Conventional storage water heater fuel sources include natural gas, propane, fuel oil, and electricity. All conventional water heaters store hot water 24 hours per day in a storage tank, typically ranging in volume from 20 to 120 gallons.
To minimize stand-by losses you should consider water heaters that offer higher levels of tank insulations. Often the lowest-priced storage water heater may be the most expensive to operate and maintain over its lifetime.
There will always be hot water. Endless hot water - for bathing, cooking, dishes, laundry, and all the other countless ways hot water enriches our lives.