Water heater timers can save you money on energy costs by shutting the water heater off at certain times and not keeping the water constantly hot.
Water heaters are huge consumers of electricity so if you don't use much hot water there's no reason to keep the water cycling on an off heating unused hot water and wasting electricity and money.
Another option is to change your water heater out for a tankless water heater. A tankless water heater only heats water up when you are using it.