I have bid on about 10 electric tankless installations and all of them have ended up abandoning the project or going with gas. The amount of electricity needed to run one for an average single family dwelling, about 125 amps at 240 volts, is just to much of a burden on a normal 200amp service. The only practical application I have seen of an electric tankless is in an industrial setting with a 600 amp or more main service. Don't you have gas available? Using electricity to make heat only makes sense if you have no other option.

__________________
1984 300TD 1981 240D