Complex sentence: In recent years REP has focused heavily on energy and climate issues, advocating for the United States to wean itself off its heavy dependence on oil and other fossil fuels through greater efficiency, and more use of renewable and nuclear energy.
Split into simpler sentences: In recent years, REP has focused heavily on energy and climate issues. REP advocates for reduced U.S. dependence on oil and other fossil fuels through more energy efficiency, and more use of renewable and nuclear energy.