Eversource's new tariff affects about 500,000 natural gas customers in Massachusetts and, for example, increases a monthly gas bill from $250 to as much as $325.

National Grid's rate increase will affect about 950,000 natural gas customers in Massachusetts, increasing a monthly bill of $250 to as much as $282.50, for example.

The increases are effective immediately.

National Grid attributed most of its rate increase to the cost of Mass Save, the federally mandated energy efficiency program funded by monthly surcharges on ratepayers' bills. The program's budget is to be increased by 25 percent.

In a statement, National Grid said the overall increase included an increase of about 1.5 percent to cover the cost the company pays for the gas it supplies to its customers and that the remaining 9.5 to 11, 5 percent can be attributed to costs “related to energy efficiency programs”. ”

Eversource also said one of the components of the rate increase was the cost of paying Mass Save, but an Eversource spokesman would not say how much of the total requested rate increase was related to Mass Save.

In a statement, Eversource said Mass Save aims to save ratepayers money in the long run.

“Customers’ participation in the nation’s leading Mass Save program and access to benefits reduce customers’ bills every day,” the statement said.

“Without these programs, bills would be higher and household budgets would be strained,” the statement said. “The energy that a customer never uses leads to real savings.”

Managed by a consortium of utilities, Mass Save has been providing home energy audits and thousands of dollars in rebates for more than a decade to incentivize ratepayers to take steps like weatherizing their homes to reduce energy use and their carbon footprint.

Late last month, the Healey government announced its support for a plan to increase the Mass Save budget by about 25 percent, from $4 billion for the three-year period ending at the end of this year to $5 billion for the three-year period ending in 2025 until 2027.

The new plan was recently approved unanimously by a 14-member Energy Efficiency Advisory Council chaired by a representative from the Healey government's Department of Energy Resources.

Under the new plan, Mass Save aims to weatherize 184,000 homes, including about 75,000 low- and moderate-income households and 51,000 rental units, and support the installation of heat pumps in more than 119,000 homes, including 23,000 low- and moderate-income households Rental units.

In an Oct. 24 statement, Gov. Maura Healey said, “Massachusetts consistently ranks first in the nation when it comes to energy efficiency. “This new three-year plan will take Mass Save to the next level.”

A DPU spokesman said the regulator is “pursuing every opportunity to keep rates low for Massachusetts residents and families.” As gas prices continue to fluctuate through the winter, the department has taken steps to increase rebates for customers and transition to promote more stable clean energy sources and away from volatile fossil fuels.”

A Mass Save spokesman said the state Department of Energy and Environment dictates the level of reductions in greenhouse gas emissions statewide under each three-year Mass Save Plan, as required by law.

The attorney general's office, which serves as a taxpayer advocate, also praised the new Mass Save plan.

“This plan will deliver significant, cost-effective benefits to Massachusetts residents, reduce energy burdens for thousands of homes and make real progress in transitioning our state to clean heating technologies,” said Liz Anderson, chief of the Energy and Ratepayer Division of the Attorney General's Advocacy Group.

Utilities charge their customers for both delivery and delivery of natural gas, with Mass Save included alongside other delivery costs, such as infrastructure maintenance.

On the supply side, utilities generally charge their customers what it costs them to purchase natural gas. The cost of natural gas has generally remained stable after falling following a huge spike triggered by Russia's invasion of Ukraine in early 2022.

In its latest report, the U.S. Energy Information Administration said it expects natural gas prices in the Northeast to rise 1 percent compared to last year.

“In general, we expect relatively little change in energy bills for much of the country this winter compared to last winter, as lower energy prices largely offset colder weather,” EIA said.

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