Central Maine Power customers will see their electricity costs go down for the second consecutive year in 2021.

The Maine Public Utilities Commission announced Wednesday the results of its competitive bid process for setting next year’s “standard offer” supply prices, which will result in a nearly 12 percent drop on the supply portion of bills for residential and small business customers, to 6.45 cents per kilowatt hour.

It will be the second year in a row that standard offer rates have gone down. The new rates take effect Jan. 1.

The savings equate to a 5.1 percent reduction on a total residential bill, which includes the cost of supplying power as well as the cost of delivering it. For a customer using an average of 550 kilowatt hours a month, the savings are $4.70, or $56.38 annually. Put another way, a monthly bill of $91.38 would decrease to $86.68.

Medium-class customers will also see an average decrease of about 12 percent in the supply portion of their bill. A medium-sized business using 20,000 kWh a month will see savings of roughly $2,000 annually, the PUC said.

In a separate matter, Central Maine Power came in last place for the third year in a row in a national survey of business customers by J.D. Power & Associates. The ranking came at a time when overall business customer satisfaction with electric utilities has risen, the survey noted.

In a statement, CMP Executive Chairman David Flanagan said the utility was pleased that its ranking improved by more than 50 points over the previous year, but he acknowledged that the company has more work to do. He said CMP has made significant advances this year in areas important to business customers, such as reliability, responsiveness and community engagement.

The power rates announced Wednesday affect the majority of customers served by CMP who don’t choose to buy their electricity from a competitive supplier. The latest PUC figures show that 87 percent of homes and small businesses get their power via the standard offer.

Maine law requires the PUC to make sure electricity customers who don’t want to contract with retail suppliers have a default option.

Under Maine’s 21-year-old restructuring law, CMP and Versant deliver electricity, but don’t produce it.

Wholesale electricity prices in New England are driven primarily by the cost of fuel used to produce electricity and consumer demand, which is linked to weather and economic factors.

Natural gas-fired power plants generate roughly half of the electricity in the region and typically set the wholesale market price. The most recent data from ISO-New England, which operates the electric grid, show average natural gas prices are down 26 percent from September 2019, and the average electricity price is down nearly 3 percent.

Wednesday’s outcome mirrors the double-digit decreases announced a day earlier for customers of Versant, which serves much of eastern and northern Maine.

Versant’s residential and small business customers will see a 10 percent drop in the supply portion of their bills. That will equate a 3.6 percent cut in the total residential bill, the PUC calculated.

The cut will amount to a monthly savings of $3.41, or $40.95 annually. A monthly bill of $94.08 month will decrease to $90.67.

Multiple bidders submitted sealed proposals in the PUC’s annual competitive process for both utilities.