This article was originally published by Canary Media.

A hefty chunk of U.S. emissions comes from the energy used to heat buildings. That means millions of homes must be converted to electric heating in order to meet climate targets. 

In Colorado, a 2021 law spurred the state’s largest investor-owned utility to produce a plan that could transition a lot of homes to clean heating — and fast.

Xcel Energy’s Clean Heat Plan was approved this May. It directs more than $440 million over the next three years mainly to electrification and energy-efficiency measures that are meant to reduce reliance on the gas system and cut annual emissions by 725,000 tons.

The utility, which provides both gas and electricity to its customers, filed an initial plan that included proposals to spend heavily on hydrogen blending, biomethane, and certified natural gas. But after strong opposition from clean energy advocates who say these routes do not represent viable pathways to decarbonization, those proposals were reevaluated. Following a motion filed by the Sierra Club, Natural Resources Defense Council, and others last November, Xcel amended its original plan filed with the Colorado Public Utilities Commission.

Now the majority of funds will go toward building electrification and energy efficiency, which the commission found to be the ​“most cost effective and scalable ways to reduce emissions from burning gas and buildings, both in the short run as well as in the long term,” said Meera Fickling, building decarbonization manager at Western Resource Advocates.

Electrification efforts will primarily take the form of incentives that make it cheaper for customers to switch gas heating appliances to electric heat pumps. The incentives can be combined with federal electrification tax credits and extend to all-electric new construction as well. One-fifth of the program’s funding is earmarked for low-income customers. The plan’s funding is roughly three times the $140 million that the Inflation Reduction Act allocated to Colorado for similar measures.

The utility forecasts gas sales to decline by 14 percent between this year and 2028, The Colorado Sun reports.

While many states have incentives and rebates available for upgrading to energy-efficient appliances and heating solutions, Colorado specifically directs its gas utilities to lead those programs — and holds them accountable for contributing to the state’s climate goals.

That’s why Xcel’s new clean heat program will be ​“a test case of a utility-led model towards decarbonizing the gas distribution system,” Fickling said. ​“It really serves as a model — a nationwide model — for how gas utilities can allocate resources to decarbonize their system in the long term.”

From state laws to utility plans 

Colorado’s push to clean up home heating started three years ago with the Clean Heat Law, which requires gas distribution utilities to create concrete plans to reduce their greenhouse gas emissions 4 percent below 2015 levels by 2025 and 22 percent by 2030. Xcel’s recently approved Clean Heat Plan will carry the utility through 2027, and the utility must propose a new plan in the coming years to meet the next target.

“I expect the next plan to really take a close look at the 2030 target and the trajectory to achieve it,” said Jack Ihle, regional vice president of regulatory policy at Xcel.

The Clean Heat Law was the first of its kind in any state, Fickling said, though others have since taken steps to curtail the climate impact of heating.

Following Colorado’s 2021 law, in 2023 Vermont passed the Affordable Heat Act to reduce emissions from home heating, and Massachusetts drafted similar legislation. This year, Illinois and New Jersey have both introduced bills with clean heating and decarbonization standards.

In Minnesota, the state’s largest gas utility just received approval for a five-year, $106 million plan to reduce its emissions following the state’s 2021 Natural Gas Innovation Act. The utility, CenterPoint Energy, says the plan would ​“reduce or avoid an estimated 1.2 million tons of carbon emissions over the lifetime of the projects,” though advocates have criticized the approach.

But utilities in Colorado ​“have a lot more flexibility in terms of the portfolio that they propose,” said Joe Dammel, manager of carbon-free buildings at RMI. While Xcel can prioritize energy efficiency and electrification in Colorado, Minnesota’s Natural Gas Innovation Act requires gas utilities to produce emissions-reduction plans that spend at least half of their budgets on alternative fuels like renewable natural gas, which can still heavily pollute. In Colorado, a much smaller amount is dedicated to alternative fuels; only around $10 million out of the $440 million can be spent on renewable natural gas and recovered methane, and all projects must specifically be approved by the commission.

Another difference between the two recently approved plans is that Xcel delivers gas and electricity to about 1.5 million customers in Colorado, which gives it an opportunity to counterbalance lost gas revenue with increased sales from its electricity business. 

Meanwhile, CenterPoint serves gas to about 910,000 customers but has no electricity customers. That gives it fewer opportunities to make up for losses from its gas business driven by electrification mandates, and more incentive to prioritize the use of alternative fuels delivered through the pipelines it owns — and not electrification.

