State regulators on Thursday approved a new rate plan for National Fuel Gas customers that will freeze their delivery charges through September 2015.

The new rate agreement, which was hammered out in negotiations that concluded last December, calls for National Fuel to return $7.5 million to residential and business customers throughout Western New York to settle allegations that it earned excessive profits from its utility business in recent years.

Under the new rate plan:

• $3.72 million will be refunded to residential customers, with those consumers receiving refunds that will average $7.74.

• $1.77 million will be refunded to commercial customers, with refunds averaging about $31.43, although that will vary depending on usage.

• $1.75 million will go toward weatherization upgrades for low-income residential ratepayers, which will be administered by the state’s EmPower program. The program provides funding for such things as new doors, energy-efficient windows and insulation.

• $250,000 will fund a furnace replacement program for recipients of the Home Energy Assistance Program.

• Qualifying low-income customers will receive an additional discount of $12.50 per month on their winter heating bills from January to May over a three-year period beginning next year.

The rate plan approved by the state Public Service Commission mirrors a settlement that was hammered out in December during negotiations between the company and six groups representing residential and commercial customers. National Fuel’s delivery rates have not increased since 2008.

Karen L. Merkel, a National Fuel spokeswoman, described the rate plan as “a fair and reasonable rate plan that will provide benefits for all stakeholders.”

National Fuel’s 516,400 customers will receive their refunds in the form of a credit that will be applied to their bills in June, Merkel said.