Under the uncertain and the flexibility required conditions, the conventional capital budgeting techniques are insufficient to decide the most feasible investment due to their static nature. Classical real option valuation techniques have been used for various investment options such as deferment and abandonment. Although these techniques help to evaluate the projects in uncertain environments, they still follow the static, certain Boolean logic assumptions. Therefore, further improvement in the real option valuation has been introduced with the usage of fuzzy logic. Fuzzy logic is applied by binomial and Black-Scholes real option valuation methods up to date, but not with the trinomial lattice. Moreover, Types-1 and 2 fuzzy numbers are used; however, the intuitionistic fuzzy numbers are not analyzed in detail in the real option valuation. In this article, we propose an intuitionistic fuzzy trinomial lattice real option valuation model for a solar energy investment project. While valuing the deferment option, expert opinions, two different volatility methods, and a tailor-made electricity price-forecasting model are used. According to our results, the deferment option is valuable and delaying the start of the project provides a much higher expanded net present value than an immediate start. The contribution of this article is that the uncertainty in the real option valuation is modeled from a broader perspective with intuitionistic fuzzy numbers by taking the hesitancy of the decision-maker and the market into account. Consequently, the proposed method would increase the accuracy of the real option valuation in uncertain environments such as renewable energy sector.