The company may also receive up to an additional $2.25 million over the next three years depending on performance.
Alterra will keep a 25.5 per cent stake in Dokie 1 and will continue to operate and manage the project.
GE Energy Financial Services holds a 49 per cent stake.
The project, west of Fort St. John in the northeastern British Columbia, includes 48 wind turbines.
"This transaction is a good growth milestone for us, providing us substantial capital to support our 2014 growth projects," Alterra chief executive John Carson said in a statement.
"Alterra's revenue, cash flow and owned generation capacity will all improve versus our pre-sale position as this capital gets deployed, resulting in overall accretion for our shareholders."
In addition to Dokie 1, Alterra operates a run-of-river hydro facility, two geothermal facilities in Iceland, and a geothermal plant in Nevada.