With electric HWH's the efficiency is always 100%. The power that goes in is converted to heat. The only real differences is in the insulation of the tank to hold the heat. I have found that differences are small, saving a few bucks a year at most. Look at the energy guide label to see what the expected usage cost will be, that should give an indication of the level of insulation. Most new tanks from known brands have gone to a foamed in insulation.
look for Energy Factor on box water heaters are packaged in.
Whirlpool makes a .95 energy factor.
water heater is larger due to higher insulation inside of unit.
additional savings can be added by externally insulating w/h
with w/h blanket.
as water heaters run 24/7 it is an item to spend the extra cost on for
the higher efficiency.
best of luck.
The cure of the part should not be attempted without the cure of the whole. ~Plato
heres what I do, I bought the most efficient one I could 80 gallon, then had NYSEG put in a day/night meter. The WH comes on at 11pm and goes off at 7am it can run anytime durring that time it needs to but it only really comes on like once or twice.
After this time it only has 110 volt going to like warm it ..if needed
Now all the electric I use is at 1/2 price at night. Our monthly bills run around 70.00 this is with elcet range, dryer, waterheater.
My neighbor same size home and same number of people has all the same but a NG waterjeater his bill is about 15.00 a month more !