The windfarm, in East Renfrewshire near Glasgow, is made up of six turbines and has a capacity of 12MW.
Scottish Power Renewables acquired the £23 million project from RWE Npower Rnewables in December 2011.
Simon Christian, UK managing director at ScottishPower Renewables, said: “The rigourous timeframe in which Middleton Windfarm was delivered, just under one year, highlights the industry leading expertise of our internal team.
“Since the project entered its operational phase earlier this year, it has been generating cleaner, greener power, contributing towards Scotland’s carbon reduction targets.”