Investing in 100,000 heat pumps 

Now that the funds have been approved, Xcel is waiting on a final written order from regulators, which should arrive later this month. From there, it will start implementing the plan and work on defining rebate levels and informing customers on how to access incentives.

The details are still being decided, but customers will likely need to pay first and then get reimbursed later, as is the case for many current rebate programs, said Emmett Romine, vice president of energy and transportation solutions at Xcel. Customers would also get higher rebates if they choose more advanced technologies, like high-efficiency cold-climate heat pumps.

Beyond educating customers, the company is putting workforce-training plans together to ensure there are enough heat-pump installers ready to help customers convert. Xcel is also working with distributors and manufacturers ​“to make sure that there’s a supply chain that will come to Colorado when we stimulate demand,” Romine said.

The plan represents a significant step up from Xcel’s current pace of upgrades. ​“The goals are really aggressive,” Romine said. ​“When you look at the number of heat pumps and the number of water heaters we’ve got to contemplate getting into homes, it’s an enormous amount of work.” Currently, Xcel does around 10,000 rebates a year for traditional gas furnaces. Now, it’s aiming to do 20,000 heat-pump conversions this year and just under 100,000 total by the end of 2026, Romine said.

That supercharged effort won’t come without costs. Ratepayers will see electricity rates go up by 1.1 percent and gas rates rise by 7 percent over the next four years due to the plan. But advocates say it’s worth it to avoid pouring money into a gas system that must be phased out — and that the climate benefits outweigh the upfront costs. Even without the Clean Heat Plan, Xcel projected it would need to increase base rate revenue by 32 percent between 2023 and 2030, The Colorado Sun reported.

Colorado’s plan ​“is a very good example of needing to pursue both sides of the equation at the same time — decarbonization, electrification — but at the same time ensuring that we’re starting to shrink and eliminate unnecessary investments in the gas system,” said Alejandra Mejia Cunningham, senior manager of state buildings policy at the Natural Resources Defense Council.

The Public Utilities Commission has encouraged Xcel to report its progress by 2026, ahead of the legally mandated schedule, Ihle said. Advocates will be watching closely to see how it all plays out.

“We’re gonna have to make sure that we’re seeing the results of that in terms of participation, customer satisfaction, and ultimately emissions and cost reductions,” Dammel said. ​“There’s going to be a lot of utilities across the country following this.” 

Xcel Colorado’s new clean heat plan is a big deal. Here’s why. is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.

This article is a paid promotion and the Energy News Network is not responsible for its contents.

The need to prioritize the installation of heat pumps in California’s low-income households is clear.

California’s Fourth Climate Change Assessment devoted a separate report on the challenges for low-income residents in the San Joaquin Valley and the resulting health implications. Affordable air conditioning is likely at the top of the list of health needs for the vulnerable in the San Joaquin Valley, where weather regularly exceeds over 100 Fahrenheit in the summer and fall.

“Some residents living in these homes are disabled, need regular medical attention, and are unable to work,” a program implementer noted in a pilot report update on San Joaquin Valley, reporting on the conditions that program recipients had endured prior to the heat pump installations. “Ethically, these customers need HVAC systems to live comfortably and cannot be overlooked.”

Yet ensuring that these same communities benefit from rebate programs to encourage heat pump installations is more complex.

It turns out that for low-income residents, participation in a rebate program can require thousands of dollars of additional out-of-pocket costs, relative to richer households, because the homes tend to be older, the electricity is more likely to need upgrades, and there are often additional modifications or infrastructure improvements required — such as replacing water damaged flooring or walls from leaks — to provide the power. These costs, for additional wiring and other critical work, are typically either only partially or not covered by most rebate programs.

TECH Clean California, a statewide initiative to accelerate the adoption of clean space and water heating technology and put California on a path to carbon-free homes by 2045, has identified these additional costs as a key barrier to introducing heat pumps into lower-income homes.

“If you are a lower-income or harder-to-reach person, you’re probably not going to participate in a program that requires you to do a $20,000 HVAC replacement that you can’t afford,” said Sandy Laube, an energy efficiency policy researcher at Energy Solutions, the program administrator of TECH Clean California.

To address this roadblock, TECH Clean California provided funding for an already existing program, the San Joaquin Valley Disadvantaged Community Pilot Project. The pilot is part of California’s broader effort to assess the economic feasibility of helping these residents reduce their energy costs by replacing certain appliances with electric ones. The findings will be used to determine how best to meet the State’s broader goals for addressing climate change and reducing the disproportionate climate burden these communities bear.

