So efficiency drops to 50% by 6 years? You have a link?
This should be easily measured by seeing how much gas or kwh it takes to raise the water temp. 1 BTU per pound of water per degree F and 1 Therm of energy from approx. 100 cubic feet of natural gas or 29 kwh of elec heat.
Because, now the replacement time would also depend on how much you spend per therm of NG or elec., in addition to how much a new heater costs.
Sounds like the strategy behind Cash For Clunkers. What's good for society may not be good for each individual in that society.
Do I have a link? NO, I am THE LINK.
I've installed hundreds of water heaters...how bout you?
I've seen them installed and not touched since the day they was installed, they call when they break, nothing inbetween.
From day one, sediment builds in the bottom of them...even if you drain them once a year, that sediment starts to hard scale inside the tank and will not come out, ever.
Furthermore, calcium deposits/mineral buildup become a common thing inside the water heater.
Do you not comprehend that an energy guide rating only is dictated off a brand new unit?
Realistically speaking, if you did install water heaters on a regular basis, you would get the famous statements after an old one has been replaced, "We can't believe how much hot water we have now, and how much faster it recovers."
That's the efficiency as stated on the yellow tag, years from now you can erase those numbers because it grows progressively larger.
You are not making accurate comparables to anything, and as jimbo stated precisely, you're not statistically significant.
Your numbers are fictitious and do not represent anything because there are far too many variables that determine the longevity of a water heater.
Believing a water heater lasting 20 years thinking it is efficient is ignorance. Go to a junk yard and cut an old one open, then tell me where the capacity went along with the ability to transfer heat through solid calcium deposits at the bottom of the tank.
Posting resource links from l0wes? Are you kidding me?