California apartment buildings – and those of other states across the country – could be the future of rooftop solar. This is provided that the tech, policy and biz models line up correctly. Around tech that means having the ability to solve the split-incentive barrier (a lack of alignment between renters and property owners). In policy, at least in CA, the NEM reform will determine much. It also means models that embrace lower-income and disadvantaged residents. The software company Ivy Energy has been working on a solution that can apparently make rooftop solar work for multifamily housing.