A metric focuses on robustness and the ability to withstand events.
Last Updated: June 20, 2025
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This metric focuses on robustness and the ability to withstand events. It is designed to capture the total number of gray sky days (GSD) in a calendar year with no more than the threshold value of customer interruptions. The metric is measured in a percentage of GSDs that does not exceed the threshold value. The threshold value varies by utility size and is defined as the percentage of customer interruptions over the total customer base (e.g., 0.375% of the total number of customers). GSD excludes any calendar day with at least one reportable storm-related outage.