The total enterprise value of the deal amounts to $6.1 billion, including debt, Pattern said. Newswire Reuters reported the value of the transaction to be around $2.63 billion.
Shareholders will receive a cash consideration of $26.75/share, a 14.8% premium on Pattern Energy's 9 August closing share price — prior to rumours of a takeover.
CPPIB will also combine Pattern Energy and its sister company Pattern Development — currently backed by private investment firm Riverstone Holdings — in to "common ownership".
Pattern Energy CEO Mike Garland will continue to lead the combined company.
The transaction is expected to close in Q2 2020, subject to the required regulatory and shareholder approval.
Pattern has an operational wind portfolio of roughly 4.4GW spread across the US, Canada and Japan.
Coinciding with the purchase by CPPIB, Pattern also released its Q3 financial result, posting a net loss of $71 million, compared to a net loss of $31 million in the same period of 2018.
The firm's Ebitda was also down 19% to $65 million in the quarter due to lower earnings from operational projects as a result of "increased corrective maintenance expense".
The amount of electricity sold increased from 1.62TWh to 1.74TWh in the quarter, Pattern said.