Just in time for the summer air conditioning season, the Ontario Energy Board says electricity rates are to rise May 1.

For those on smart meters, the peak price will rise 0.9 cents to 11.7 cents a kilowatt hour, mid-peak will rise 0.8 cents to 10 cents, and off-peak rises 0.3 cents to 6.5 cents.

The energy board said Thursday that translates to an increase of about $3.99, or about 3.3 per cent a month for a typical residential consumer.

Residential customers not on smart meters will see an increase of approximately $5.80, or about 5.1 per cent on a typical monthly bill.

Prices are rising due to changing supply costs as coal generation declines and is replaced with natural gas, nuclear and renewable sources.

The price changes only apply to consumers who buy electricity directly from their local utility.