NEW HAVEN, Conn. — Iberdrola USA and UIL Holdings Corp. have closed on the Spanish firm’s $3 billion purchase of the Connecticut parent company of several local energy firms, including Central Maine Power Co.

Following the closing Wednesday, the combined company will operate under the name AVANGRID Inc., and it will trade on the New York Stock Exchange under the symbol AGR.

Connecticut regulators approved the deal last week.

James P. Torgerson, president and chief executive officer of UIL Holdings, became CEO of AVANGRID. The leadership team will comprise former executives of UIL and Iberdrola USA.

The deal combines eight electric and natural gas utilities with an $8.3 billion rate base and serving 3.1 million customers in New York and New England. The AVANGRID utilities will continue to operate in offices in Connecticut, Massachusetts, Maine and New York. Central Maine Power, which serves 600,000 homes and businesses in the state, is Maine’s largest electricity transmission and distribution utility. The company delivers about 9 billion kilowatt hours of electricity annually, representing about 80 percent of Maine’s annual consumer sales of electricity, according to the company’s website.