To Whom It May Concern,

I have been asked to design an electrical patio heater and I need to verify what is the maximum wattage that I can legally use in the USA. One source told me nothing more than 1500W. Is this true or is it another number?

Thank you for your time.

P.S. If I have the wrong category please let me know.

I am understanding that you are looking for the maximum power that a 120V 15A receptacle can supply?

Simple math is 120V X 15A= 1800W for a non-contiuous load (~20min intervals). For a continuous load (80%)= 1440W.

It's not the load that is the limiting factor, it's the power supply! And remember, receptacles may be shared so the load is also shared. Voltage may also be lower so power supplied is lower. I'd use 105V instead of 120V to be safe.