(e) The commission shall, by not later than December 31, 2020, ensure that all eligible low-income electricity and gas customers are given the opportunity to participate in low-income energy efficiency programs, including customers occupying apartments or similar multiunit residential structures. The commission and electrical corporations and gas corporations shall make all reasonable efforts to coordinate ratepayer-funded programs with other energy conservation and efficiency programs and to obtain additional federal funding to support actions undertaken pursuant to this subdivision. These programs shall be designed to provide long-term reductions in energy consumption at the dwelling unit based on an audit or assessment of the dwelling unit, and may include improved insulation, energy efficient appliances, measures that utilize solar energy, and other improvements to the physical structure.