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Keep a greenhouse operating through an outage by deciding in advance which systems are essential, sizing backup power for both running and motor-starting demand, and preparing for the season’s main risk. Winter plans often center on heat and heater controls; warm-weather plans may depend on ventilation, cooling, pumps, and irrigation. There is no reliable one-size-fits-all generator size: the right setup depends on the equipment that must run together and how it is connected.
Choose essential loads for the season
Start by listing the equipment whose loss would put crops or facility safety at risk. The priority list changes with weather and production conditions, so make a separate plan for cold-weather and warm-weather outages.
Cold-weather priorities
Identify the heating equipment and controls needed to protect crops, along with any pumps or other systems required to keep heating operational. Plan for a heating failure as well as a grid failure: Alberta Agriculture and Irrigation recommends a complete heating-failure plan, including knowing where emergency heating equipment could be rented. Alberta’s greenhouse best-management guide also distinguishes backup capacity for critical equipment from capacity for all systems.
Warm-weather priorities
List ventilation fans, cooling equipment, well or water pumps, and irrigation systems that need power to keep conditions stable. Cornell Cooperative Extension’s Greenhouse Engineering, NRAES-33 discusses how outage concerns vary by season. UGA Cooperative Extension also addresses greenhouse and crop storm damage in its storm guidance.
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Size backup power for the loads that must run together
Inventory each essential electrical load before choosing a generator. Record equipment nameplate information, including voltage, phase, horsepower where applicable, running current, and starting requirements. Decide which loads must operate simultaneously and which can be shut off or delayed. UF/IFAS Extension’s Auxiliary Power Units For Greenhouse Operations, revised in 2021 and reviewed in 2024, recommends estimating essential simultaneous loads and accounting for the power needed to start as well as operate them.
| Equipment to assess | What to record or decide |
|---|---|
| Ventilation fans | Motor voltage, phase, running current, starting demand, and which fans must operate together. |
| Well and water pumps | Electrical nameplate details, starting requirements, and whether water delivery can be interrupted. |
| Heaters and heater controls | Which heat sources and controls are essential for the current crop and weather conditions. |
| Cooling and irrigation equipment | Which components must run during an outage and which can be shed or delayed. |
| Other site-critical equipment | Include only equipment whose loss creates a meaningful crop or facility risk. |
Account for motor starting
UF/IFAS notes that motor starting amperage may be two to seven times running current. That is a rule of thumb, not a universal multiplier. The publication also gives a rough screening rule of about three times the wattage of the largest motor to start it; confirm generator suitability against the generator manufacturer’s guidance and the actual combination of voltage, motor phase, and loads.
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For its own illustration, UF/IFAS estimates that a 5-kilowatt generator at 230 volts produces 21.7 amperes. This is an electrical example, not a recommendation for greenhouse capacity. The source identifies well pumps and ventilation fans as common large loads.
Compare backup approaches by coverage and constraints
A generator intended to power every greenhouse system has a different capacity requirement from one intended only for critical equipment. Before choosing, compare the coverage needed, simultaneous loads and starting demand, fuel availability for the expected outage, and the requirements for a safe, compliant installation. Have a qualified electrician review the actual standby design and transfer arrangement.
Prepare the generator, connection, and site
A standby generator needs a suitable transfer arrangement; it should not be connected to greenhouse wiring through an improvised setup. Cornell’s Greenhouse Engineering, NRAES-33 covers installation considerations including transfer switches, generator location, and exhaust. Review utility requirements and local codes with a licensed electrician, and route exhaust outdoors from a dry, accessible generator location.
Fuel and maintenance are part of readiness, not details to handle after an outage begins. The University of Connecticut Extension advises keeping adequate fuel and operating the generator monthly in Prepare Your Greenhouses for Weather Events. Its farm-weather guidance also recommends seasonal checks and regular maintenance. Follow the generator manufacturer’s operating and service instructions.
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Use alarms and assign response responsibility
A battery-powered temperature alarm can warn staff when conditions move outside an acceptable range. UGA Cooperative Extension notes this option in Greenhouses: Heating, Cooling and Ventilation. Decide who receives the alert, who can reach the site, and who is authorized to act. Keep contact details and operating instructions accessible to the people responsible for the response.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Write an outage response sequence for your site
The correct startup and shutdown order depends on the greenhouse’s wiring and equipment. Write and post a sequence based on the installed system’s instructions rather than relying on a generic switching order. A plan can use this framework:
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- Confirm the outage and assess immediate temperature, heating, ventilation, and water risks.
- Reduce or disconnect nonessential loads according to the site plan.
- Bring backup power online using the installed equipment’s instructions.
- Start large motors sequentially; avoid starting several large motors at once.
- Check that critical heating, ventilation, and water systems are actually operating.
- Monitor greenhouse temperature and water delivery, and contact the utility or relevant service provider.
- After utility power returns, continue checking crop and facility conditions and restore normal operation according to the site plan.
Complete a continuity checklist before the next outage
- List vulnerable electrical equipment and define essential loads separately for cold and warm conditions.
- Calculate capacity from simultaneous loads and motor-starting demand; confirm the design with equipment manufacturers and a qualified electrician.
- Install an appropriate transfer arrangement and verify generator location and outdoor exhaust routing against utility requirements and local codes.
- Keep adequate fuel for the anticipated event, run the generator monthly, and follow a routine inspection and maintenance schedule.
- Test temperature alarms and identify who receives alerts and responds.
- Write an emergency heating plan, including contacts for rental heating equipment if winter production continues.
- Keep operating instructions and a contact list accessible to staff.
The University of Connecticut Extension’s Preparing Farm Operations for Extreme Weather: General Strategies for Producers recommends identifying vulnerable systems and backup plans ahead of an event.
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