When a utility grid runs short of power, the outage plan that matters to a greenhouse may begin on the utility bill. In California, bills include a rotating outage group or block that shows where a customer stands in line if the grid cannot meet demand. Ian Knisely, an energy analyst at Energy Bridge Advisors, notes that every grower has a place in that line, whether or not the number is printed on the bill.
The distinction is not cosmetic. Federal reliability standards, including NERC’s EOP-011, require grid operators nationwide to maintain emergency plans for cutting load. Utilities across the country keep such plans for times when supply cannot meet demand. When a plan is implemented, power is shut off systematically, often with only minutes of warning. Hospitals and other critical facilities are protected where possible. Almost everyone else, including greenhouses, is exposed.
California is unusual in printing the rotating outage information directly on the utility bill. That makes the utility’s queue visible to the customer. In other markets, the same kind of queue can exist without appearing on a bill. For a grower, the practical question is not only whether the information is printed, but whether the greenhouse has its own plan for the moment the grid operator reaches its site.
Rolling outages have hit several regions in recent years during heat waves and winter storms. For a greenhouse, a sudden loss of power can take down fans, pumps, irrigation, heating and controls at the worst possible time. The utility has a detailed plan for that day. Most greenhouses do not.
Outage versus curtailment
The difference between an outage and a curtailment 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. A curtailment plan is a written playbook for the hours when the grid is stressed. Knisely describes four steps.
1. Inventory the loads
The first step is to list the major equipment and roughly how much power each piece draws. That covers supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and any cold storage. The list creates the basis for deciding what can be switched off, what can be reduced and what must remain available.
2. Sort loads by crop risk
Not all equipment has the same priority. Some loads can be dropped entirely for a few hours without harm to the crop. Some can be reduced: lights can be dimmed, fans staggered, or a setpoint adjusted by a few degrees. Some must stay on no matter what, including controls, alarms and whatever keeps the most sensitive crop alive. The sorting depends on what is grown and at what stage, so it can change through the season.
3. Use forecasts as triggers
The outage order may arrive with only 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 a trigger. 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. Either way, the crop enters the hard hours with some margin.
4. Assign and automate the response
The plan also needs people and procedures. It should decide who receives the alert, who makes the decision and who carries it out. If the environmental controller can run the sequence automatically, it should be programmed and tested. A plan that depends on one person answering a phone at 4 p.m. on a Saturday is not a plan.
From curtailment to demand response
Once those steps are done, the grower should know how many kilowatts can be given up, for how long, and at what cost to the crop. That number is what the grid is willing to pay for. Before ordering outages, utilities and grid operators will 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 market is demand response. It exists in most of the country, largely so the outage plan never has to be used.
Demand response does not replace the need for an outage plan. It gives the grower a measured way to participate before the grid reaches an emergency. The value comes from knowing the load, the duration and the crop risk in advance, rather than discovering them when the power is already off. For a controlled-environment operation, that is also an operational boundary: flexibility is useful only when the crop can tolerate the reduction and the remaining systems can protect the crop.
The approach has limits. A curtailment plan does not make a greenhouse immune to outages, and it does not turn every load into a flexible one. It depends on the crop, its stage and the season. But it gives the grower a way to decide what stops first, what can be reduced and what must be protected, rather than leaving those choices to a utility’s emergency order.
The practical next step is to ask the utility where a site falls in its plan, and then to start making a plan for the greenhouse. The utility may have an outage plan; the grower needs a curtailment plan.