Capacity Market

A capacity market is a market mechanism designed to procure commitments from resources to be available during future periods of system stress or high demand. Instead of paying only for actual energy produced, it pays eligible resources for maintaining dependable capacity that can support reliability when needed.

Capacity markets are typically introduced where policy makers or system operators believe that energy-market revenues alone may not produce enough reliable investment. Their design therefore has major implications for adequacy, technology mix, and the long-term economics of generation and demand-side participation.

Key Aspects of Capacity Markets:

• Availability Rather Than Energy: Capacity payments compensate resources for being available to perform when the system is tight, usually measured in MW of accredited capability. The resource may not run continuously, but it must be ready to contribute under specified reliability conditions.
• Resource-Adequacy Objective: The main purpose is to support long-term adequacy by ensuring enough dependable capacity exists to meet peak demand plus required reliability margin. This is a planning and investment signal rather than only a short-term operating tool.
• Forward Commitment Structure: Many capacity markets procure commitments years in advance so new or existing resources can plan investment and maintenance with greater certainty. This forward horizon strongly influences the type of projects that can participate competitively.
• Design Sensitivity: The effectiveness of a capacity market depends on how reliability value is defined, how penalties and performance obligations work, and how different technologies are accredited. Small design choices can significantly change market outcomes.
• Debate and Tradeoffs: Capacity markets can improve investment visibility, but they can also distort energy-market signals or favor certain resource classes if poorly designed. Their benefits must be weighed against alternatives such as scarcity pricing reform, strategic reserves, or reliability contracts.