Gas hot water heater; hot side water line can use a insulator to help keep hot water line 'hot'. Do this for good housekeeping.

Electric hot water heater; the difference is- no flue. Hot water line could use a thermal inslator; this will help keep hot water 'hot' and not lose heat energy. A thermal blanket can also be used; DO NOT USE A THERMAL BLANKET ON GAS HOT WATER HEATERS.