Cost estimates for Mississippi Power Co.'s mammoth Kemper County plant have risen again.

The company says it now expects the plant to cost $2.88 billion. That's the ceiling of what the Mississippi Public Service Commission has said it might allow the unit of Atlanta-based Southern Co. to charge to customers.

Independent monitors hired by the PSC have also again raised their projected price for the plant, which would mine a soft form of coal called lignite, convert it to a gas and burn it to generate power. The monitors say the plant will now cost $2.82 billion, says Northern District Public Service Commissioner Brandon Presley.

Mississippi Power originally said it thought the plant would cost $2.4 billion, but persuaded the PSC to give it a 20 percent margin of error.