Industry Application
Commercial indoor growing requires an LED lighting system designed around crop-specific DLI targets, canopy PPFD, photoperiod, fixture efficiency, light uniformity and operating cost. Because an indoor room receives no daylight, every photon the crop uses has to be bought, so the planning sequence runs from target DLI to delivered PPF to fixture count — never from watts per square metre.
Illustrative image of a typical commercial indoor growing environment — not a customer installation photograph.
Technical focus on this page
DLI-led fixture sizing, uniformity and cost of delivered light
How this application works
A sealed indoor room removes the two variables greenhouse growers rely on: daylight and season. That makes the lighting design fully deterministic, and it also makes every design error permanent. Once the fixtures are hung, spacing, mounting height and circuit layout fix the light distribution for years, and the electricity bill follows the installed load every single day.
The practical consequence is that the useful unit of comparison is not the fixture wattage but the delivered photons per unit of energy — PPF in µmol/s and PPE in µmol/J — combined with how evenly those photons land on the canopy. Two fixtures with the same wattage can differ by a third in PPF, and a layout with good average PPFD but poor uniformity can still produce uneven crops.
Efficacy also has a physical ceiling, which is useful when a supplier quotes a spectacular number. A published review of LED physics and fixture design put the practical limit at about 3.4 µmol/J for white-plus-red fixtures and 4.1 µmol/J for blue-plus-red, with both figures falling by roughly 10 % once optical protection for humid environments is added (Kusuma, Pattison & Bugbee 2020). A quoting sheet claiming substantially more than that is describing a measurement method, not a fixture.
The sequence below is the one this page walks through: set the crop and stage targets, convert them into a total PPF requirement, size the fixture count with a utilisation margin, verify uniformity at the planned mounting height, then check power density against HVAC capacity and utility budget.
Application challenges
These are the constraints that decide whether a lighting plan survives contact with an operating facility.
With no free daylight, the annual lighting energy is simply installed load × photoperiod × 365. A 10% loss in fixture efficacy is therefore a permanent 10% addition to the largest controllable operating cost in the room — which is why PPE and lumen-per-watt marketing claims must be separated before comparing quotes.
A room can average the target PPFD while edge benches and aisle ends sit far below it. Plants in low-light positions stretch, mature later and distort scheduling. Uniformity is a layout outcome — mounting height, fixture spacing, beam angle and wall reflectance — not a fixture specification on its own.
Indoor fixtures reject most of their input power as heat inside the conditioned envelope. Power density decisions are therefore HVAC decisions: raising PPFD by adding fixtures adds both electrical load and the cooling needed to remove that heat.
Propagation, vegetative and flowering zones need different PPFD and photoperiod. If the only control is a wall switch, the room can only run one recipe. Dimming and zone control have to be specified at design time, because retrofitting control protocols into sealed fixtures is rarely practical.
Replacing HPS one-for-one by wattage usually overshoots or undershoots the delivered PPFD, because HPS and LED distribute light differently and modern LED fixtures deliver more PPF per watt. Retrofit planning starts from measured PPF of the existing fixtures, not from their nameplate wattage.
Lighting requirements
Each metric below has to be set from the crop, structure and operating practice — not from a generic watts-per-square-metre rule.
| Parameter | Planning target | Why it matters |
|---|---|---|
| Daily light integral (DLI) | Crop and stage specific; commonly quoted planning ranges are ~12–17 mol/m²/day for lettuce and leafy greens, ~20–30 for fruiting crops, higher for high-light flowering crops | DLI is the total photon dose per day and is the number the crop actually responds to — the quantity behind the DLI research review and the national DLI maps of the United States (Faust & Logan 2018). It combines PPFD and photoperiod into one target. |
| Canopy PPFD | Derived from DLI and photoperiod: PPFD = DLI ÷ (photoperiod × 0.0036) | PPFD is the instantaneous intensity at canopy level; it is the specification a fixture layout must actually deliver. |
| Photoperiod | Typically 14–20 h for vegetative production; 12 h for photoperiod-sensitive flowering | Longer photoperiod lowers the PPFD needed for the same DLI, but adds energy and can affect morphology and flowering. |
| Uniformity | Aim for a minimum-to-average ratio of about 0.8 or better across the usable canopy | Uniformity determines whether the weakest plants limit the batch. Measure on a grid, not at one point. |
| Fixture efficacy (PPE) | Compare µmol/J at the same PPF class; higher PPE reduces kWh for the same delivered light | Efficacy converts photons into operating cost. It matters more in indoor rooms than anywhere else. |
| Mounting height and spacing | Set by beam distribution and target uniformity; verify with a PPFD grid at canopy level | Raising fixtures improves uniformity but loses intensity; the two must be balanced against ceiling height. |
| Dimming and control | 0–10V, PWM or multi-channel per zone, with scheduling | Stage recipes, sunrise/sunset ramps and load shedding all depend on controllable output. |
| Ingress protection | IP54 minimum for dry rooms; IP65 where washdown, misting or high humidity applies | Irrigation and sanitation practice decide the enclosure rating, not the marketing sheet. |
Reference data
Planning references compiled from horticultural lighting literature and standards. They are starting points for your own trials, not guarantees of performance.
