Jadnashua
Retired Defense Industry Engineer xxx
20Kw~68K BTU. An electric water heater is nearly 100% efficient, so each of those watts/BTU go into heating the water.
1 BTU will raise one pound of water one degree F. A gallon of water = 8.3#. If you know the incoming water temp, and the outgoing temp from the WH, you can figure out how many gallons it heated, but some of that would be lost in standby...probably not much more than 5% or so, though, in radiational losses. See how that compares to what you think you are using in hot water during a typical day.
1 BTU will raise one pound of water one degree F. A gallon of water = 8.3#. If you know the incoming water temp, and the outgoing temp from the WH, you can figure out how many gallons it heated, but some of that would be lost in standby...probably not much more than 5% or so, though, in radiational losses. See how that compares to what you think you are using in hot water during a typical day.