A council-owned energy company in Bristol has had £12m wiped off its value despite £27m of public investment, the BBC understands.
The details have emerged from a new business plan for Bristol Energy debated at a council meeting.
The BBC has also learned the council has set a £31.3m limit on its investment.
A spokesman for Bristol Energy Ltd said: "We are on track to start paying back to Bristol City Council by 2021."
Bristol City Council has said it remains committed to the energy firm.
Cabinet member for finance, Craig Cheney, said: "It's achieved higher customer numbers than expected, we've invested less than what we had thought we needed to.
"The gross margin is broadly in line with what we have anticipated so we remain fully committed to the energy company and its future."
The firm's value has been reduced by £12m in its annual accounts, by what is termed as an impairment charge. This is used to ensure a company's value is not being artificially inflated or overestimated.
Bristol Energy has 76,000 customers.
In April, the city council dropped its energy contract with the company after it was "undercut" by British Gas.
The firm has also been criticised by rival energy company owner Dale Vince.
He said: "The money that the council has spent on the company has been used to subsidise the bills of all of its customers, of whom only 20% live in Bristol - that's bonkers.
"It doesn't make sense to me, it seems to be a terrible waste of public money at a time when councils really don't have any to spare."
When the council set up the firm in 2016 it predicted a 12% profit by 2021 and 35% profit by 2026. These figures have since been revised.