Constellation Energy shares tumble

Constellation Energy's shares fell $2.39, or 9.5 percent, to $22.86 in afternoon trading. The stock has ranged from $13 to $107.97 over the past year.

Berkshire unit MidAmerican Energy announced Sept. 18 that it would buy Constellation Energy for $4.7 billion, or $26.50 per share, and give it an immediate $1 billion infusion. The deal came after Constellation Energy's shares declined sharply and liquidity concerns had analysts worried that the company would go out of business.

The companies released a statement Monday afternoon saying the merger is proceeding as planned.

Baltimore-based Constellation Energy, the nation's largest power wholesaler, supplies electricity to large commercial and industrial customers. It also manages fuels and energy services on behalf of energy intensive industries and utilities and owns 83 generating units in the U.S. It is the parent of Baltimore Gas and Electric Co.

MidAmerican Energy, based in Des Moines, Iowa, bills itself as a global leader in energy production from sources including natural gas, hydroelectric, nuclear, coal, geothermal and wind. The company, with more than $12 billion in annual revenue, distributes energy in the U.S. and U.K. consumer markets, with approximately 6.7 million electricity and gas customers. Its subsidiaries include California utility PacifiCorp.