| Crop | Typical DLI (mol/m²/day) | PPFD at 16 h (µmol/m²/s) | Planning note |
|---|---|---|---|
| Lettuce / leafy greens | 12 – 17 | 210 – 295 | Above the upper range, tipburn and bolting risk rise; airflow matters as much as intensity |
| Culinary herbs (basil, mint) | 15 – 25 | 260 – 435 | Basil responds strongly to DLI; keep uniformity tight or canopy height varies |
| Microgreens | 6 – 12 | 105 – 210 | Short cycles; light is rarely the limiting factor compared with tray density |
| Tomato / pepper (indoor) | 20 – 30 | 350 – 520 | Fruiting crops need high DLI plus CO₂ and VPD control to use it |
| Strawberry (indoor) | 15 – 25 | 260 – 435 | Photoperiod interacts with cultivar; verify before committing to a recipe |
| High-light flowering crops | 30 – 45+ | 520 – 780+ | Only economical with CO₂ enrichment, tight climate control and high PPE fixtures |
PPFD column converted as PPFD = DLI ÷ (photoperiod × 0.0036) at 16 h. Planning ranges compiled from horticultural extension and research literature; the DLI concept and its measurement are reviewed in Faust & Logan (2018). Cultivar, CO₂, VPD and root-zone conditions all shift the optimum — treat these as starting points for your own trials, not as standards.
| Line item | HPS 1,000 W (double-ended) | LED bar ~720 W class | What to check in a quote |
|---|---|---|---|
| Typical PPF | ~1,700 – 2,100 µmol/s | Comparable or higher PPF at lower input power | Measured PPF report, not a calculated estimate |
| Efficacy | ~1.7 µmol/J (measured) | ~2.6 – 3.0 µmol/J class | PPE at the same drive current as the quoted configuration |
| Heat into the room | High radiant and convective load | Lower total load, different distribution | Cooling capacity per m² of canopy |
| Distribution | Broad, requires wide spacing | Directed bars, closer spacing | PPFD grid at planned mounting height |
| Control | Contactor / relay switching | 0–10V or PWM dimming per zone | Protocol, channel count, controller compatibility |
Method comparison only. Measured efficacy of 1,000 W double-ended HPS and the best LED fixtures available at the time was reported as 1.66–1.70 µmol/J for both, against 1.02 µmol/J for a 1,000 W mogul-base HPS and 1.46 µmol/J for ceramic metal halide (Nelson & Bugbee 2014); LED bar fixtures have improved since that dataset, while HPS has not. Actual figures depend on the specific fixtures and tariffs you are comparing.
Lighting system design
The order matters: geometry and targets first, fixture count second, verification and control last.
Write down one target per zone. A single room running several stages will always compromise one of them; if the schedule needs both propagation and flowering, plan them as separate lighting zones with separate control.
Divide DLI by photoperiod and by 0.0036. A 16-hour photoperiod at 30 mol/m²/day needs roughly 520 µmol/m²/s; the same DLI over 20 hours needs about 417 µmol/m²/s, at the cost of four more hours of load.
Multiply canopy PPFD by canopy area, divide by a utilisation factor of roughly 0.8 to account for wall losses, spill and non-uniformity, then divide by the fixture PPF. Round up by rows, not by single fixtures, so spacing stays regular. Treat the utilisation factor as a planning allowance rather than a measured property of the room: it exists only until a PPFD grid at the planned mounting height replaces it.
