Several environmental groups are trying a new tactic to stop construction of a new coal-fired generator at Duke Energy's Cliffside plant near Charlotte. They're asking state regulators to deny Duke's rate increase that would help pay for financing the project. WFAE's Lisa Miller has more: Earlier this summer Duke asked regulators to approve a 13 percent rate increase for its North Carolina customers. Under that scenario, the average household bill would go up $180 a year. The state's utility commission is still mulling the request. Twenty-five environmental and health groups sent state regulators a letter yesterday asking them to say no to Duke. Jim Warren with NC Warn is one of the letter's co-signers. "Duke Energy's customers should not be paying higher electricity prices for power plants that are simply not needed," says Warren. The letter says Duke's own data show no new power plants are needed if customers make modest efforts to conserve energy. But Duke Energy says that's not the case. Spokeswoman Paige Sheehan points out that only 20 percent of the increase would help pay for financing Cliffside's expansion. She says the project is almost half-way finished and the rate increase would have no bearing on whether it's completed. "The only role Cliffside has in the rate case is that we have the opportunity to lower the cost of the project by collecting some of the money as we go," says Sheehan. State regulators will begin holding public hearings on Duke's rate increase next week. Duke wants the new rate to go into effect in January.