TECH Clean California, which has committed 40 percent of its incentive funding to income-qualified customers, has learned that working with other partners in equity work helps leverage that commitment even further.

For this effort, TECH Clean California experimented with encouraging greater participation from interested households, many of which were budget-constrained.

The San Joaquin Valley Disadvantaged Community Pilot program had funded the installation of heat pump systems into roughly 279 qualifying low-income homes in the San Joaquin Valley, but due to restrictions in how funding can be used, there is a $5,000 minor home repair remediation cost maximum. This put some of the needed repairs out of reach for would-be program participants.

TECH Clean California was able to provide enough additional incentive funding to expand the San Joaquin Valley Pilot, so that it could reach more residents. In fact, TECH Clean California successfully helped fund remediation work in 89 additional homes. “We saw that many of these lower-income households were not going to be able to participate and get the broader benefits of renewable power in their home,” Laube said. “We wanted to be equitable in how we are spending the incentive money, which has meant finding ways to include groups that would normally not participate.”

This additional TECH Clean California funding covered home repair expenses, trenching, and other infrastructure costs, bridging the gap between what the utility was able to fund through its program and what the end customers needed to install the new electrification equipment. As a result, eligible customers had no additional out-of-pocket expenses.

“The additional TECH Clean California funding ended up being very important,” said Jose Landeros, the Director of Energy Programs for Proteus. “If it had not been for those additional funds for the remediation, many of these customers would not have participated.”

The needed work which TECH Clean California funded were a subset of homes that PG&E’s Building Electrification program had identified as needing heat pump water heaters. For these homes in San Joaquin Valley, the preparatory work for installation in a 2022 pilot project revealed a broad range of preliminary repair issues that first needed to be addressed.

Many of these homes needed to relocate the new heat pump systems water heater to the exterior of the home, requiring the installation of a metal enclosure for protection from weather or other damage.

Several residences in the San Joaquin Valley also required panel upgrades to support the added load of the new electrical equipment.

“It costs more money to electrify low-income households,” said Rachel Etherington, an energy transition strategist with the Ortiz Group, who worked with the San Joaquin Valley community in facilitating heat pump installations. “You only know how bad it is when you’re on the ground. “There’s no pavement for example. You can’t put machinery on dirt. You must revert to manual trenching, so that’s a significant labor cost. And every single home needed an electrical panel upgrade. It gives you an understanding of why it’s such an interesting project, like the pioneer of low-income implementation.” However, these kinds of upgrades will have further benefits for customers down the road, providing the basis for further electrification.

“A 200-amp panel gives low-income customers a better availability of power for the future, meaning that if they do have to get an electric car, they now have the capacity to be able to put an EV charger on their house,” said Lyal Ray, a quality production manager for Synergy Energy who was actively involved in many of the installations for San Joaquin Valley. “They have the capacity to put battery storage that is provided for low-income housing.”

It’s these kinds of hidden costs that are proving to be a barrier for lower-income families to access the benefits that electrification technology such as heat pump water heater HVACs can provide. 

“Without TECH Clean California funds, 89 of these households would not have been able to participate, elderly residents who require electricity all day, residents on dialysis machines,” Etherington said. “They required a significant amount of infrastructure upgrades. But at the end of the day, these are people’s homes, and those TECH Clean California funds created a huge quality of life improvement for those households.”

Written by Emily Pickrell. For more information about this and other projects, please visit TECH Clean California’s Annual Report at techcleanca.com. The report highlights learnings and accomplishments through the initiative’s statewide focus and collaboration. The guiding principle of TECH Clean California puts the state on a pathway to six million heat pumps by 2030 and carbon-free homes by 2045.

Commentary: Encouraging heat pump technology for San Joaquin Valley residents is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.

A new analysis says Vermont is not on track to meet its 2025 target for reducing greenhouse gas emissions, with declines in thermal fossil fuel use driven mostly — though not entirely — by warming winters. 

The study, released last month by the Vermont nonprofit Energy Action Network, also shows signs of progress: Though rising temperatures are still the main driver of lower heating fuel sales, weatherization and electric heat pump adoption are starting to have a greater impact.

