Big industrial energy users say the price of electricity has risen sharply in the past month or so, for no apparent reason.
Official figures show wholesale prices are 50% higher than at the same time last year, despite few signs of a looming winter problem.
Major Electricity Users' Group chairman Terrence Currie says lake storage levels are actually average for this time of the year, so he's at loss to explain why prices are so high.
"There's a mismatch between the current lake levels and the wholesale spot prices. We're really seeing prices which indicate that we're in danger of running out of water."
Mr Currie says there is something awry with the current market and he wants regulatory bodies to investigate.
