On the day Mississippi Power Co. was scheduled to start commercial operation of its Kemper County energy facility, another month’s delay was announced.

The utility, a unit of Atlanta-based Southern Co., revealed the setback in a U.S. Securities and Exchange Commission filing Tuesday, the latest in a series of missed projected deadlines.

The plant, which is running on natural gas, was supposed to go into full operation running on synthesis gas, also known as syngas, by May 2014. It is now scheduled for completion by Feb. 28.

In Tuesday’s filing, Mississippi Power says it has integrated the operation of both of the plant’s gasifiers and was able to produce electricity from syngas in both its combustion turbines on Jan. 29.

However, the utility says the plant must undergo an outage of about one week to repair and make modifications “to further improve the plant’s ability to achieve sustained operations sufficient to support placing the plant in service for customers.”

As in previous filings, Mississippi Power estimates that missing its latest deadline would cost about $25 million to $35 million per month. This latest delay pushes the plant’s price tag to almost $7.1 billion. Additional costs may also be required if any further equipment or design issues emerge, the utility says.

As for what the public pays, there is a $2.88 billion cap on what Mississippi Power rate payers can pay for the plant. Any increase beyond that depends on Mississippi Public Service Commission approval.