I can pick up a Rennai brand, I think it will provide hot water to 4 showers simultaneously for around $400. I have and easy run (electrical) to my fuse panel, which I could run the electrical and then have the installer finish the work.
Imola, I have just replaced a gas-fired tank-type hot water heater with a whole house electric HWOD model. In the end, including the cost of the HWOD unit (about $550) I spent about $2,500, and that was with me pulling the 6-3 w/ground wires that the two 60-amp breakers required. That $2,500 included a changeover from 100 amp overhead service to 200 amp underground service, $800 of that $2,500 was for labor for the ditching and connecting the underground wires to the new meter box and the new electrical panel on the house's porch, the rest was for new service panels for the house and the detatched two-car garage, which had not had electricity for at least the past 40 years, probably more. The wire was almost free, 150' of 4/0 AL wire for only $75 (the cost differential between what it would have cost to provide me with 150' of overhead AL wire and the larger wire needed for the underground service).
Now, having said that, I think it might be easier for you. You are replacing an existing electrical hot water heater, so you already have what, a 30 amp/240V circuit going to the location? Chances are you might be able to get a 2 chamber HWOD unit that might require two 30 amp/240V circuits. In that case, you could get by with the addition of just one more 30 amp circuit to you existing service panel, as long as your calculations of your usage patterns reveals that you won't be taxing your current service beyond it's limits.
OK, you say you want to use a heater that takes two 40 amp circuits, but you also say you have easy access for running the wires, if so I suspect you could easily run yourself two 8 gauge wires, which I understand will carry 40 amp loads......the hardest part of replacing my old tank-type heater was changing over from natural gas to electrical, you may already have the infrastructure to power one of the mid-size units, but it will depend on the nature of the use you anticipate. For me it was easy, I spend only about 60 days per year at the vacation house, and when I shower I can arrange for everything else in the house to be powered down if need be (however, some of my motivation for switching from 100 amp service to 200 amp service was to avoid just that sort of necessity).
I mention this to illustrate that the plumbing part of installing the HWOD unit was the least of the problems, I just hung the HWOD unit near where the old gas-fired water heater stood and hooked the HWOD unit to the current cold water supply and hot water out pipes with 3/4" X 3/4" flexible copper supply lines and it was a done deal--no leaks, no worries, no need for a plumber at all.......
Having made the switch from natural gas to electrical did, however, allow me to disconnect from the natural gas company's distribution network. I may spend another $20 or so per month on electricity, but I did manage to ditch a minimum $40/month natural gas bill. And, to make it even better, the local poco will now offer me a reduction of about 40% on my electrical service b/c I am now "...all electric".
It will take a long time before I could ever recoup the $2,500, that's true, if I could ever do so at all, but your case might not represent as significant a retrofit as mine did, at least get some people to come to your house and give you some estimates or advice. This might be a DIY project, if mine was, this most assuredly is!!
Dugly
