The urgency to act on the climate crisis has local environmental groups calling for immediate steps to change how Rhode Island heats its homes and businesses.

One of the primary emitters of greenhouse gases is the burning of natural gas and oil to heat buildings and create hot water. The so-called “heating sector” in Rhode Island produces a third of the state’s 11 million metric tons of carbon dioxide equivalents released annually, and will do so for decades to come without significant changes.

A central recommendations in a recently released report called Heating Sector Transformation in Rhode Island suggests supplanting traditional gas and oil boilers and furnaces with electric-powered heat-source pumps.

Heat pumps have been around for decades, but are gaining popularity as an efficient way to regulate temperature, especially as wind and solar energy continue powering the electric grid with lower-emission energy.

One eye-popping statistic, however, is the amount of electricity that will be required to run a heating sector dominated by heat pumps. When heating needs are combined with a transportation sector that runs electric cars and trucks, the electricity demand could, during cold snaps, triple the amount of power generation used now.

Heat pumps are ideal for moderating temperature changes that stay within a range close to the desired interior temperature. But air-source heat pumps, in particular, work extra hard, requiring more electricity the further temperatures move from the mean. During extreme cold, temperatures can drop 70 degrees or more below the desired interior temperature. Whereas, in extreme heat, temperatures typically increase no more than 30 degrees above desired interior temperatures.

That said, heat pumps are becoming more energy efficient and gaining use in many cold regions, such as Maine, where oil generates most of the heat, and electricity is relatively inexpensive.

Heat pumps can be expensive, especially ground-source heat pumps, which before rebates and incentives average about $30,000. Much of the cost comes from the excavation required for installing a ground loop. But these geothermal systems are typically more energy efficient because they moderate using the temperature underground, which is a constant 50 degrees. Air-source heat pumps, which moderate using outside air, are less expensive to purchase — they start at about $2,000 to buy and install — but they must manage greater temperature swings and thereby cost more to run. First-time owners of air-source heat pumps are typically surprised by the jump in their electricity bills. That cost, however, that should be offset by lower gas and oil bills.

“Unfortunately, the downside of heat pumps is that they have higher upfront costs,” said Dean Murphy, an economist and consultant with The Brattle Group, the Boston-based group that authored the report.

Ground- and air-source heat pumps are two of four options outlined in the 91-page report. So-called “renewable gas” and “renewable oil” are the others. They are “renewable” because they use renewable power to produce a synthetic fuel or create the chemical reaction to produce hydrogen. Plant-based fuels, landfill gas, and woody biomass are considered renewable fuels that can power the heating sector and the transportation sector.

Renewable fuels allow homeowners to keep their oil and gas boilers and have the fuel delivered through existing pipelines and fuel trucks. But these fuels have their drawbacks. Producing biofuel stock could strain the food supply by displacing crops in order for plant-based fuels to be grown on a large scale. Making renewable fuels may also emit greenhouse gases through lifecycle emissions: power generation, transportation, and transmission leaks. They could be more expensive to manufacture and ultimately buy than fossil fuels. Biodiesel, which blends vegetable and cooking oils with other carbon fuels, contributes to lower emissions but, like landfill gas, it’s limited by the volume of feedstock to achieve scale.

“Waste biofuels are typically cheapest, but they are byproducts of other processes and thus have limited supply,” according to The Brattle Group.

Despite the wide range of potential costs and drawbacks, the report doesn’t rule out renewable gas and oil as part of the state’s future heating solution.

The report found that modest energy-efficacy upgrades, such as air sealing, insulation, and weather stripping, are effective at bringing down heating costs and emissions, and they should continue. But deep energy retrofits, such as re-engineering walls and replacing windows, could be cost-prohibitive. And even with subsidies, they might be not be cost-effective, given the old and idiosyncratic building designs found in Rhode Island. About 36 percent of the state’s residential buildings were built before 1950. Another third was built between 1950-1980.

The report also addresses a practice known as “district heating,” which supplies heat through smaller centralized neighborhood or campus heating systems. They run on hot water, steam, or ground-source heat pumps. They were first used in former communist nations and today are used by Scandinavian countries and to a smaller extent in the United States on college campuses and in urban neighborhoods. They are highly efficient and cost-effective, but can be a challenge to build and maintain in societies that emphasize individualism and private property like the United States.

The Heating Sector Transformation in Rhode Island report was created through a July 2019 executive order from Gov. Gina Raimondo as an approach to meet the state goal of an 80 percent reduction in greenhouse gases by 2050.

There are no specific next steps, except that, according to a state press release, the report’s policy principles will “encourage the state to seize natural investment opportunities, implement ‘no-regrets’ investments, continue deployment of nation-leading energy efficiency programs, and ensure that electric- and gas-distribution system upgrades are ‘future-proofed’ to enable decarbonized heating solutions at scale.”

The day after the April 22 report was released, four environmental groups signed a letter calling for swift action to adopt policies and programs “that the state can begin implementing aggressively right now for maximum impact.”

Those actions include promoting the adoption of heat pumps and continued use of rebates and other incentives to encourage purchases. They urge passing bills (S2165 and H7399) in the General Assembly that update and make legally enforceable greenhouse gas emission-reduction targets. They say another bill is needed to increase to 100 percent the Renewable Energy Standard, which mandates the amount of renewable power sent to the regional electric grid. Lastly, they say the state should take aggressive steps to implement energy-efficiency efforts.

“The time for small pilots of these policies has passed: we need to rapidly scale up each of these strategies immediately, while simultaneously continuing to innovate with new policies and technologies,” according to the April 23 letter from the Acadia Center, the Conservation Law Foundation, the Green Energy Consumers Alliance, and The Nature Conservancy.

The environmental groups also criticized the report for failing to address equity, which is demonstrated by The Brattle Group’s focus on singe-family homes.

The letter opposes the use of manufacturing methane and running it through existing pipelines and fossil-fuel infrastructure, saying it increases emissions while creating health and safety risks.

“Our current gas infrastructure is old and leaky,” according to the two-page letter. “Creating methane out of new sources and injecting it into our current infrastructure would continue to release this potent greenhouse gas into the atmosphere at unacceptable rates. Leakage of methane from our state’s gas infrastructure is a massive contributor to overall state emissions, and it is simply not possible to achieve even the state’s existing greenhouse gas reduction goals while these leaks continue. The cost to substantially overhaul our infrastructure to prevent leaks has already proven to be cost prohibitive, before accounting for the increased cost of the manufactured fuel itself.”

The environmental groups suggested making decisions based on science and data.

“The science of climate change is clear and unequivocal. To prevent the worst effects of climate change — effects already being felt in Rhode Island — we must decarbonize our economy by 2050, and the state needs to act quickly and decisively to benefit the generations to come,” according to the letter.