“Vermont’s efforts… are, ironically, being aided by the very global heating that we are working to do our part to help minimize,” the study says. “Relying on warmer winters to reduce emissions from fossil heating fuel use is not a sustainable strategy. … What [the warming trend] means for temperatures — and therefore fuel use — in any given year is still subject to variation and unpredictability.” 

Like most other New England states, Vermont relies heavily on heating oil and, to a lesser degree, propane and utility gas, to heat buildings. This makes the building sector a close second to transportation in terms of the biggest contributors to planet-warming emissions in Vermont and many of its neighbors. 

Vermont’s statutory climate targets, adopted in 2020, aim to cut these emissions by 26% below 2005 levels by next year, with higher targets in the coming decades.

“It’s technically possible” that Vermont will meet its thermal emissions goal for next year, but “at this point, primarily dependent on how warm or cold the fall and early winter heating season is at the end of 2024,” EAN executive director Jared Duval said. The transportation sector would need to see a nearly unprecedented one-year decline.

On the whole, EAN says it’s “exceedingly unlikely” that Vermont will meet its 2025 goal. 

Warmer winters ‘not the whole story’

EAN found that heat pump adoption and weatherization are not happening fast enough, and what’s more, the current trend sets Vermont up for a Pyrrhic victory at best: Rising temperatures in the upcoming heating season would have to be at least as pronounced as in last year’s record-warm winter in order to reduce fuel use enough to meet the 2025 target for the thermal sector. 

Either way, warming alone won’t get Vermont to its 2030 target of a 40% drop in emissions over 1990 levels, Duval said. The state wants to end up at an 80% reduction by 2050. 

“The only durable way to reduce emissions in line with our science-based commitments is to increase the scale and pace of non-fossil fuel heating solutions and transportation solutions,” he said.

The EAN study found that fuel sales tend to decline alongside heating degree days: a measurement of days when it’s cold enough to kick on the heat. Vermont is seeing fewer of these days overall as temperatures warm. 

“The reduction in fossil heating fuel sales as winters have been warming is not surprising,” Duval said. “Historically, fossil heating fuel use and therefore greenhouse gas emissions have largely tracked with heating demand, with warmer winters corresponding with less fossil fuel use and colder winters with more fossil fuel use. The good news is that’s not the whole story.”

In recent years, he said, fuel sales have begun to “decouple” from the warming trend to which they were once more closely linked. From 2018 to 2023, EAN found that Vermont fuel sales declined 12% while heating degree days only declined 8%. 

“Fossil heating fuel sales are declining even more than you would expect just from warmer winters alone,” Duval said. “And that’s because many non-fossil fuel heating solutions are being adopted.” 

Upgrades needed to accelerate progress

From 2018 to 2022, EAN found, Vermont saw a 34% increase in weatherization projects and more than 50,000 more cold-climate heat pumps installed in homes and businesses, with a 3.3% increase in the number of homes that said they use electricity as their primary heating fuel. 

The upshot: The number of cold days explains 50% of Vermont’s declining fuel use from 2018 to 2023, while heat pump growth explains as much as 28% and other efficient upgrades explain a further 15%. The remaining 7% of the decline couldn’t easily be broken down and could partly be from people shifting to wood heat during periods of high fuel prices, Duval said.

“In order to achieve thermal sector emissions reduction targets without relying primarily on an abnormal amount of winter warming, significantly more displacement and/or replacement of fossil heating fuel… will be necessary,” the study says. Upgrades like heat pumps will lead to more sustainable emissions cuts, it says, “no matter what the weather-dependent heating needs in Vermont will be going forward.” 

EAN is nonpartisan and doesn’t take policy positions, but research analyst Lena Stier said this data suggests that expanding Vermont’s energy workforce and tackling heat pumps and weatherization in tandem would spur faster progress on emissions cuts, while keeping costs low.

EAN based its estimates of fuel use and emissions impacts from heat pumps on the official assumptions of a state-approved technical manual, which Duval said may be overly optimistic. But Stier said the reality could differ.

“We’ve heard anecdotally that a lot of people who have installed heat pumps in their homes… are kind of primarily using them for cooling in the summer,” she said. “So our kind of assumption is that, in reality, it would be a smaller share of that (fossil fuel use) reduction coming from heat pumps.” 

While fuel use declined overall in the study period, he said this came mostly from people using less heating oil specifically — propane sales actually increased in the same period.

Duval noted that propane is cheaper than oil on paper, but actually costs more to use because it generates heat less efficiently than oil does. 

