How are peak hours decided?

Peak hours are often (but not always) aligned with those times when most people get off work, return home, and access the grid by cooking, doing laundry, washing dishes etc. Other potential peak times include periods of extreme weather (particularly extreme heat), or during unexpected drops in generation due to natural disasters, fire, or equipment failures. If demand passes certain critical thresholds then peaks can occur and response measures may be implemented as a result.