Despite years of ongoing claims that they are improving their customer service, St. Petersburg-based Duke Energy Florida and Tampa-based Tampa Electric still lag behind major Southern electric companies in providing satisfactory services to their residential customers.According to the J.D. Power 2016 "electric utility residential customer satisfaction study," Duke Energy Florida not only ranked lowest among large Florida power companies but also trailed all of its sister subsidiaries that also bear Duke names. Each Duke utility ranked below the Southern average for customer satisfaction.Duke Energy Florida spokeswoman Suzanne Grant defended the utility's service performance. "Contrary to your report, we are fulfilling our promise to improve," she said in an email. "While we aren't where we want to be" on the survey, "Duke Energy Florida is making significant strides in our customer satisfaction."Grant said Duke Energy Florida had the "greatest improvement of any utility in Florida and third-greatest in the nation" — a gain of 32 points. "We will continue to push to improve so we are exceeding customer expectations."Those gains, however, have not been enough for Duke Energy Florida to climb out of last place for regional satisfaction. Tampa Electric sub-par ranking — still 12 points higher than Duke Energy Florida — comes as the Tampa utility was absorbed this month by Canada-based power company Emera Inc.Florida Power & Light, which serves southern and eastern Florida and as far north as Manatee County on the state's west coast, ranked tops in the South and second nationwide in the study.Nationally, J.D. Power notes, customer-reported monthly electric bills have fallen to their lowest levels in 10 years and overall satisfaction is on the rise. But electric utility providers continue to struggle to match other industries in customer satisfaction, the study found.The rankings are based on power quality and reliability, price, billing and payment, corporate citizenship, communications and customer service.