Using renewable energy to replace fossil energy sources is a sustainable development trend of each country. Vietnam is a country that is very active in implementing the commitments signed at COP26, so the Government of Vietnam is mobilizing all resources, in which resources from the people are a very important resource. In order to have a basis for making recommendations to develop green energy sources, we carried out this study with the aim of determining the relationship between environmental protection attitude and intention to install rooftop solar power, while also considering its regulatory role in the relationship between installation costs and installation intentions. Using linear regression with the participation of the moderator variable for a dataset of 628 people in the southern region of Vietnam. Research results show that environmental protection attitude is an important factor that increases the intention to install rooftop solar power of people in Vietnam. Although the high cost of installation is a barrier to people's intentions, if people have a good attitude, they will overcome the price barrier and move towards the goal of protecting the environment by rooftop solar installation. To be able to take advantage of the great resources of the people in the use of renewable energy, in addition to raising awareness about environmental protection, local authorities need to pay attention to a number of policies on supporting finance to reduce the burden of rooftop solar installation costs.