An optimal operating configuration for a power system may be derived from a continuous-time model of generation and ramping constraints of power generation units available within the power system. The optimal operating configuration may be leveraged to calculate a valuation metric for power generated by the power generating units. The valuation metric may include costs incurred by the power generating units due to ramping events. In addition, incremental generation and ramping cost metrics may be used to identify power generation units to use in responding to short-term load variations. Power generating units may be selected based, at least in part, on the incremental ramping costs of the power generating units.