The transition to distributed solar power depends not only on panels and inverters but on the software that helps customers size, finance, operate, and optimize their systems. “Solar assistants” — web apps, mobile tools, and embedded device agents that recommend system designs, estimate savings, and manage production — are becoming central to consumers’ decisions. But poorly designed assistants risk misleading customers, creating security vulnerabilities, and locking users into proprietary ecosystems. We need solar assistants that are verifiable, secure, privacy-preserving, and equitable.