North Carolina residents may see a bump in their electricity bills this spring.

Duke Energy announced today that it reached a preliminary agreement with North Carolina Public Utility Commission staff on an approximately $310 million increase in the customer base rates, about a 7.2% increase. If approved by the North Carolina PUC, the rate increase–based on 10.5% return on equity (ROE) and 53% equity component of capital structure–will take effect February 2012.

“This proposed agreement strikes a balance between today’s challenging economic times and the need to recover the investments made in the electric system to ensure reliability, affordable and clean energy for the Carolinas today and for tomorrow,” said Duke Energy North Carolina President Brett Carter.

As part of an effort to account for the state’s poorest residents, Duke said it would also donate $11 million of shareholder money to its Share the Warmth North Carolina program, a charity that helps low-income residents pay energy bills.

“We believe the additional contribution to Share the Warmth helps address the concerns we’re hearing from customers,” Carter said.

Duke has been investing in various upgrades to its transmission lines and power supply in recent months across its various service regions.

In mid-September Duke American Transmission Company (DATC)–a joint venture between Duke Energy and American Transmission Company–announced it would be building $4 billion worth of new transmission lines in seven distinct projects across Iowa, Wisconsin, Illinois, Indiana and Ohio. The projects, each spanning anywhere from 65 to 696 miles, would be a combination of both 345-kilovolt lines and 500-kilovolt high-voltage direct-current lines.

“We’ve taken a methodical approach to address specific regional transmission needs by building upon work already done and developing innovative solutions in the areas where they are most needed,” said Duke Energy Commercial Business SVP Phillip Grigsby in a statement at the time.

In September, Duke announced the construction of its second wind farm in Pennsylvania, the 69 MW Laurel Hill Windpower Project.

Duke has also deployed pilot smart grid programs in the Carolinas, with about 16,000 meters of smart grid in North Carolina and about 2,000 in South Carolina.

In August, Manager of Technology Development David Masters outlined the company’s smart grid vision and said the company hopes to see the electric grid modernized, and transformed, in the coming decades.

“It’s a very monumental task and what we’ve typically seen is that it’s very hard to get people to understand it because its very broad,” Masters said. “It touches on all aspects of delivering electricity.”

Masters added: the future of smart grid may bring technologies “we haven’t even dreamed of yet.”