spud1957 wrote:
I had an extension cord that had a slight crack in the insulation and was laying in the damp grass. It caused a partial ground which resulted in a pretty high power bill.
Unplugged the cord, problem gone.
Not saying that is the cord but you may have a partial ground somewhere.
My brother once had a heat tape that did the same thing. Are you sure the heat tape is not shorted out???
This was decades ago and the insurance company took pity on him and paid part of the bill since the heat tape was at fault. I doubt they would do anything like that now.