Can an extension cord be used to power an automatic garage door opener that is hung from the rafters?
Extension cords are meant for temporary use.
Sure they “can,” otherwise you probably wouldn’t be asking
However, like Mike said, they are not listed or approved for permanent use. In addition, the manufacturers of the garage door openers consider this an “improper installation” that will void their warranty.
Thank yew, good answer.
Here is the NEC version:
“An extension cord has been used as permanent wiring, which is a fire hazard. Recommend installation of a proper receptacle by a qualified electrician”.