Outlet is discolored from my Edenpure heater

My Edenpure heater runs 24/7 in the winter months. The outlet is overheating and the outer plastic is dark brown. I moved it to another outlet and I am plugging the Edenpure in directly, no extension cord. So I tried a multi-plug with a circuit breaker and it burned out.This outlet is now burnt looking too. The Edenpure wasn’t running is the only way I discovered it. It probably gave its life protecting my house from a fire. Is there a different outlet I can install that will carry the heavy load of my constantly running heater?