“Once you look at that, then heat pumps become that much more attractive,” he said.

Editor’s note: This story has been updated for clarity.

Study: Vermont’s warming winters ‘not the whole story’ for declining fossil fuel use is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.

Environmental agencies in nine states will work together to reduce planet-warming carbon emissions by making electric heat pumps the norm for most new home HVAC equipment sales by 2040. 

The memorandum of understanding, spearheaded by the inter-agency nonprofit Northeast States for Coordinated Air Use Management, or NESCAUM, was released today and signed by officials in California, Colorado, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon and Rhode Island. 

While it is not legally binding and does not commit particular funding, the agreement calls for heat pumps to make up 90% of residential heating, air conditioning and water heating sales in these states by 2040. 

An interim goal of 65% by 2030 is based on last fall’s target from the U.S. Climate Alliance, a group of 25 governors, to quadruple their states’ heat pump installations to 20 million in the same timeframe. 

The residential sector is one of the top two or three contributors to greenhouse gas emissions in most of the East Coast states signing on to the agreement, driven in part by cold climates and a heavy reliance on oil and gas for home heating. Residential emissions rank far lower in the Western states participating.

In a press release, NESCAUM emphasized the harmful smog, haze and ozone driven by nitrogen oxide and particulate emissions from fossil fuel combustion, calling buildings “a hidden source of air pollution.” 

Senior policy advisor Emily Levin said states must move quickly to help residents replace these fossil-fired HVAC and water heating systems with heat pumps in time to limit the harms of global warming. 

“You may only have one more crack at these buildings between now and 2050, because these are long-lived pieces of equipment — they can last 10 or 20 years,” she said. “So we really can’t miss our opportunity.” 

Clear market signals

Matt Casale, senior manager of market transformation with the Building Decarbonization Coalition, said the new agreement’s market-share approach adds specificity to how states will meet existing, number-based goals for heat pump installations. 

“The idea is to send a clear signal to the market that heat pumps are the future of home heating and cooling, while reflecting the urgency with which we need to act to meet GHG emissions reduction targets,” he said. 

Manufacturers have called for this kind of “long-term signal,” said Levin — “they need to plan, they need to make significant investments.” She said agreements like this show companies that “this is the direction we need to go in” and that state governments are committed to helping make the transition happen.

“Greater demand for heat pumps will also put pressure on installers,” Casale added. “We will need policies that both grow and further develop the workforce. The MOU is a great opportunity to bring them in more directly, learn from them, and talk about their needs.” 

Under the new agreement, participating states will “collaborate to collect market data, track progress, and develop an action plan within a year to support the widespread electrification of residential buildings,” according to NESCAUM.

Afton Vigue, a spokesperson for the Maine Governor’s Energy Office, said taking advantage of consolidated industry data will help prevent another new reporting requirement for participating states and will help align with varying state metrics.

The states’ forthcoming action plan is expected to include emphasis on workforce development and supply chain constraints, which have tempered otherwise strong heat pump progress in states like Maine. 

“It really does focus on that element of driving the market and collaborating with manufacturers,” Levin said. “Right now, states don’t really necessarily know … how their heat pump market is developing. Creating systems to bring visibility to that, provide insights into that … it’s a really important element.” 

The agreement tees up annual reports on each state’s progress toward the 2030 and 2040 goals, and schedules a 2028 check-in about any necessary adjustments. 

Collaborative tools for affordability and access

“A greater focus on consumer education, workforce development, and affordability will be critical to the success of the transition,” said Casale. “This means getting the most out of the Inflation Reduction Act and other incentive programs, but we also need to answer the questions of how this solution best serves multi-family buildings, renters and others for whom purchasing a new system isn’t entirely within their control.” 

In the agreement, the states pledge to put at least 40% of energy efficiency and electrification investments toward disadvantaged communities — those facing high energy cost burdens or disproportionate pollution — in line with the federal Justice40 program, which underlies similar rules for the IRA.

Working through NESCAUM and other existing groups, the participating states will brainstorm tools for reaching these goals, potentially including funding for whole-home retrofits, building code enforcement and other uniform standards, data collection, research projects, use of federal resources and more. 

“It’s going to look a little different in every state,” Levin said. “But they’re committing to collaborate and to advance a set of policies and programs that work for their state to accomplish those broader goals.”

This could include adapting or building on each other’s approaches. Levin highlighted Maine and California as having successful models for consumer outreach and heat pump market coordination, and said Maryland has shown strong impact and ambition around clean building performance standards. 

