Finance is crucial for the low-carbon energy transition. This research takes the solar PV technology as an example to explore whether having state-owned financial institutions, such as national development banks (NDBs), offers advantages in a country for mobilizing finance. By focusing on three selected country cases (The United States without NDBs, Germany with a big NDBs, and China with huge NDBs), the paper first reviews the evolution of solar PV finance mobilization in the three countries from the 1990s to 2018. It then examines the financial strategies and impacts of NDBs and the alternative approaches that the three countries use to address financial challenges for solar PV deployment at different stages. The paper finds that NDBs' direct financier role in the early deployment stage is most important and irreplaceable. Alternative policies can fulfill most facilitative roles of NDBs in unlocking private finance, except NDBs' learning bank role. NDBs' role in channeling information between governments and markets is also hardly replaceable. The paper provides insights for policymakers and implementers of countries aiming to set up NDBs to scale up low-carbon energy technologies.