Castleton Baptist Church near Newport found itself charged nearly £44,000 by energy supplier SSE, a significant leap from their usual monthly power bill of under £300.
None of the 80-strong congregation saw the huge gas bill envelope before the huge direct debit was taken because the church has no letterbox to post it.
The revelation came to light a week later when the church treasurer, Nathan Evans, examined the account.
The regular monthly bill for the church building in Marshfield typically ranged from £200 to £300. Mr Evans said that when SSE recalculated the bill in question it should have totalled just £304.
Having acknowledged the mishap, SSE issued a formal apology and provided £500 compesnation as a goodwill gesture, though the church had to wait over five weeks for the funds to be returned.
Treasurer Nathan Evans expressed his initial reaction to the staggering deduction as "total shock and panic."
He told South Wales Argus: "When I saw the money that had been taken my reaction was total shock and panic.
"SSE say they sent an invoice sometime at the end of November 2023 on paper. The church has no letterbox so it never got to me."
Rev De Lima said that the money would have previously have left the church overdrawn but said: "We very fortunately had a substantial legacy left to us by one of our members and that was the only reason we had the money in there.
"Without that for sure the account would have been overdrawn."
A spokesman for SSE Energy Solutions said: "We are sorry for the issues the customer has encountered with their bill.
"This was caused by the incorrect submission of a meter reading by a third-party industry operator, which our internal checks regrettably missed before the customer was billed."