TransAlta Corp. says it's cutting its work force in its Canadian coal generating unit by 20 per cent as it works toward trimming annual costs by about $12-million.

The Calgary-based power producer started the cost-saving initiative in January and it says a "large part" of the savings are already being captured.

It incurred about $7-million in restructuring costs during the first three months of 2015.

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TransAlta's first-quarter profit fell nearly 45 per cent to $26-million from $47-million a year earlier.

Revenue for the quarter was $593-million, down 18 per cent from $775-million during the same period in 2014.