Greenhouse growers may check utility bills for costs, but in California the bill also identifies a rotating outage group or block, showing where a site stands if the grid runs short. Federal reliability standards, including NERC's EOP-011, require grid operators nationwide to keep emergency plans for cutting load. California is unusual in printing that information directly on bills.
Utilities across the country keep plans for systematically shutting off power when supply cannot meet demand, often with only minutes of warning. Hospitals and other critical facilities are protected where possible; most other customers, including greenhouses, are at risk. Rolling outages have affected several regions during heat waves and winter storms, potentially stopping fans, pumps, irrigation, heating and controls at a critical time.
Outage versus curtailment
An outage stops everything at once. In a planned curtailment, the grower decides in advance which loads to drop, how much to reduce and which must remain on to protect the crop. A curtailment plan is a written playbook for stressed grid hours, built around four steps.
- Inventory loads. List major equipment and estimate power draw for lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and cold storage.
- Sort equipment. Identify loads that can be cut for a few hours without crop harm, loads that can be reduced by dimming lights, staggering fans or adjusting a setpoint, and loads that must stay on, such as controls, alarms and systems protecting sensitive crops. The sorting can change with crop and growth stage.
- Use forecasts as triggers. Outage orders may arrive minutes ahead, but heat waves and cold snaps are forecast days ahead and grid operators issue alerts. Summer preparation includes pre-cooling, early irrigation and closing shade curtains before the afternoon peak; winter preparation includes heating ahead of the cold peak, closing thermal curtains early and making sure backup heat is fueled and tested.
- Assign roles. Decide who receives alerts, who makes decisions and who carries them out. If an environmental controller can run the sequence automatically, program and test it.
After those steps, a grower should know how many kilowatts can be given up, for how long and at what cost to the crop. Utilities and grid operators may pay customers that agree in advance to cut load through demand response, a market that exists in most of the country and is intended largely to avoid emergency outages. Growers should ask their utility where a site falls in its plan, then write their own.