That is only true if your electric company is actually charging different rates at different hours. Some have that as an optional billing plan. You'll have to look up your EC plans and/or call to switch plans. If they are then set your timers around the peak hours.

Here's a tip, when calculating your usage be sure to put the decimal point in the right place. Meaning, if they are charging you for fractions of a cent, like 9.95 cents per KWH, it would be .0995. Don't put in your calculator 9.95 or you may have a heart attack from what your bill would look like.