Quick Answer: Container greenhouse supplemental lighting in Ontario closes a 76 percent winter light deficit by adding 8 to 20 mol per square metre per day of supplemental DLI, usually from LED fixtures running 2.7 to 3.0 micromoles per joule. A 40ft container growing leafy greens needs roughly 1,800 to 2,400 watts of LED on a 240V circuit, and structuring a 16-hour photoperiod into Ontario off-peak hydro hours keeps the running bill in check. Every build is sized to the crop, the container, and the panel. Reach Paul or Christian at the Brantford yard for an honest delivered quote.
In This Guide
- How big is the winter light gap inside an Ontario container greenhouse?
- What DLI and PPFD does each crop need?
- Is LED or HPS better for a 40ft container greenhouse?
- How many watts of grow light does a 20ft or 40ft container need?
- What circuit and panel size does the lighting load require?
- What does a winter photoperiod cost in Ontario hydro?
- How does photoperiod timing cut the hydro bill?
- How much heat and humidity do the lights add?
- Which fixtures, drivers, and dimming controls should you choose?
- What are the container install realities for ceiling height and mounting?
- FAQs
Reading Time: 14 minutes
How big is the winter light gap inside an Ontario container greenhouse?
The winter light gap inside an Ontario container greenhouse is roughly a 76 percent shortfall. By late November the daily light integral falls to about 4 mol per square metre per day inside a glazed container, below the 16 to 20 mol most crops need. Supplemental LED lighting adds back 8 to 21 mol to keep crops growing through winter.
A container greenhouse in Brantford, Norfolk, Welland, or anywhere south of Bracebridge runs into the same wall every November. The sun drops below the treeline by 4:30. Cloud cover settles in for 60 percent of December days. The daily light integral (DLI) inside a glazed container greenhouse falls to roughly 4 mol per square metre per day by late November, a 76 percent shortfall against what a tomato crop needs. Leafy greens slow growth; tomatoes and peppers stop fruiting entirely. That gap is what supplemental lighting closes, and it is what every Ontario operator wrestles with from October through March.
This matters more in a container than in a poly-tunnel because of geometry. A 40ft container greenhouse gives 320 square feet of growing floor under either an 8ft 6in standard ceiling or 9ft 6in high cube. A 20ft halves the floor to 160 sqft with the same ceiling. The narrow geometry pushes every supplemental light closer to the canopy than a traditional greenhouse install, which changes wattage selection, drives heat-management decisions, and forces honest electrical math before you order a fixture.
Van Blanc has been delivering containers from our 4 Brantford yards since 1995, including a steady stream of greenhouse builds across Norfolk, Niagara, Grand River Valley, and Wellington. Paul has watched the supplemental-lighting conversation evolve from 1000W HPS bulbs to today’s 600W LED arrays that produce the same canopy intensity at half the electrical load. If you are still deciding on glazing, insulation, and crop layout, the companion piece on building a year-round growing container in Ontario covers the box itself; this guide walks through the lighting so the order list matches the container, the crop, and the panel you are plugging into.
Christian LeBlanc, second-generation operator: “People call about the container and the second question is always the lights. I tell them the same thing my dad tells them: pick the crop first, then we size the box and the wattage around it. A 20ft of lettuce and a 40ft of tomatoes are two completely different electrical conversations, and you want that sorted in the yard, not after the bin lands.”
What DLI and PPFD does each crop need?
DLI and PPFD targets vary by crop, and two numbers drive every supplemental-lighting decision: PPFD (instantaneous canopy intensity in µmol/m²/s) and DLI (cumulative photon dose in mol/m²/day). DLI equals PPFD times photoperiod hours times 0.0036. A target DLI of 20 mol with a 16-hour photoperiod requires a sustained PPFD of about 347 µmol. That is the math every fixture spec sheet is trying to deliver.
