dallasiteinsa02 said:
Haven't looked into it in a while, but the tankless electrics usually suck.
Hmm...Endless hot water and nearly 95% efficiency (won't happen with gas tankless) sucks? If anyone has any questions, I have 3 in my home and have owned them since 2000. It was designed for them so they are not retrofits. They have each been replaced once. Happy to answer any questions.
One thing you will have to address, OP, is that my smallest unit uses dual 40A breakers to run. Most people do not have the electrical capacity or willingness to bring their electric up to snuff for this kind of load.
It is completely dependent on the unit you buy. Some are Dual 50A, some are single 50A, some are dual 40A. The electrical is a problem for most people. You need the proper wire, breakers, and space (physical and electrical) to have it done right.
Main disadvantages for retrofit are costs associated with the units, plumbing and electrical upgrades required. My system is setup with zoned systems in case one fails. There is always hot water in a shower somewhere. For a whole house unit like you will require, the electrical will be hefty as will the ass pain if it fails and you cannot replace it with an identical unit of size, shape, and electrical requirement quickly.