Louisville Metro Government has issued a challenge to the owners of the city’s commercial buildings: get Energy Star certified. Mayor Greg Fischer says he wants at least 25 buildings to receive the designation by the end of the year.Louisville’s sustainability plansets a goal of decreasing the city’s per capita energy use 25 percent by 2025. Encouraging commercial building owners to invest in energy-saving systems is part of that, and the federal government’s Energy Star programawards certifications to the buildings that reduce their energy use by a certain amount.In 2009, Louisville made the Energy Star list of the top 25 cities in the country, based on the number of Energy Star certified buildings. But the city hasn’t been back on the list since. Sustainability Director Maria Koetter says the challenge will hopefully help Louisville regain its position in the next five years.“We really want to kind of amp it up again and get back on that list,” she said. “It is a big deal for the city, because it shows that we’re taking seriously energy efficiency and energy conservation, which goes to the overall goal of reducing our carbon footprint.”Koetter says the city plans to encourage buildings to meet the challenge by participating too; Metro Government will pursue Energy Star certification for three to five city-owned buildings. Koetter says the investments that are required to achieve certification will be more than paid back with energy savings.