Targets shift by crop. Leafy greens thrive at 15 to 20 mol DLI with PPFD 200 to 400. Culinary herbs target 12 to 15 mol DLI but appreciate the higher end for leaf colour. Tomatoes, peppers, and cucumbers want 22 to 30 mol DLI with PPFD 600 to 900 at fruit set. Cannabis sits at the top, 35 to 45 mol DLI with PPFD pushing 1,000 in flower.
| Crop category | Target DLI (mol/m²/day) | Target PPFD (µmol/m²/s) | Ontario winter supplemental need |
|---|---|---|---|
| Lettuce, spinach, kale (leafy greens) | 15 to 20 | 200 to 400 | 11 to 16 mol supplemental |
| Basil, parsley, cilantro (herbs) | 12 to 15 | 200 to 350 | 8 to 11 mol supplemental |
| Tomato, pepper (vegetative) | 20 to 25 | 400 to 700 | 16 to 21 mol supplemental |
| Tomato, pepper (fruit set) | 22 to 30 | 600 to 900 | 18 to 26 mol supplemental |
| Cucumber, strawberry | 15 to 25 | 400 to 700 | 11 to 21 mol supplemental |
| Cannabis (flowering) | 35 to 45 | 800 to 1,200 | 31 to 41 mol supplemental |
The supplemental need column assumes 4 mol of natural DLI on a typical Ontario winter day. The number ranges from 2 mol on heavy-cloud December to 8 mol on bright late-February. Dynamic dimming covers the spread, which is why modern LED builds pair with a 0-10V dimmable driver. Growers running soil-free systems should also read how the lighting plan changes when the crop sits on a soil-free vertical rack inside the box, since stacked canopies multiply the photon demand per square foot of floor.
Is LED or HPS better for a 40ft container greenhouse?
For a 40ft container greenhouse, LED is the better choice on every metric except upfront fixture cost. For two decades the default supplemental light in Canadian greenhouse production was the 1000W high-pressure sodium (HPS) double-ended fixture. The case against HPS was always efficiency. A single-ended 1000W HPS produces 1.7 to 1.9 µmol/J. A double-ended HPS pushes to 2.0 to 2.1 on a good day. Modern LED arrays from Fluence, Gavita, Heliospectra, and P.L. Light deliver 2.7 to 3.0 µmol/J consistently, premium tier reaching 3.5. The result is roughly 40 to 50 percent lower lighting hydro for the same canopy PPFD, plus minimal radiant heat. In a 40ft container the LED’s cool operation removes one of HPS’s biggest drawbacks: a 1000W HPS dumps about 700W of waste heat into the canopy zone.
| Fixture class | PPE (µmol/J) | Watts to hit 400 PPFD (40ft canopy) | Radiant heat into canopy | Relative upfront outlay |
|---|---|---|---|---|
| Single-ended HPS 1000W | 1.7 to 1.9 | 4 fixtures, 4,000W total | High (~70 percent of wattage) | Lowest per fixture, highest lifetime hydro |
| Double-ended HPS 1000W | 2.0 to 2.1 | 3 to 4 fixtures, 3,600W | High | Low per fixture, high lifetime hydro |
| Commercial LED 600W | 2.7 to 3.0 | 4 fixtures, 2,400W total | Low (~30 percent of wattage) | Higher per fixture, far lower lifetime hydro |
| Premium LED 600W | 3.0 to 3.5 | 3 to 4 fixtures, 1,800 to 2,400W | Low | Highest per fixture, lowest lifetime hydro |
The capital-cost gap closes inside three to four winter seasons on hydro savings alone, before avoided HVAC load. For new builds, LED is the honest call unless you have HPS hardware on hand. The Agriculture and Agri-Food Canada Harrow Research and Development Centre in Leamington publishes practical commercial recommendations covering HPS, LED, and hybrid setups for Ontario growers.
Why Norfolk and Niagara operators went LED first
Norfolk cannabis growers and Niagara vegetable producers were among Ontario’s first commercial LED adopters because their crops sit at the high-DLI end. At 35 mol of supplemental DLI, the 40 percent hydro savings from LED pays back the capital premium in two crop cycles. For leafy-greens at 10 to 15 mol the payback stretches to four winters, but LED still wins on heat management and dimming flexibility.