Maine, which relies more on heating oil than any other state, is among the participants with existing heat pump goals in their climate plans. The state surpassed an initial target — 100,000 installations by 2025 — last year, and now aims to install 175,000 more heat pumps by 2027. 

Officials in Maine have said that heating oil use appears to be slowly falling in concert with increasing use of electricity for home heat. Vigue said the new agreement lines up with existing state goals and will help Maine “bolster our ongoing collaboration with other states, share experiences, and see where gaps may exist.” 

Nine states pledge to boost heat pumps to 90% of home equipment sales by 2040 is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.

New state incentives are pushing Mainers to adopt “whole-house” heat pump systems, making efficient electricity the primary home heat source and discouraging the secondary use of oil or gas.

Federal tax credits are still available for a wider range of heat pump installations, and the state offers rebates for low-income households to install a heat pump as a supplemental heat source. 

But the latest big rebate for families of any income in Maine, which has become a national leader in heat pump adoption, focuses on using this technology to heat and cool the user’s entire house — or close to it. 

“Customers are then able to turn off their old central furnace or boiler, relegating it to an emergency backup system,” said Michael Stoddard, the executive director of the state’s energy incentives agency, Efficiency Maine, in an email. “When that happens, (heat pumps) are able to meet their full potential.”

The agency’s new whole-house rebate program aims to help meet Maine’s climate goals. First rolled out this fall, the rebate was revised in recent weeks in response to criticism and confusion from contractors over its compliance rules. 

What are whole-house heat pump systems? 

A whole-house heat pump system — also called whole-home, or whole-facility in a space like a school or business — means that heat pumps are the go-to source of heating in the winter, with any supplemental sources used infrequently or as emergency backups.

To receive Efficiency Maine’s new rebate, which covers 40% of project costs up to a $4,000 cap for people of any income or more for those of lower incomes, a heat pump system must be sized to serve at least 80% of the home’s potential heating load, from shoulder seasons to the coldest day of winter.

Eben Perkins, the chief strategy officer with the Maine-based energy consulting firm Competitive Energy Services, said this is just one way of defining a whole-house heat pump in the grand scheme: For example, his company tends to look at how much heat pumps are serving a client out of the whole year, rather than on a day-to-day basis. 

What role do whole-house systems play in Maine’s climate goals?

Maine home heat targets are based on modeling of how many heat pumps and weatherization jobs it would take to offset the state’s top-in-the-nation reliance on heating oil and other use of fossil fuels in buildings, with statutory targets of cutting emissions 45% over 1990 levels by 2030 and 80% by 2050.

This sector, which includes schools, businesses and more along with homes and apartments, is second only to transportation in contributing to Maine’s emissions.

This past summer, the state hit an initial target of installing 100,000 heat pumps relative to 2019. Now, it’s working toward another 175,000 more units by 2027. Stoddard said the goal is to see 130,000 homes with one or two heat pump units by 2030, and 115,000 more with whole-house systems. 

“The efficiency levels of heat pumps can be two-X, three-X, four-X technology compared to a combustion system. So one, it’s just a good technology that keeps on getting better,” said Perkins. “Second, it gives you a pathway to actually fully decarbonize the upstream fuel source… That’s the pathway we need to really deeply cut emissions at the state (level).” 

Maine had about 580,000 households in 2022, per the U.S. Census, and about 56% of them use heating oil, according to federal data — slightly lower than in recent years, but still the highest rate in the country. 

The state aims to make its energy usage 100% renewable by 2040. 

Can you use fossil fuels alongside whole-house heat pumps? 

The answer is technically yes, but ideally no, at least under Maine’s new rebate.

As they switch to whole-house heat pumps, eligible customers are asked to turn their oil- or gas-powered furnaces or boilers and connected thermostats off or all the way down, and to cover the systems’ switches. They can still use these systems for hot water heating or in connection with an emergency generator.

This fall, Maine walked back an earlier requirement that old fossil-fired systems be disabled or disconnected from electrical service entirely, with locks on their switches, amid pushback from heat pump installers and fuel oil vendors about reliability and other concerns. 

Despite reverting the rebate to more of an honor system, Stoddard said avoiding supplemental fossil fuel use as completely as possible is key to maximizing heat pump benefits.

“Our research shows that the majority of heat pumps installed in Maine will save significantly less money and emissions when they are operated concurrently with a central furnace or boiler than when they operate alone,” he said. 

