I installed one of these back in July and the customer I did this for was very technical.
He said that in order for his savings to be had,
He has to keep it 12 years in order for it to pay for itself. Roughly $2200.00 installed was the investment.
The warranty is only 10 years on this unit.
He has chronic hard water, and buildup in this tank is guaranteed.
I couldn't even get him to drain the old one initially and I'm curious to know if he'll drain this new one once a year to keep it operating properly.
It is very quiet, no louder than a high efficiency furnace.
I for one understand the condition of a 10 year electric water heater in a hard water region. No way will the efficiency of that heater stay even within the first 6 months of use over 10 years, let alone 12. !!!
Lots of parts to fail, including the electronics to this unit over the life of the unit.
If he calls when it malfunctions, I won't be the one to work on it. It'll be an authorized rep that narrows the playing field and raises the price to the final cost.
Would I as a plumber promote this unit?
Most likely not, knowing that you "have" to maintain this unit...which is draining it once a year, replacing the anode rod every 3 years would be smart, and not having any control over water conditions will affect it.
If this system is used heavily, of course there's a greater chance for repairs in the future...and do you really want to spend $$$ amount of dollars to keep what will be outdated technology when the time comes, and it won't be efficient.
You could get "possibly" better efficiency by replacing a cheaper tank heater every 3 years, knowing it isn't aged and costing you more than the energy guide dictates.
Jury will be out on this...don't think you'll have fistfuls of cash after paying your electric bill each month. Especially when it took a personal loan just to buy it...5 times the price of a regularly priced electric water heater. Yikes.