The Booth-Baleriaux piecewise-linear method of calculating power system production cost and reliability is extended to include a piecewise-quadratic representation of the equivalent load duration curve. Grid increment size can be chosen without dependence on generator capacities. Twenty or fewer grid increments yield an execution speed and an accuracy that are comparable with the method of cumulants and the mixture of normals approximation. Fifty or more grid increments yield accurate results for expected unserved energy and loss of load probability. The piecewise-quadratic method overcomes limitations inherent in other methods.