By the time somebody reaches for the pry bar, the argument about watts is already over. The door is frozen along its full perimeter, the ice is thickest at the bottom corner, and the morning shift is losing production by the minute. Cold storage door heating cables exist so this scene never happens: small circuits that hold frame, threshold and drains just above freezing so the seal never bonds to the opening. Skip them, undersize them, or control them badly, and the doorway ices up on its own schedule.
We build cold room doors in our factory family, insulated leaves with anti-icing capability, and every door ships with its factory inspection report and installation documents. The heating cable is the smallest electrical part on the opening, and it is the part most often left to be figured out later. Three decisions decide whether it works: how many watts, where the cable runs, and what switches it.