US Energy Systems (USES) has completed the $177 million (£93 million) acquisition and financing of the Knapton power station and related gas fields.
Knapton power station is based near Pickering in Yorkshire.
Asher Fogel, USES chief executive, described the purchase from Scottish Power as the first step in building his firm into a "significant participant" in the energy sector.
USES operates energy projects in both the US and UK.
The transaction includes the sale of the 42MW open cycle gas turbine to RGS Energy Limited (RGS), a subsidiary of USES, for £15.5 million in cash.
Scottish Power said it had also entered into "long-term" power purchase and gas supply deals with RGS.
John Campbell, energy wholesale director at the firm, said: "Securing this sale and these long term contracts allows us to recycle the value from this non-core asset into other investment opportunities and provides access to future gas reserves at an attractive price.
"The excellent sale price and the value of the long term contracts maximises shareholder value."