Billionaire Warren Buffett’s energy company may be showing some interest in possibly purchasing Hawaiian Electric Co. if state regulators don't approve NextEra Energy Inc.'s $4.3 billion acquisition of the Honolulu-based utility, Pacific Business News has learned. MidAmerican Energy Services LLC, a Berkshire Hathaway Energy Company, was recently registered as a new business in Hawaii, according to public records. The Des Moines, Iowa-based retail energy services organization has a total of 60,000…