On a new well insulated tank, how much do you think you're gonna save with a timer? You won't save anything until the water cools down below the point that it would have come on. And my bet is by that time, the timer will be about ready to turn it back on anyway. The bottom line is that especially with an electric tank, which is completely insulated, the water cools so slowly when it's not being used that it isn't going to make a difference big enough to make the installation of a timer worthwhile. And if you have to pay an electrician to do the install, I'd bet you come out a big loser.
I think the OP already has a timer.
The function of the timer is to limit the time that water is heated to nighttime hours.
As an example lets say he and the Mrs. take showers in the morning (day rates) the timer prevents the tank from heating the cold water in the bottom of the tank. When they get home from work, hot water used is still reserve until the rates change and now the water heats.
Without the timer the hot water consumed in the morning is heated with day rates at probably three times the price. With a 140 gallon capacity and two people living there you should never have to pay day rates for hot water.