I saw it in the 80’s, and can’t remember much about it, except for this:
After killing the protagonist inside their home, the antagonist heads to the bathroom and takes a bath.
Only the protagonist is not really dead! We seem them pushing a toaster from the kitchen, into the living room, and down the hall, finally into the bathtub, killing the murderer, and serving justice through the world’s longest appliance cord.
It was a long, drawn out scene, in which the toaster was slowly pushed through the house. We first saw said toaster as it rounded the couch. Nobody in my group could tell what it was, until someone said, “Is that a toaster?”. Then the toaster was pushed down the hall, etc.
That’s gotta be it. It goes down just as described in the OP, except the toaster is not plugged in in the kitchen; the woman is shown plugging in the toaster just outside the tiny bathroom.