TORONTO -- Electricity rates are going up again in Ontario, just in time for the longer summer days.

Time-of-use electricity prices will jump half-a-cent to 18 cents a kilowatt hour for peak periods, from 11 a.m. to 5 p.m. weekdays, starting May 1.

The rates are up slightly less for mid-peak periods -- between 7 and 11 a.m. and 5 to 7 p.m. -- at 13.2 cents a kwh.

Off peak rates -- in effect from 7 p.m. to 7 a.m. and all day weekends and holidays -- are also going up to 8.7 cents a kwh.

The Ontario Energy Board estimates the changes will add about $3.13 a month to the electricity line on the average monthly hydro bill for a household using 750 kwh a month.

The board sets rates every six months, and adjusts the hours for peak and off-peak periods, with changes every May 1 and Oct. 1.