Road Map
Margin is the amount of energy from available resources that is above the expected demand in any given hour. Margin is used to understand where there might be a risk of not serving demand when requested. This is called "possible loss of load." Note that margins can also be calculated after an area imports energy from other areas. At WECC, we study the margins before transfers to understand the risk each area would have if the transmission capability disappeared. We then study risks after imports to determine whether the risks can be mitigated using outside help.
Margins can be shown for different periods by calculating a weighted average over time. The weighting used is the expected demand for that hour. This then gives information on the overall annual and monthly weighted average margins in an area.