GAS UTILITIES IN MASSACHUSETTS spent a record amount of money in 2024 replacing leaky pipes through the state’s Gas System Enhancement Program, according to a newly released report from regulators, even as the actual miles of replaced pipes remained stubbornly flat since the program’s inception a decade ago.

The Department of Public Utilities, in its annual report to lawmakers on the state’s natural gas pipe system, found that the gas companies collectively spent $814.4 million to replace about 266 miles of leak-prone pipes. That’s by far the most the utilities ever spent since GSEP was created in 2014 and a nearly 40 percent increase in what was spent the year prior — despite the fact that the utilities replaced slightly fewer miles of leak-prone pipe than in 2023.

“The [utilities] have spent more money per mile, with the progress at remediating leak-prone pipe occurring at a pace that is largely unchanged from when the GSEP program was first initiated,” DPU said in its report.

The latest data on utilities’ work to replace leaky pipes, which emit the potent greenhouse gas of methane into the atmosphere, paints an even more damning picture of GSEP as costs balloon with few additional results — driving up ratepayer bills — and places recent reform efforts into greater context.

“We’ve just seen an absolute explosion in the costs of this program, and it appears to be far beyond inflation,” said Kyle Murray, Massachusetts program director at Acadia Center, an environmental research and advocacy nonprofit.

Massachusetts established GSEP in 2014 with the best of intentions: to create an incentive for utilities to quickly fix leaks across the state’s aging 21,000 miles of natural gas pipes and to provide Bay Staters who heat their homes and cook with gas a safer system and one that minimizes emissions.

Since then, though, the program has been beset by runaway costs and contention over how the state squares the circle of justifying hundreds of millions of dollars each year in investments into a gas system that Massachusetts is at the same time trying to cut off — and rather quickly.

The utilities have spent $6.2 billion on new gas pipes through GSEP, and spending through the program has increased by an average of 12 percent each year since 2015, according to the attorney general’s office, amid soaring material and labor costs. GSEP costs account for 8 to 11 percent of ratepayers’ monthly bills, the AG says.

The DPU stepped in last year to make key changes to address the climbing costs, including cutting how much utilities can recover from ratepayers through GSEP and incentivizing repairing lines instead of replacing them.

That DPU order came after negotiations over GSEP reforms proved to be a sticking point in the State House as lawmakers hammered out the 2024 climate bill.

State officials project the DPU order will reduce bills as Beacon Hill seeks to lower the cost of energy in Massachusetts, home to the country’s third-highest residential electricity prices. Regulators launched an investigation late last year at the urging of Gov. Maura Healey to review all charges on gas and electric bills.

Public outrage last winter over high ratepayer bills fueled Healey’s energy affordability bill currently under consideration in the Legislature. That has prompted fierce debate over what’s driven the rising costs, with some lawmakers even pushing to weaken the state’s 2030 climate commitments to halve greenhouse gas emissions compared to 1990 levels.

The GSEP issues have exposed the tough choices facing Beacon Hill as it manages an energy transition: continue to spend money on an expensive gas system, spreading out the costs over fewer people as households switch to electric, or begin to retire the network of pipes altogether in favor of technologies like geothermal and electric heat pumps — the latter of which entails up-front costs but promises savings down the line.

“If you do business as usual here, you’re going to keep throwing money at a system that is becoming antiquated,” Murray said. “And we’re going to stick an ever-declining ratebase with these costs, and then you are going to end up in an even greater affordability crisis. We’re going to be stuck with stranded assets if we don’t change the way we fundamentally do business here.”

Total gas leaks in the state have been cut in half since 2014, according to DPU’s report, with just over 9,000 pending leaks at the end of 2024, a nearly 15 percent decrease from the year prior.

But even then, the worst of the leaks, which require the most immediate action and represent an “existing or probable hazard,” increased from 37 to 40 from 2023 to 2024, as utilities battle the “Whack-a-Mole” of new leaks that emerge.

National Grid, the utility that operates the most miles of natural gas pipes in the state, was responsible for all 40 of these leaks not yet fixed at the end of 2024.