Ontario Power Generation Inc said on Tuesday its unit had entered a deal with affiliates of pipeline company TC Energy Corp to buy three natural gas-fired plants in Ontario for about C$2.87 billion ($2.18 billion).

TC Energy, formerly TransCanada Corp, will sell the 683-megawatt Halton Hills power plant, the 900-megawatt Napanee generating station that is nearing completion and TC Energy's 50% stake in the 550-megawatt Portlands Energy Centre.

Ontario Power has been building up its power assets through deals. In June, Ontario's largest electricity generator bought US-based hydropower company Cube Hydro for $1.12 billion and separately entered into a deal to buy the remaining 50% stake in the 560-megawatt Brighton Beach natural gas-fired power station from affiliates of Canadian Utilities Ltd's.

The latest deal, which is expected to close late-2019, is subject to regulatory approvals and Napanee reaching commercial operations, TC Energy said.

RBC Capital Markets is the financial adviser to Ontario Power.

Following the sale of the facilities, TC Energy's portfolio will include investments in six low-emission natural gas-fired power plants and the Bruce Power nuclear facility, where the company is undertaking a life-extension program and investing about C$2.2 billion by 2023.

TC Energy is set to report second-quarter results on Aug. 1.