At stake with SB 309 is the financial incentive that helps offset the considerable installation costs of solar panels, wind turbines and other equipment for small producers, through a process called net metering. The incentive allowed them to sell any surplus power back to the utility companies at retail rates, currently around 11 cents a kilowatt hour. The bill would eventually lower the credit for the surplus to the wholesale rate, currently about of 3.5 cents a kilowatt hour. Pushing for the change is a coalition of the state's largest utility companies — Duke Energy, Vectren and Indianapolis Power and Light, among them — under the umbrella of the Indiana Energy Association. They say the cost of solar panels has dropped dramatically in recent years and, as the number of solar and wind users grows, the higher retail rate becomes a problem. "When utilities pay retail price for energy, that cost gets paid for by other customers," said Mark Maassel, the energy association's president.