TransAlta will undertake an independent review of its practices following a ruling that says the company timed power outages to drive up electricity prices.

The Alberta Utilities Commission ruled the company took plants offline at peak times for maintenance in 2010 and 2011. The commission could fine TransAlta up to $1 million for each day it shut down a power plant, which will be determined at a future proceeding.

In its quarterly earnings statement this morning, TransAlta's President and CEO says the company was surprised by that ruling. Dawn Farrell says the actions that led to this case were stopped almost five years ago.

"We recognize our responsibility to ensure confidence in Alberta's electricity system," she said in a release. "We stand by the need for full and fair competition and look forward to working with the province and the AUC to address these questions squarely and openly."

She says the company will undertake an independent review to ensure its practices comply with Alberta standards, which will be made public.

There is no mention this morning about whether the company will continue to look at taking the case to the Alberta court of appeal, as it had said in an earlier statement.

This is not the first time TransAlta, which is based in Calgary, has been in hot water over price fixing.

Last year, it paid a nearly $150-million settlement after allegations were raised that it manipulated the electricity and natural gas markets during California's energy crisis 15 years ago.

In 2011, the company admitted it had manipulated electricity imports, driving up prices so that consumers had to pay an extra $5.5 million for power.​