Two heating oil and energy companies announced Thursday that they will enter a growing market for wholesale electricity.

The South Portland-based Dead River Co. announced it will begin selling electricity alongside its other energy services in a market that has grown significantly more crowded in recent months.

The Portland Press Herald reported that C.N. Brown, based in S. Paris, also confirmed on Thursday that it plans to sell wholesale electricity, where prices have fallen faster than the standard-offer power rates from established electricity suppliers.  It’s the same market where Electricity Maine, based in Auburn, brought on 150,000 customers since 2011.

In mid-September, the Mass.-based fuel supplier Gulf Oil announcned that the company’s electricity-providing subsidiary — Gulf Electricity — will enter the wholesale electricity market in Maine, which also includes FairPoint Energy, a subsidiary of the telecommunications comopany, according to the Press Herald.