The rebate rules suggest “room heaters, a wood stove, or small space heaters,” Stoddard said, to cover up to 20% of the home’s heating load alongside the whole-house heat pump system.

Why does Maine focus on a certain approach to whole-house heat pumps? 

In theory, a whole-home heat pump system could have a range of configurations. But Efficiency Maine focuses its new rebates on heat pumps with one indoor unit per outdoor unit (which they call “single zone,” though contractors say this can have different meanings). These might be the customer’s first heat pumps, or they might add on to older units to make up that 80% heating overall capacity required by the state. 

Dave Ragsdale, the HVAC division manager at Maine-based ReVision Energy, said heat pumps need to be carefully tailored to a home’s needs to maximize their efficiency. 

“You really need to have the… capacity of your heat pump system match the heat load of the house as closely as possible,” he said. “To the extent you oversize a heat pump system, you’re creating a situation where it’s beginning to resemble, more and more, an old-fashioned heating system.” 

Traditional boilers and furnaces, he said, are almost always far oversized to the house’s heating needs — because they can be. “When you have a call for heat in a room, the thermostat tells the boiler, ‘we need heat,’ (and) turns the boiler on. It doesn’t matter how many (units of heat) that boiler is rated for — it’s only going to run for as long as it needs to to get heat to that room to satisfy that thermostat,” Ragsdale said. 

Heat pumps are different, he said: They perform best when they can run pretty much constantly and modulate their output in response to temperature needs. If a heat pump is sized to provide more heat than the house could ever need — or, say, if one outdoor compressor is sized to run heat pump heads in four rooms, though only one or two may be used at a time — it can lead to costly, inefficient “short-cycling.” 

“As soon as (the oversized heat pump) turns on, its capacity is way in excess of the load,” Ragsdale said. “So almost immediately, it floods the room with heat and then turns off, and then the room loses heat, and then it turns on again,” much like a traditional fossil fuel-fired system.

Ragsdale said this need for fine-tuning is why Maine’s rebate focuses on those one-indoor, one-outdoor, “single-zone” units — and why he suggests customers choose whole-house systems that meet just a tiny bit less than their home’s peak hypothetical heating load, ideally 99% or 99.6% of it. 

“That little adjustment is enough to bring the capacity of your system more in line with what you’re actually going to see throughout the course of the heating season,” Ragsdale said. 

If pushed to 100%, the system would be overpowered almost every day of the year, reducing efficiency and driving up costs. In the 99% design, the whole-house system is more efficient year-round and can use its supplemental sources to take the edge off and improve performance in the coldest weather conditions. 

Are whole-house heat pump systems right for every house? 

Getting the most out of a whole-house system requires careful customer education and for contractors to assess a home’s energy needs in great detail, Ragsdale said. Assessing air leaks and insulation needs with an energy audit can be a key part of this process. Ultimately, he sees houses with a more open floor plan and excellent weatherization as the best candidates for a cost-effective whole-house system.

“One thing is crystal clear… this whole-house model is not going to be applicable to every house you come across,” he said. “If there’s a house that’s broken up into a lot of small rooms, it’s probably going to be difficult to make a (whole-house) heat pump system work really well there.” 

The same goes for using existing ducts from a forced hot-air system to run heat pumps, accompanied by an air handler. Those ducts will need new insulation to safely carry cold air in the summer, which is a complex retrofit for an existing house. Even at best, Ragsdale said, “you’re losing a fair amount of (heat) in the distribution” relative to a ductless heat pump delivering its hot air more directly. 

But for people who may be unsure or ill-suited for the whole-house switch, Ragsdale emphasized that other heat pump configurations can still help vastly reduce fossil fuel use and costs, especially with state and federal incentives.

“Heat pumps still make sense, even a house that doesn’t have the perfect layout,” he said. 

He gave his own home as an example. It was built in the 1940s, with lots of small rooms. 

“I put one (heat pump unit) in my living room, which is the single biggest room, so I’m taking a big chunk out of my heat load even before I stop using my boiler altogether,” he said. “Most of that heat, frankly, in the shoulder seasons, managed to get its way around the house enough so that I was perfectly comfortable. 

“Only in a couple weeks out of the winter,” he said, “did I have to turn that boiler on to … take the chill off.”

Maine turns its heat pump focus to ‘whole-house’ systems that can all but eliminate fossil fuel use is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.