Nova Scotia's Utility and Review Board will decide later this year if ratepayers are entitled to a small refund as a result of a fuel audit on the power company.
Any rebate would work out to only a dollar a month for most homeowners, but Nova Scotia Power disputes it paid too much for coal burned at the Lingan power plant.
The cross-examination of Nova Scotia's Power's fuel experts wrapped up on Friday.
The Review Board's lawyer, Bruce Outhouse, zeroed in on why the Lingan generating station wasn't producing as much electricity during the peak winter months of 2010.
Outhouse said a decision to buy Appalachian coal fixed the problem.
"Why does it say here in this statement that you presented to Liberty explaining the situation that in February and onwards the arrival of these coals have eliminated opacity issues at Lingan?"
Opacity refers to emissions or pollution.
The audit said the utility waited too long to switch to a coal that improved performance at Lingan by 90 percent the next winter.
John Hawkins, Nova Scotia Powers' director of fuel risk management, disagrees.
He blames wet coal for the problem.
"It effectively disappeared for the remainder of the month of January and our explanation for that is that we had experienced significant rainfalls, there's a full page we devoted to the subject of wet fuel being the primary cause," Hawkins said.
The audit blames underperformance at Lingan for a $3.6-million cost to buy replacement energy.
The board must decide if that problem was due to the type of coal or the weather.