Mississippi Power reported Wednesday the under-construction Kemper energy plant will cost $20 million more.
The company still expects it to be operating on lignite coal by the third quarter of this year.
The monthly report to the state Public Service Commission and the U.S. Securities and Exchange Commission covers costs through April. The total cost now stands at $6.7 billion.
Company spokesman Jeff Shepard said $19 million of the additional cost is subject to the cost cap and will be covered by Mississippi Power and not its rate payers. This includes startup costs such as staffing, training and repairs to the refractory in the gasifier, he said.
The additional $1 million is for financing costs eligible to be recovered from rate payers, subject to the approval of the PSC.
The plant is operating on natural gas, he said, while testing is going on for other systems, which will run on lignite.
"The next major milestone is feeding lignite into the gasifiers," he said.
That is scheduled for summer.