Electric and gas utilities in the U.S. invest billions of dollars annually to help their customers become more energy efficient, often by making repairs and improvements to customers’ homes and buildings. These investments are smart – they improve lives by reducing energy expenses, create healthier, more comfortable houses and offices, and improve community building stock. Most housing programs and mortgage lenders typically define a multifamily building as a building with five or more dwelling units.7 Buildings with four or fewer units, duplexes, townhomes (2 or more units connected by party walls) are typically categorized as single-family attached housing. Most construction in recent years is buildings with five or more units. About one in four dwelling units (25 percent) in the US are in multifamily buildings. Multifamily buildings are heavily dominated by renters (87 percent). Single-family housing, in contrast, is more than 80 percent owner-occupied. About two-thirds of multifamily units are in buildings of 20 units or fewer. Many housing experts predict long-term growth for the multifamily housing market. This is based on fundamental demographic trends, including a shift in demand away from suburban and exurban locations and toward urban dwellings.