I'll give you an example:
Based on one use per day. Your water heater, each time you use it, takes 1 hour and uses 1000 W. If you only turn it on when you use it every day, then you use 1000 W per day.
But again, on the basis of one use per day. Your water heater spends 1 hour per use and consumes 1000 W. Standby for 23 hours consumes 30 W per hour, so the amount of electricity you use per day is 1000 W + 23*30 W = 1690 W.
1690 is more than 1000.
Which one of these do you think is more energy efficient?
(Simply taught as an elementary school student)...