So lets say we are going to need a 220volt hook up... okay so thats a little downside for exsisting residential... but chances are people will not get a new water heater until the old one poots out.
new residential not a problem as long as life cost justifies pulling a third 220 volt the other two being dryer and stove.
commercial well they have enough money and if it meets the requirements of their needs they will do it if the cost per use is less..
what is the efficiency of the 220 unit u quoted from home depot? i would say we have a chance of reaching close to 100% efficiency if our magnetrons need to be water cooled which they do the only heat will be lost will be cold pipes to source and from convection from the box if it is not well insulated.
if you still believe in physics you should youtube perendev magnectic motor where a simple reaction gets the motor started and the opposite polled magnets keep the reaction going!
Follow him to the LIGHT! If you want HOT showers...