Steep declines in solar PV costs in recent years call into question the need for continued subsidies. We leverage administrative data encompassing the near-universe of domestic PV installations in the UK to assess a zero-interest loan scheme for PV in Scotland. Using a matching with difference-in-differences strategy that exploits the decentralized nature of energy policy in the UK, we show that the loan scheme increased adoptions across all wealth deciles, but especially in the least wealthy localities. Loans are a relatively cost-effective approach to accelerate household PV adoption even in when solar potential is relatively low and to promote equitable access to renewable energy.