed the heat pump’s air conditioning function during last summer’s heat wave.

She’s also happy with her energy bills. In January 2021, her propane bill was $189 and electricity cost $33, for a total of $222.  Last winter, her electric bill that included the heat pump was $142.


“I have been a happy customer,” she said. “I have no interest in going back to propane.”

The Heseltines’ 1,000-square-foot home isn’t as well-insulated and also has a stick-built addition. Kathy Heseltine said the couple was skeptical coming into Korn’s presentation, because they had heard “so much negative publicity” about heat pump performance.

Last winter changed her mind. The house was “toasty warm,” she said. And being comfortable in the summer has been a bonus.

“We never had air conditioning and last summer was a doozy,” she said. “In 15-20 minutes, you’re as chilly as you can be.”

These assessments line up with data being compiled by Ridgeline, the consultant. The coldest temperature recorded during the trial, at Portland International Jetport, was 4 degrees below zero in January.

“We believe that some of the local temperatures at (Wardtown) were actually a few degrees colder,” Korn said.


“All of the homes were able to heat to about 70 degrees or to their preferred temperature, even during the coldest temperatures, according to our metering equipment and according to the 10 customers who received heat pumps.”


Expanding heat pump installation in Maine is part of the Climate Action Plan’s overall vision of beneficial electrification, the idea of replacing fossil fuels for heating and transportation with affordable electricity generated from solar, wind and other renewable sources.

This trend can be seen in new home construction in Maine, according to a baseline study done by Ridgeline.

The study shows a steep decline in the number of new homes heated with oil between 2015 and 2021, with 20 percent of homes now all-electric, with heat pumps or a combination of heat pumps and electric-resistance heat. Propane, however, accounts for the largest single share of new-home heating systems, 45 percent.

Propane’s popularity is good news for the Maine Energy Marketers Association, which represents many oil and propane dealers. The trade group has been pushing back against what it sees as a government-directed plan to “electrify everything” at the expense of consumer choice.


In an interview last summer with the Press Herald, the association’s president, Charlie Summers, said Mainers should be able to decide how to heat their homes. A survey done for the group found that nine out of 10 residents want state policies that let them choose how to heat their homes and businesses, choices that may include heat pumps but also other options. The group has been pressing political candidates this year to take a so-called Energy Choice Pledge, putting them on record as opposing any efforts to restrict how Mainers heat their homes and businesses.

On its website, the trade group urges caution about relying totally on heat pumps. Despite better technology, it says, “heat pumps are simply not ideal for climates like ours.”

Efficiency Maine disagrees, and will use the results from its mobile home pilot program to counter that view. But all homes are different. And it’s possible, Stoddard said, that some people will need or want supplemental heat sources. One example could be using an electric space heater to warm a remote, chilly room on the coldest days.

But overall, Stoddard said, the pilot confirms that heat pumps work in subzero temperatures. He hopes the demonstration will help clear up public misconceptions about the capabilities of the devices.

“Earlier generations of heat pumps stopped performing at extremely low temperatures,” he said. “It was reasonable for people to assume heat pumps, by themselves, couldn’t provide enough heat. But the new generation can do that.”

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