This study investigates how changes in energy prices, interest rates, and investment costs impact the Net Present Value (NPV) and Internal Rate of Return (IRR) of three alternative energy projects: a solar PV (photovoltaic) system, a woodchip-fired boiler, and a heat pump system. Rather than comparing these projects directly, the paper aims to illustrate how returns on alternative energy investments have evolved under economic conditions specific to Hungary. The central focus of this study is to highlight the economic rationality of postponement decisions which is one of the most adverse effects of unpredictability, in addition to the numerous inhibiting factors listed in the professional literature. In conclusion, this study highlights the inherent risks in making investment decisions at any single time for projects expected to yield returns over the long term, emphasising the importance of evaluating the main factors that affect potential returns. In all three projects, the application of random shocks shows that the probability of a negative net present value, i.e. non-return on project expenditure, is greater than 55%. Through the case studies presented, the study shows that the state has a role to play in reducing risk by providing investment subsidies, tax incentives, favourable fixed-rate credit schemes and a predictable regulatory environment.