Energy systems planning models are specifically developed for effective planning of energy activities in a regional, national, or global context. However, the planning process is fraught with uncertainties that may affect the effectiveness of the planning. In this study, an interval-parameter linear programming approach is introduced to develop an interval-parameter energy systems model (IPEM) for supporting effective regional energy systems planning under uncertainty. The developed methodology is then applied to a hypothetical regional energy system. The results strongly suggest that this innovative approach can effectively handle the uncertain information expressed as intervals in the energy planning process and provide more satisfactory solutions for the optimization problem of energy allocation and capacity expansion within a regional jurisdiction. Compared with other energy systems models, this model generates two schemes corresponding to the upper and the lower bounds of system objective, which represent two extreme decisions regarding environmental-economic trade-off. The interval solutions allow for detailed interpretation of the trade-off between environmental pollution risks and economic objectives.