Set fixture spacing and mounting height together, check the edge rows against the walls, and request a PPFD grid at canopy level from the supplier. Reflective walls help, but they do not fix spacing that is already too wide.
Divide installed wattage by canopy area to get W/m². That number sets both the electrical circuit design and the cooling load, and it is the fastest way to catch a lighting plan that is technically correct but operationally unaffordable.
Decide dimming protocol, zone grouping, IP rating for your irrigation practice, and how fixtures will be cleaned and serviced. These four items cause most post-installation complaints and cannot be added later at low cost.
Worked example
Illustrative example — assumptions stated below, not client data
| Step | Calculation | Result |
|---|---|---|
| Daily light integral check | DLI = 450 × 18 × 0.0036 | 29.2 mol/m²/day — the top of the fruiting-crop planning range, so confirm CO₂ and VPD can support it |
| Delivered PPF at canopy level | 450 µmol/m²/s × 300 m² | 135,000 µmol/s |
| Installed PPF including utilisation allowance | 135,000 ÷ 0.8 | 168,750 µmol/s of installed PPF |
| Fixture count | 168,750 ÷ 810 µmol/s per fixture | 208.3 → round up to 209 fixtures |
| Spacing sanity check | 300 m² ÷ 209 fixtures | 1.44 m² per fixture — about 1.2 × 1.2 m centres; confirm that is buildable around doors and aisles |
| Power density | 209 × 300 W ÷ 300 m² | 209 W/m² installed — a cooling load as much as an electrical one |
| Daily lighting energy | 209 × 0.3 kW × 18 h | 1,128.6 kWh/day for the room |
Every number above sits on one assumption set: target PPFD, canopy area and fixture PPF. Change the fixture to a 400 W model and the count, the W/m² and the kWh all move together — which is why a quote that states a fixture count without stating its PPF and input power cannot be checked. This is a photon budget, not a lighting design, and it is not a verified PPFD.
Three different kinds of number
The worked example above is an initial estimate. It is not a lighting layout, and it is not a verified PPFD. Keeping the three apart is what stops a photon budget from being quoted as delivered performance.
The photon budget above: target PPFD × canopy area ÷ utilisation allowance ÷ fixture PPF.
Arithmetic only. Enough to size an enquiry, an electrical allowance or a sanity check on a supplier quote — and explicitly not a performance promise.
Fixture positions, mounting height, beam angle, wall reflectance and aisle edges converted into a predicted PPFD grid.
A design deliverable: a PPFD map at canopy height, with average, minimum-to-average ratio and the measurement height all stated.
PPFD measured on a grid in the built room, at the documented mounting height and dimming level, with a calibrated quantum sensor.
Measurement data only. This is the only stage that may be described as delivered performance, and it must be repeated after any change of spacing, mounting height or dimming setting.
Fixture selection
Selected from the six fixture categories we manufacture; the right mix depends on ceiling height, canopy structure and control requirements.
Primary overhead lighting for main canopy rooms
Bar arrays spread output across a wide footprint, which is what large rooms need for even coverage; foldable frames cut freight volume for distributor and project orders.
Low-ceiling rooms, veg rooms and small zones
A compact board concentrates high PPF into a small footprint, which suits rooms where ceiling height limits mounting distance or where zones are narrow.
Dense canopies and multi-tier benches
Overhead light alone cannot reach the lower third of a tall, dense canopy; slim bars placed inside the canopy raise the light level where fruit set and leaf quality are decided.
Real products
Specifications shown are the confirmed values from each product record. Where a parameter is not confirmed by the source material, it is not displayed here.
800W folding bar fixture, 160 lm/W Samsung diodes, 1100 × 1100 mm or 1800 × 1100 mm open frame.
View product details
100/200/300W board with a published per-tier table: 220, 451 and 810 µmol/s at 2.1, 2.2 and 2.7 µmol/J.
View product details
150W three-sided intercanopy bar, 1156 mm, 18,000 lm, IP65, rope or bracket mount.
View product detailsOEM & ODM
We build fixtures to a specification, document what was built, and support the certification and packaging work that a private-label programme needs.
