Commercial greenhouse operators routinely plan for weather, pests and crop schedules, but many leave one operational risk to the utility: a sudden loss of power. Energy analyst Ian Knisely, who advises controlled-environment agriculture operators on utility costs, argues that growers should know where their site sits in a grid emergency and prepare their own plan for cutting electrical load.
Knisely points to a detail on California utility bills: the customer’s rotating outage group or block. That designation shows where a site falls in line if the grid runs short. Every grower has a place in that sequence, he writes, whether or not the bill displays it. Federal reliability standards, including NERC’s EOP-011, require grid operators across the country to maintain emergency plans for cutting load, but California is unusual in printing the information on utility bills.
Those plans are designed to protect critical facilities such as hospitals where possible. Other customers, including greenhouses, can still lose service, often with only minutes of warning. Rolling outages have affected several regions in recent years during heat waves and winter storms. For a greenhouse, the consequence is simultaneous loss of fans, pumps, irrigation, heating and environmental controls at a time when the crop is most vulnerable.
Outage versus curtailment
The distinction between an outage and a curtailment is control. In an outage, equipment stops at once. In a planned curtailment, the grower decides in advance which loads to shed, how much to reduce them and which systems must remain on to protect the crop. Knisely describes a curtailment plan as a written playbook for periods when the grid is under stress, organized around four steps.
Build the load inventory
First, list major equipment and estimate its approximate power draw. The inventory should cover supplemental lighting, fans, evaporative cooling, heating, pumps, dehumidification, controls and any cold storage. This gives the grower a map of where electricity is used and which systems are most important during an emergency.
Sort loads by crop risk
Next, classify each load. Some equipment can be shut off entirely for a few hours without harming the crop. Others can be reduced by dimming lights, staggering fan operation or shifting a temperature setpoint by a few degrees. A third group must stay on regardless, including controls, alarms and whatever keeps the most sensitive crop alive. The sorting depends on the crop and its growth stage, so the plan may need to change through the season.
Use forecasts as a trigger
An outage order may arrive with little notice, 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 a trigger. In summer, they can pre-cool in the morning, irrigate early and close shade curtains before the afternoon peak. In winter, they can heat ahead of the cold peak, close thermal curtains early and confirm that backup heat is fueled and tested. The aim is to bring the crop into the difficult hours with some margin.
Assign roles and automate
The final step is to 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 relies on a single person being available by phone on a weekend is not a workable plan, Knisely writes.
Once these steps are complete, a grower should know how many kilowatts can be surrendered, for how long and at what cost to the crop. That number matters beyond emergency preparation. Utilities and grid operators pay customers that agree in advance to cut load before they order outages, because a megawatt removed on request is cheaper than one bought at emergency prices. The arrangement is known as demand response and exists in most of the country, largely to avoid using the outage plan.
Knisely advises growers to ask their utility where their site falls in its emergency plan, then start making their own. The broader point is that a greenhouse’s resilience depends on decisions made before the grid fails, not only on the utility’s schedule for restoring power.