Great Plains Energy announced Tuesday it plans to acquire Westar Energy.

Great Plains Energy Incorporated (NYSE: GXP), the parent company of KCP&L, and Westar Energy, Inc. (NYSE: WR), Tuesday announced a definitive agreement for Great Plains Energy to acquire Westar in a combined cash and stock transaction with an enterprise value of approximately $12.2 billion, including total equity value of approximately $8.6 billion. Upon closing, Westar will become a wholly owned subsidiary of Great Plains Energy.

Once the transaction is complete, Great Plains Energy will have more than 1.5 million customers in Kansas and Missouri, nearly 13,000 megawatts of generation capacity, almost 10,000 miles of transmission lines and over 51,000 miles of distribution lines. In addition, more than 45 percent of the combined utility’s retail customer demand can be met with emission-free energy.

“Westar and KCP&L are trusted neighbors and have worked together for generations in Kansas. The combination of our two companies is the best fit for meeting our region’s energy needs,” said Terry Bassham, chairman and chief executive officer of Great Plains Energy and KCP&L. “This is an important transaction for Kansas and our entire region. By combining our two companies, we are keeping ownership local and management responsive to regulators, customers and regional needs, while enhancing our ability to build long-term value for shareholders.”