Eversource electricity customers in Massachusetts are getting a break on their monthly bills thanks to the corporate tax cut passed last month by Congress.

In November, state regulators approved a combined $37 million in rate increases for customers in the company’s eastern and western Massachusetts service areas. But since rates are based on the company’s costs, including federal taxes, Eversource said it will pass on ­almost $56 million in savings from the new tax bill to its 1.4 million customers in the state. “If taxes are reduced ultimately, costs are reduced and that benefits our customers,’’ Craig Hallstrom, Eversource’s president of Massachusetts electric operations, said in a statement on Wednesday.

Attorney General Maura Healey last month asked the Department of Public Utilities to recalculate the Eversource price hikes to factor in the new 21 percent tax rate for ­corporations, a drop from 35 percent.

Healey had opposed Eversource’s rate requests, which initially totaled almost $100 million. She wasn’t satisifed when the DPU approved the much lower increases.

“We are glad that Eversource has done the right thing by agreeing to lower its rates and we call on all our state regulated utilities to do the same,’’ Healey said Thursday in a statement.

A DPU spokesman declined to comment.

Eversource said that ­customers in Eastern Massachusetts will see a rate reduction of about $35.4 million, more than reversing the approved increase of $12.2 ­million.

For Western Massachusetts, rates will increase $16.5 million instead of the ­approved $24.8 million.

The reduction in the eastern part of the state is proportionally bigger because the cost of service is higher, ­according to Eversource spokeswoman Caroline Pretyman.

As part of its rate case, Eversource won permission to separately recover from ­consumers $45 million it plans to spend on infrastructure for electric vehicles, and $55 ­million to improve energy facilities on Cape Cod and Martha’s Vineyard.

Those amounts are not ­affected by the changes ­announced ­Thursday, Pretyman said in an e-mail.