Buy photons, not fixtures.

Daily light integral, or DLI, describes the total photosynthetically active light received over a day. It answers a different question from one instantaneous intensity reading. Measure at crop height across representative locations and across the production period before deciding how much supplemental light is missing.[1][2]

The target is crop, stage, cultivar, environment, and production-goal specific. A fixture cannot be “best” without those constraints. Ask what canopy DLI and uniformity the design is intended to deliver, under what mounting height and room conditions.

A room average can hide shaded edges and hot spots. Build a grid at canopy height, record PPFD at each point under a defined lighting state, and calculate uniformity. Repeat after crop height, racks, reflective surfaces, or fixture positions change. Keep the measurement instrument and date in the record.[1]

Spectrum can influence crop responses, but it does not remove the need to deliver and measure an appropriate quantity of light. Compare fixtures using third-party performance data where available, while keeping electrical input, controls, lifetime assumptions, and the actual layout visible.[3]

Purdue's greenhouse-lighting economics framework compares the cost of adding light with the value of the crop response. That is the right structure even when local values differ. Include fixture and installation cost, electrical demand, operating hours, demand charges, maintenance, cooling or heating interaction, usable growing area, and the expected marketable response.[2][4]

• Measure current canopy DLI by season or representative production condition.
• Define crop-, stage-, and cultivar-specific production objectives.
• Model the layout and verify PPFD and uniformity after installation.
• Calculate energy and HVAC interaction using local tariffs and operating schedules.
• Run a bounded trial before projecting the response across the facility.

Compare like crop stages, density, climate, irrigation, nutrition, harvest method, and market grade. Record fresh and saleable yield, cycle time, quality, energy, and rejected product for both the test and reference. A percentage without the baseline, area, time, and energy denominator is not a business result.

Do not promise that a light will double yield. Crop response can be limited by temperature, carbon dioxide, nutrition, root health, density, or market specifications even when light was previously limiting.[4]

The lighting record should connect delivered photons to electrical energy and marketable crop output. That is how a grower learns whether a fixture, schedule, or layout is producing value rather than merely producing light.