Maybe my water heater is different than yours but when i first turned it
on I wasnt here much showering 4 times a month or so , but my electric
went up 30$ apx , and droped more than that when i went tankless. But
my figures are not documented as yours.
You did the test for 3 hrs, that was with heated water right. What if
the heater full cycled at 3 hr 10 min. You dont know in your test when
the thermostat will call for heat and what that cycle will consume. Im
wondering if a 3 day test wouldnt be more realistic . Water in a tank
retains some heat for 4-5 days, this I know. I just feel but maybe
wrongly that from my past bills Electrics waste alot more electricity
than your findings indicate