As these models are based on projected unit cost per cost category, their respective projected cost risk and pair-wise projected covariances of cost categories among generating technologies these models can only be used for short- to medium-term, forward-looking analysis. Given their probabilistic nature, they can be used for short-term or (at most) medium-term, forward-looking analysis only. They use historical information in a semi-heuristic way to generate probabilities and tolerance margins of power systems.