Nearly 9,000 households in eastern Massachusetts have had to make do without natural gas since mid-September, when an aging natural gas pipeline failed and set off a series of explosions and fires across the cities of Lawrence, Andover and North Andover.

Residents who relied on gas to heat their homes and cook their food won't have service again until mid-November at the earliest, according to Columbia Gas of Massachusetts. The company has 48 miles of pipeline to replace, and industry experts question whether it can meet even that timeline.

Environmental advocates say it's time to completely rethink the communities' energy systems.

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They are calling for a "green new deal" that would shift thousands of homes off natural gas and onto electric heating.

Columbia Gas has offered to reimburse "reasonable costs" for residents who lost gas service and want to permanently shift to another heating source. Some area residents, rocked by damage to dozens of homes and the death of one person from the gas explosions, have expressed concerns about ever returning to natural gas.

But environmentalists will have to work quickly. Columbia's offer to pay residents to cut ties with natural gas could also result in households moving backward—to high-polluting fuel oil.

"The choice is open to the customer whether they want to go back to the 19th century or go into the 21st century," said Nathan Phillips, acting director of the Sustainable Neighborhood Lab at Boston University.

The Possibility of Heat Pumps

Columbia Gas's offer opens the door for a number of options with emissions profiles that vary widely, including heat pumps, conventional electric heating, propane and fuel oil. Residents, or their landlords, also could decide to wait through increasingly cold weeks for the gas line to be rebuilt.

(Two weeks after announcing the plan, the company changed its reimbursement policy, making it less likely it would cover the full cost of electric heat pumps under new claims. Existing claims approved before Oct. 15 would be honored, spokesman Dean Lieberman said.)

One option Phillips and other sustainable development advocates are promoting is electric heat pumps—essentially air conditioners that can run in reverse in wintertime to heat rather than cool a home.

Heating a house with electric heat pumps requires roughly one-third the amount of energy as natural gas or other heat sources. And if the electricity comes from green energy, such as solar or wind power, the carbon footprint disappears.

Air source heat pumps look much like air conditioners. Credit: 51% Studio Architecture/CC-BY-SA-2.0

Heat pumps have been used for decades in moderate climates but improvements in the technology in the past five to 10 years have increased their efficiency, making them a viable option in colder locations, as well, said Larry Chretien, executive director of the Green Energy Consumers Alliance.

Unlike conventional heating systems, which burn natural gas or some other fuel to provide heat, heat pumps use fans, pumps, compressors and heat exchangers to draw heat out of the air and transfer that heat into the home. "There is a lot of heat energy in the air even in winter, and these heat pumps can capture that heat and move it indoors very efficiently," said Paul Eldrenkamp, a consultant on passive houses and deep energy retrofits who heads the DEAP Energy Group in Newton, Massachusetts.

Heat pumps, however, are typically more expensive to operate than furnaces or boilers that run on natural gas due to the current glut of low-cost, hydraulically fractured natural gas, though they are less expensive than oil or propane.

Eldrenkamp said the best solution for affected communities, especially Lawrence, a low-income community, would be to combine heat pumps with community-owned solar arrays paired with large-scale batteries.

"Let's take this opportunity to really bring these homes into the 21st century, not just for environmental reasons but for social justice reasons," Eldrenkamp said. "Let's not just switch them over to heat pumps, but let's get some solar panels in the neighborhoods and do the whole package."

To be a good candidate for heat pumps, homes must first be well insulated. Funding, including 100 percent of costs for low-income residents, is available for insulation through the state's energy efficiency program, Ken Stammen a spokesperson for NiSource, Columbia Gas's parent company, said, but lining up a required home inspection and contractors to do the work could create delays.

Massachusetts Attorney General Maura Healey has called on Columbia Gas to directly cover installation expenses for low-income customers, rather than just offering them reimbursements, so they don't face prohibitive upfront costs. She has also urged the gas company to provide a detailed timeline for replacements, to educate every customer on the availability of heat pump technologies, and to cover any additional costs if heat pumps are more expensive than their existing heating systems.

Chretien, of the Green Energy Consumers Alliance, cautioned that many of the affected homes, particularly those in Lawrence, have substandard electric systems and may require additional wiring before heat pumps can be installed. He added that homes with closed floor plans often require multiple heat pumps to ensure each room is properly heated, and that can increase costs.

"To get to an 80 percent carbon reduction by 2050 (the state's emissions reduction goal), we need to electrify everything including transportation heat and hot water," Chretien said. "Right now though, in 2018, in a hurry, it's a different story. It's complicated. Care has to be taken to make sure that it is in the customer's best interest."

Thinking Bigger, with Help from a River

Zeyneb Magavi, research director for the energy efficiency and clean energy advocacy group HEET and a member of Mothers Out Front, said the collapse of the gas system in the three communities calls for a bigger, more outside-the-box solution.

She is proposing a district heating system with an unusual heat source: the Merrimack River, which runs through Lawrence and skirts North Andover.

Just as heat pumps can draw heat from cold air, they can also pull thermal energy from water. A district heating system in Drammen, Norway, for example, generates 85 percent of the hot water needed to heat the city by drawing it from a cold-water fjord.

Magavi's aim is getting gas companies out of the business of selling gas and into selling heat.

Developing river-based district heating in Massachusetts would face a number of hurdles, including regulatory challenges. But the technology has a lot of promise, Magavi said. Cooling the Merrimack River by 1 degree could theoretically heat 100,000 homes, according to calculations by Mark Sandeen, chair of Sustainable Lexington, a committee appointed by town officials in Lexington, Massachusetts, charged with enhancing the town's environmental sustainability.

While such a conversion would take too long to address the immediate needs in the former mill towns, the ongoing outage could spark a larger transformation in a region that has long looked to its rivers as a source of energy and innovation.

"The Merrimack River Valley was the cradle of the industrial revolution," Magavi said. "It would be symbolically beautiful if it became the cradle of the next clean energy revolution."

Editor's note: This story was updated with Columbia Gas changing its reimbursement policy on Oct. 15.