Platte River Power Authority - which supplies power to Fort Collins and three other cities - spends about $380,000 annually to fund other companies' renewable energy projects.
But Green-e, the company hired by PRPA to track renewable energy credits, said it can't guarantee PRPA funds are actually going to targeted renewable projects.
Renewable Energy Credits are essentially tradable certificates of proof that one kWh of electricity has been generated by a renewable source.
Green-e, owned by the Center for Resource Solutions, audits the sale of renewable energy credits, ensuring that the value green electricity has on the environment is only purchased once through the sale of credits.
But the company cannot verify money going to the owners of renewable energy projects such as Shell is actually being invested in the energy project and not going into the general fund.
"The scope of our audit is limited to the energy being certified," said Alex Pennock, manager of the Green Energy program. "We don't audit the financial side of things."
Nicholas King, managing member of the G2 Energy LLC that runs the Hidden Hollow landfill project in Idaho, said PRPA is getting what it's paying for.
"At the end of the month we get a report from Idaho Power and that tells us exactly how much power was generated," King said. "All the attributes associated with the production go to that PRPA."
PRPA leaves it up to Green-e to do its own homework.
"All we know is that we have to submit paperwork to Green-e at a certain time of year," said Rae Todd, PRPA spokeswoman.
Green-e does not perform the actual audit, Pennock said, but reviews a paper trail provided by an accountant hired by the power authority or the public utility.
"We're matching that the supply of RECS matches the sale of RECs," Pennock said.
The program, which can cost the utility companies between $1,000 and $12,000 a year, also ensures that new projects are clean, built since 1997, and not built to produce renewable energy mandated by the government.
But the financial side is sticky.
"If they make money beyond what is necessary, they might use it for something else," rather than putting it back into renewable energy, Pennock said. "But I don't know why any company wouldn't use that money for the project."
PRPA buys 17.1 percent of its renewable energy mix from Rock River Wind Farm in Wyoming, a project owned by Shell WindEnergy.
Green-e cannot check the financial records to make sure that money paid to Shell is actually going to pay the additional funds needed to build and power Rock River Wind Farm, Pennock said.
PRPA buys RECS from three wind energy projects and one landfill methane gas project in Idaho, Wyoming and Oklahoma. PRPA will not disclose the amount spent at each project citing a competitive market, Todd said.