Water Heaters in Manufactured Homes

I know the breaker size and wattage are different for water heaters in manufactured homes. If they put in a new heater with 4500 watts is that a major issue?

You would need 10 gauge wiring and a 30 Amps. breakers for a 4500 watts WH. Why would it be different for WH in manufactured homes?

The ones I have seen have 20amp double breakers and a 12 awg wire. I guess it should be 3500 watts?

That would be for a 40 gal. 3,000 watts WH.

What would happen if you have a 20amp double with a 12awg wire on a 4500 watt heater? Would it just be less efficient?

You could overload the breakers and wiring. Do the calculations.

Bear in mind that the gauge partially depends on copper vs aluminum, with aluminum you need to go one size AWG down (larger wire).

I was told by an electrician and a plumber that the wattage is not as important as the wire size and breaker. A 240 20 amp breaker with a 12 gauge wire(copper) will not overheat even with a 4500 watt heater. Either the breaker will trip or the heater will just be less efficient than having a 3500watt