City of Gillette, WY
This utility did not file a reliability report
City of Gillette is one of only 12 utilities nationally that filed no outage-frequency or outage-length figures in the most recent federal reliability filing. That is a gap in the reporting, not evidence the grid in Wyoming is reliable or unreliable - there is simply nothing filed to measure it against. Check the Wyoming state figure below instead, or ask City of Gillette directly for its own outage history before deciding on a generator. Who owns a utility says a lot about its likely record - see co-ops vs city-owned utilities.
How City of Gillette's record was measured
These figures come from EIA Form 861, the reliability report a municipally-owned utility like City of Gillette files with federal regulators every year - averaged across the whole territory, not any one address or storm. Every other utility in Wyoming is covered too: see Wyoming's full record. Storm days are counted in - here is why.