This document summarizes models for optimal design of capacity and electricity markets. It discusses determining the optimal capacity structure under centralized planning as an optimization problem. It provides two algorithms for determining the optimal capacity structure while accounting for fixed and variable costs. One algorithm applies when there are several capacity types and capacity constraints are not binding, and the other applies when electricity is produced by standard small generators with the same capacity and different costs. It also examines Nash equilibria for two market architectures and compares equilibrium outcomes to the optimal capacity structure. Finally, it provides an auction design that can select the optimal capacity structure without requiring additional information from producers beyond their own production costs.