A Rolling Brownout is a temporary, rotating reduction in electrical voltage or load across different sections of the power grid to prevent complete system failure during peak demand periods. Utilities implement rolling brownouts when generation capacity falls short of demand, affecting multiple buildings in geographic sequence. These events reduce electricity supply to specific regions for predetermined periods, typically 1-3 hours.
Technical Details
Rolling brownouts differ from blackouts because power is not completely cut off, but voltage is reduced by 5-10%, causing equipment to operate less efficiently. HVAC systems experience reduced cooling or heating capacity during brownout periods. Buildings in the affected zone experience performance degradation lasting the duration of the rolling cycle. Utilities typically issue advance notice of 30 minutes to 2 hours, allowing facilities to prepare. Industrial and commercial customers often receive priority status to avoid inclusion in rotation schedules.
Impact on HVAC Operations
Rolling brownouts typically cause 10-20% reduction in cooling or heating output. Modern HVAC systems with backup power or sophisticated controls can maintain basic comfort. Facilities with critical operations often install emergency generators or battery storage systems to ride through brownout periods. Participation in demand response programs can help facilities avoid rolling brownout impact.