Greenhouse growers spend plenty of time planning for weather, pests and markets, but many have no plan for the moment the power goes out. Energy analyst Ian Knisely argues that gap leaves crops exposed whenever a grid operator moves to cut load.
Under federal reliability standards, grid operators across the U.S. must maintain emergency plans for shedding load when supply cannot keep up with demand. Knisely points to NERC's EOP-011 as the requirement behind them. When such a plan is triggered, power is switched off in a systematic sequence, often with only minutes of notice. Hospitals and similar critical facilities are protected where possible; nearly everyone else, greenhouses included, is not.
California is unusual in making the process visible. Utility bills there print a customer's rotating outage group or block, showing the account holder where it stands in the queue. In most other states, Knisely notes, growers still occupy a place in that line whether or not it appears on any bill.
Rolling outages have hit several regions in recent years, during both summer heat waves and winter storms. For a controlled-environment operation, the consequences arrive all at once: fans, pumps, irrigation, heating and environmental controls go dark together.
The difference between an outage and a curtailment
Knisely frames the distinction as a matter of control. In an unplanned outage, everything stops simultaneously. In a planned curtailment, the grower decides in advance which loads to drop, how far to cut them, and what must keep running to protect the crop. A curtailment plan, in his description, is a written playbook for the hours when the grid is under stress, and most such plans come down to four steps.
- Inventory the load. List the major equipment and roughly how much power each item draws — supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and any cold storage.
- Sort by priority. Some loads can be shut off entirely for a few hours without harm. Others can be trimmed by dimming lights, staggering fans or nudging a setpoint a few degrees. Controls, alarms and whatever keeps the most sensitive crop alive must stay on. The sorting depends on the crop and its stage, so it can shift over the season.
- Pick the trigger. An outage order may arrive with minutes of warning, but heat waves and cold snaps are forecast days in advance, and grid operators usually issue public alerts before an emergency. Growers with a plan treat those signals as the starting gun. In summer that means pre-cooling in the morning, irrigating early and closing shade curtains before the afternoon peak; in winter it means heating ahead of the cold peak, closing thermal curtains early and confirming backup heat is fueled and tested.
- Assign roles. Decide who receives the alert, who makes the call and who carries it out. If the environmental controller can run the sequence automatically, program it and test it. A plan that depends on one person answering a phone on a Saturday afternoon is not a plan.
A number the grid will pay for
Once those steps are complete, a grower should know how many kilowatts can be surrendered, for how long, and at what cost to the crop. According to Knisely, that figure is exactly what the grid is willing to pay for. Before ordering outages, utilities and grid operators prefer to pay customers who agree in advance to cut load, because a megawatt that disappears on request is cheaper than one bought at emergency prices. That arrangement is demand response, and it exists in most of the country — largely, he writes, so the outage plan never has to be used.
His advice to growers is direct: ask the utility where the site falls in its plan, then start building a plan of their own.