Due to the increasing energy consumption of the world, new alternative energy sources are needed. The alternative energy resources can be classified into three categories such as fossil fuels energy resources, renewable energy resources, and nuclear energy resources. Solar energy is a very commonly used renewable energy resource for generating electricity and heating water. In this paper, establishing a solar energy system is handled as an investment analysis problem whose parameters are defined under uncertainty. Therefore, neutrosophic sets as a mean of dealing with uncertainty have been preferred to capture this vagueness and impreciseness. Neutrosophic sets are one of the extensions of intuitionistic fuzzy sets, which use an indeterminacy function unlike the other extensions of fuzzy sets. This paper proposes a new neutrosophic investment analysis method by using interval-valued parameters to evaluate solar energy systems. In the application section, three different types of solar energy systems are evaluated by the proposed method. It is observed that the proposed method presents big flexibility to experts and it gives effective and efficient results.