harry wrote:
On Apr 12, 2:12�pm, mike wrote:
My electric water heater has a sticker that says it uses
4720 KWH/year.
How is that number calculated?

I assume there's a standard somewhere with assumed temperature
for input water and air ambient and some number of gallons heated.???

I can calculate the energy needed to heat the water I use.
I need a way to estimate the energy radiated from the
tank. �I'm way to lazy to try to measure it.
Thanks, mike

They make an assumptiom about how much water you use.
They make and assumptiom about how cold your water is when it comes
into the house.
They make another assumption about how hot you use your water.
They make yet another about how thermally efficient your water heater
is.

A gallon of water wieghs around 10 pounds.
Every pound of water takes 1BTU to raise it 1deg Fah.
There are 3412 Btu in I Kwh.
There yah go. Doncha wish you was metric like us over here?

There are so many assumptions it's all ******** in fact.

I'm asking what assumptions they make. The rest is just math.