those can be issues
That and the fact that most homes built before or w/o THWH do not have circuitry under the sink.....
THWH to replace my standard electric 40 gal. At the faucet in the kitchen it produced 104 F water. At the upstairs MB tub- only 89F. Last one whole day and my wife looked at me a said “ I can take a bath, after you carry 20 gals of boiled water from the kitchen stove top, get started smarty pants”? I returned it the next morning and installed a standard 50 gal version.
I did install a THWH in our motor home to supplement the gas/electric main 6 gal HW heater- when running off of shore power it produces great HW- and since I am paying a flat fee for shore power.... I can also run it off the generator and it only draws 3Kw, so AC works fine too.