Four months after it began supplying residential electricity for less, Electricity Maine is growing.

The Auburn-based competitive energy provider now has 21,000 customers, up from the several hundred it had when it was mentioned in the Sun Journal in August. This week the company, which serves as a kind of middleman between electricity suppliers and customers, announced it would supply electricity at 7.07 cents per kilowatt-hour in 2012, in part because it’s grown big enough to bargain with its suppliers for lower prices and in part to keep the promise it made to always stay lower than the “standard offer” residential customers get. 

“We’ve been wildly successful,” said Kevin Dean, who started the business with partners Emile Clavet, Kirk Nadeau and Peter Whitney.

In 2000, state law restructured the electric utility industry in Maine so utilities could no longer both supply and deliver electricity. The goal was to create a competitive market for power.

Maine’s major electric utilities — Central Maine Power and Bangor Hydro — began only delivering power. Consumers could contract directly with suppliers if they wanted, but to ensure every home and business had at least one good, automatic supply of power, the Maine Public Utilities Commission created a “standard offer.” As a result, the PUC now regularly accepts bids from suppliers, takes the lowest bid and makes the winner the default supplier at that bid price.

Maine’s large businesses started using competitive energy providers, or CEPs, to find supply prices that were lower than the standard offer. But because it cost a lot to market to residential customers and the profit margin for those small electricity users was slim, few CEPs opened to residential customers and virtually none advertised it.

This past summer, Electricity Maine opened for business. Its owners believed they had a way around the challenge of marketing to hundreds of thousands of residential customers: social media.

The company started with a fixed rate of 7.99 cents per kilowatt-hour, 6 percent less than the standard offer of 8.49 cents for CMP customers and 3 percent less than the standard offer of 8.25 cents for Bangor Hydro customers. The PUC recently announced that standard offer would drop in March. Electricity Maine dropped its rate as well, effective immediately. It will now charge 7.07 cents per kilowatt-hour, 4 percent less than the new standard offer of 7.4 cents for CMP customers and 0.4 percent less than the new standard offer of 7.1 cents for Bangor Hydro customers.

For CMP customers, Electricity Maine’s new rate is nearly 17 percent less than 2011’s standard offer.

“What we’re seeing is exactly what this competitive market was supposed to develop. It was supposed to make sure the customers have a choice and receive some of the benefits of a competitive market,” Dean said.

The company plans to increase its marketing in 2012 with TV commercials. It has also started a charitable program to donate money to area nonprofits based on its customer numbers.

Dean believes the company will continue to grow.

“It’s gradually building momentum,” he said.