Most growers skim past a number printed on their utility bill: the rotating outage group, or block, that shows where their site sits in the queue when the grid runs short of power. Ian Knisely, an energy analyst at Energy Bridge Advisors, argues that greenhouse operators should read that line as a prompt to write their own plan rather than wait for the utility to act.
The queue exists whether or not it appears on paper. Federal reliability standards, specifically NERC's EOP-011, require grid operators nationwide to keep emergency plans for cutting load, Knisely notes, but California is unusual in printing the assigned group directly on the bill. When such a plan is implemented, power is shut off systematically, often with only minutes of warning. Hospitals and other critical facilities are protected where possible; nearly everyone else, greenhouses included, is exposed.
Rolling outages have hit several regions in recent years, during heat waves as well as winter storms. For a greenhouse, that means fans, pumps, irrigation, heating and environmental controls going dark at the worst possible moment.
Outage or curtailment: the difference is control
In an outage, everything stops at once. In a planned curtailment, the grower decides in advance which loads drop, by how much, and which stay on to protect the crop. Knisely describes a curtailment plan as a written playbook for the hours when the grid is stressed, and reduces most of them to four steps.
- Inventory the loads. List the major equipment and roughly how much power each piece draws: supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and any cold storage.
- Sort what can go. Some loads can drop entirely for a few hours without harm to the crop. Some can be trimmed, such as dimming lights, staggering fans or moving a setpoint a few degrees. Others must stay on regardless, including controls, alarms and whatever keeps the most sensitive crop alive. The sorting depends on the crop and its stage, so it can change through the season.
- Set the trigger. An outage order may arrive with minutes of notice, but heat waves and cold snaps are forecast days ahead and grid operators usually issue public alerts before an emergency. Growers with a plan treat those signals as their cue: in summer, pre-cooling in the morning, irrigating early and closing shade curtains before the afternoon peak; in winter, heating ahead of the cold peak, closing thermal curtains early and making sure backup heat is fueled and tested.
- Assign roles. Decide who receives the alert, who makes the decision and who carries it out. If the environmental controller can run the sequence automatically, program it and test it. A plan that hinges on one person answering a phone at 4 p.m. on a Saturday is not a plan.
The number the grid will pay for
Once those steps are done, a grower should know how many kilowatts can be surrendered, for how long, and at what cost to the crop. That figure is what the grid is willing to pay for. Before ordering outages, utilities and grid operators pay customers who agree in advance to cut load, a market known as demand response, because a megawatt that disappears on request is cheaper than one bought at emergency prices. The market operates in most of the country, largely so that the outage plan never has to be used.
Knisely's advice to growers is to ask their utility where their site falls in its plan, then start building their own. He is an energy analyst at Energy Bridge Advisors, which works with controlled environment agriculture operators to cut utility costs and turn energy flexibility into revenue, and previously worked at BrightFarms and Curaleaf.