Common mistakes
Each of these shows up after installation, when the layout is already fixed and the circuits are already run.
| Mistake | What to do instead |
|---|---|
| Buying by watts per square metre | Convert to PPF and PPE first. A 30 W/m² difference means nothing until you know µmol/J and µmol/s per fixture. |
| Quoting average PPFD without a uniformity grid | Ask for a PPFD map at your planned mounting height and spacing, and compare the minimum value, not just the average. |
| Ignoring the cooling load added by lighting | Add the lighting wattage to the room heat balance before finalising PPFD targets; otherwise the HVAC will not hold VPD at peak load. |
| Over-lighting a room that lacks CO₂ and VPD control | Match PPFD to the rest of the environment. Light above what the plants can use is paid for twice — in electricity and in cooling. |
| Specifying fixtures with no dimming or zone control | Plan stage recipes and sunrise/sunset ramps at design time; control protocols cannot be retrofitted cheaply. |
Related technical guides
Published articles that explain the measurement and selection logic used on this page.
Buying Guide
A commercial buyer’s framework for choosing LED grow lights: match crop PPFD and DLI targets, fixture efficacy (µmol/J), uniformity, spectrum, dimming, IP rating and total cost of ownership.
Read the guideBuying Guide
A practical framework for specifying grow lights on a commercial indoor farm — from PPFD targets and uniformity to efficacy, controllability and total cost of ownership.
Read the guideTechnology
PPF and PPFD are the two most quoted numbers on a grow light spec sheet — and the two most commonly confused. Here is what each one measures and how to use them.
Read the guideRelated articles
In-depth guides written for this application — planning, spectrum, DLI and layout.
Indoor Growing
A practical method for laying out LED grow lights in a commercial indoor farm — fixture spacing, mounting height, overlap and uniformity — with a worked fixture-count calculation and a planning checklist.
Read Article
Indoor Growing
How to set a Daily Light Integral for indoor leafy greens, herbs and microgreens under LED — convert DLI to PPFD, avoid overshooting, and read real extension references.
Read Article
Indoor Growing
Why photoperiod and spectrum control matter for indoor crop consistency, how dimming and scheduling work, and how to avoid the most common controllability mistakes.
Read ArticleEvery technical figure on this page is traceable to one of the sources below. Each entry gives the publication, its author or issuing body and year, a resolvable link, and the specific claim on this page that it supports — an institution name on its own is not evidence, and no manufacturer marketing material is used here as independent research. All links were checked and resolved on 19 October 2026.
Kusuma P., Pattison P.M. & Bugbee B., Horticulture Research 7:56 (2020)
Supports on this page: The 3.4 µmol/J (white + red) and 4.1 µmol/J (blue + red) ceiling for LED fixture efficacy, and the ~10% reduction once optical protection is added.
Nelson J.A. & Bugbee B., PLoS ONE 9(6): e99010 (2014)
Supports on this page: The measured efficacy figures in the HPS-versus-LED comparison table (1.66–1.70 µmol/J for double-ended HPS and the best LED of that period, 1.02 µmol/J for mogul-base HPS, 1.46 µmol/J for ceramic metal halide).
Faust J.E. & Logan J., HortScience 53(9): 1250–1257 (2018)
Supports on this page: DLI as the cumulative daily photon dose and the quantity crop scheduling is built on, plus the note that the PPFD column in the crop table is a conversion of DLI, not an independent target.
American Society of Agricultural and Biological Engineers, standard S640 JUL2017 (reaffirmed 2022)
Supports on this page: The definitions and units used throughout this page: PPF in µmol/s, PPFD in µmol/m²/s, DLI in mol/m²/day, and PPE in µmol/J.
DesignLights Consortium, technical requirements effective 18 April 2025
Supports on this page: The requirement to compare efficacy and quality metrics at a defined fixture class and test configuration rather than from a headline number — the basis for the “what to check in a quote” column.
Where a source could not be confirmed as publicly accessible, the claim it would have supported has been written as a lower-certainty statement rather than given a citation. Planning ranges remain starting points for your own trials — they are not guarantees of performance, and no figure on this page is a quotation.
Industry FAQ
Specific follow-up questions about this application, answered directly and then explained.
Send the growing area, crop and stage, target PPFD or DLI, ceiling or layer height and your market requirements. We will come back with a fixture proposal, a layout suggestion and the documentation you need to evaluate it.
