Commercial greenhouses are built to control temperature, moisture, light and irrigation, but those systems depend on continuous electricity. The article by Ian Knisely, an energy analyst at Energy Bridge Advisors, starts with a detail many growers overlook on a California utility bill: the rotating outage group or block. That number indicates where a site stands in line if the grid runs short. Every grower has a place in that line, whether or not it is printed on the bill.
Federal reliability standards—NERC’s EOP-011—require grid operators nationwide to maintain emergency plans for cutting load. California is unusual in printing the information directly on utility bills. When such plans are implemented, power is systematically shut off, often with only minutes of warning. Critical facilities such as hospitals are protected where possible, but almost everyone else, including greenhouses, is at risk. Rolling outages have hit several regions in recent years during heat waves and winter storms. For a greenhouse, that means fans, pumps, irrigation, heating and controls can go dark at the worst possible time.
An outage is not a curtailment plan
The distinction 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 remain on to protect the crop. A curtailment plan is therefore a written playbook for the hours when the grid is stressed. The article outlines four practical steps.
- Inventory the electrical load. List major equipment and roughly how much power each piece draws: supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and any cold storage.
- Sort loads by crop risk. Some loads can be dropped entirely for a few hours without harming the crop. Others can be reduced—by dimming lights, staggering fans or adjusting a setpoint by a few degrees. Controls, alarms and whatever keeps the most sensitive crop alive must stay on. The sorting depends on what is grown and its stage, so it can change through the season.
- Treat forecasts as triggers. 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 act on those signals. In summer, they pre-cool in the morning, irrigate early and close shade curtains before the afternoon peak. In winter, they heat ahead of the cold peak, close thermal curtains early, and make sure backup heat is fueled and tested. The crop enters the critical hours with some margin.
- Assign decisions and automate where possible. Decide who receives the alert, who makes the decision and who carries it out. If the environmental controller can run the sequence automatically, program and test it. A plan that depends on one person answering a phone at 4 p.m. on a Saturday is not a plan.
Once those steps are complete, a grower should know how many kilowatts can be given up, for how long and at what cost to the crop. That figure is the basis for a conversation with the grid. The article’s analysis is operational rather than financial: it does not promise a payment level or prescribe equipment. It argues that the value of a curtailment plan comes from knowing the trade-offs before an emergency rather than discovering them during one.
The practical risk is broader than the loss of a single system. Fans, pumps, irrigation, heating and controls all draw on the same electricity supply, and the article notes that an outage can stop them at the worst possible time. The difference between an outage and a curtailment is the grower’s ability to decide in advance. That makes the plan a crop-protection tool as well as an energy-management tool, and it explains why the sorting step cannot be fixed once and forgotten: a load that can be dropped at one growth stage may need different treatment at another.
Demand response changes the economics
Before ordering outages, utilities and grid operators will pay customers that agree in advance to cut load. The reason is that a megawatt that disappears on request is cheaper than one bought at emergency prices. That market is demand response. It exists in most of the country, largely so the outage plan never has to be used.
The implication for greenhouse operators is twofold. First, a site needs to know where it falls in its utility’s emergency plan. Second, it needs its own plan for which loads can be shed, which can be reduced and which must be protected. Demand response may create revenue, but the article presents it as a consequence of preparation, not a substitute for it. The limits are equally clear: some loads cannot be interrupted without crop risk; the available reduction depends on crop, stage and season; and the approach relies on advance agreements and tested controls. The article recommends asking the utility where the site falls in its plan, then starting to make a plan.