EDMONTON -- Electricity rates in Alberta would be capped under legislation the provincial government introduced Tuesday, a move it says will protect customers from major price spikes.

The government says the four-year cap of 6.8 cents per kilowatt hour is expected to be in place by June 1.

It estimates that increases in power rates above the cap would cost about $10 million a month per cent above the cap, which would be covered by revenue from the Alberta carbon tax.

Provincial electricity rates averaged about 3.9 cents per kilowatt hour between April 2016 and April 2017, but have spiked to as high as 15.3 cents per kilowatt hour in the past six years.

The government says about 60 per cent of consumers pay market rates, while others are on fixed-price contracts that have averaged 6.1 cents over the past year.

Opposition members have criticized the government for what they say is moving too quickly on changing the power market.