The Alberta Utilities Commission has concluded that TransAlta Corp. deliberately timed power outages at power plants at peak times in order to drive up electricity prices.

The province's market surveillance administrator alleged that the Calgary-based company manipulated the electricity market by shutting down power plants in 2010 and 2011 to drive up power costs during periods when demand was high.

But the commission found that the market surveillance administrator did not prove allegations that TransAlta's compliance policies, practices and oversight were inadequate and deficient.

TransAlta denied all of the allegations, calling them "categorically false."