How many watts of grow light does a 20ft or 40ft container need?
Grow-light wattage for a container build comes straight from canopy demand, and working backwards from that demand to fixture count is the cleanest sizing method. For a 40ft container with 320 sqft of canopy (29.7 m²) running leafy greens at 300 PPFD, canopy demand is 8,910 µmol per second. A 600W LED at 2.85 µmol/J delivers about 1,710 µmol per second of PPF, so roughly 5 fixtures, 3,000W total. Most builds spec 6 fixtures running at 80 percent dim for even coverage: 2,880W draw. A 20ft container halves to 3 fixtures. A 40ft tomato build at 600 PPFD needs 10 to 12 fixtures at 6,000 to 7,200W. Cannabis at 1,000 PPFD pushes to 14 to 16 fixtures, 8,400 to 9,600W, almost a 50A 240V circuit for the lights alone.
| Container + crop scenario | Fixtures (commercial 600W LED) | Total wattage | Recommended circuit |
|---|---|---|---|
| 20ft, leafy greens, 300 PPFD | 3 fixtures | 1,440 to 1,800W | 1 x 20A 240V (or 2 x 15A 120V) |
| 40ft, leafy greens, 300 PPFD | 6 fixtures at 80 percent | 2,880W | 1 x 20A 240V |
| 40ft, herbs, 250 PPFD | 5 fixtures at 70 percent | 2,100W | 1 x 20A 240V |
| 40ft, tomato/pepper, 600 PPFD | 10 to 12 fixtures | 6,000 to 7,200W | 1 x 40A 240V |
| 40ft, cannabis flower, 1,000 PPFD | 14 to 16 fixtures | 8,400 to 9,600W | 1 x 50A 240V |
Dimming a LED to 80 percent increases its PPE by 5 to 8 percent (lower drive current runs the diodes cooler), so photons per dollar of hydro actually improves. The same dimming on HPS cuts spectrum quality and bulb life. That dimming flexibility lets you adapt to bright Ontario February days without overshooting DLI.
What circuit and panel size does the lighting load require?
The circuit and panel a container greenhouse needs depends on total electrical demand, not lighting alone. Ontario container greenhouses run on standard 240V split-phase with 100A, 200A, or in commercial builds 400A at the main panel. Lighting is only one part of total demand: ventilation fans, dehumidifiers, pumps, shoulder-season heaters, possibly CO2, and the controller all add up. Auxiliary on a 40ft leafy-greens build runs 1,500 to 2,500W; tomato pushes 3,000 to 4,500W because heat and humidity management is heavier.
Honest panel-sizing math: leafy greens 5,000 to 6,000W peak (25A at 240V); tomato/pepper 10,000 to 12,000W (50A at 240V); cannabis flower 12,000 to 15,000W (60A at 240V). Present those numbers to your electrician as dedicated container load on top of whatever the residence or shop already draws. Ontario Electrical Safety Authority (ESA) inspection requires a permit for any new sub-panel or dedicated circuit, and the inspector will want to see the load calculation in writing.
The 80 percent continuous-load rule
Canadian Electrical Code requires continuous loads (anything running three hours or more, which includes every grow light photoperiod) to be sized at 125 percent of the calculated load. Stated the other way: you can only put 80 percent of breaker capacity on a continuous load. A 20A breaker covers 16A continuous; a 30A breaker covers 24A; a 40A breaker covers 32A. Run those numbers before you commit to a circuit size. We have seen builds where the operator bought 8,000W of LED on a 30A 240V circuit, which only legally carries 5,760W continuous, and the install had to be torn out before ESA would sign it off.
What does a winter photoperiod cost in Ontario hydro?
The hydro cost of a winter photoperiod tracks your lighting wattage, your photoperiod length, and the time-of-use window you run in. For winter 2026, Ontario time-of-use rates are 9.8 cents per kWh off-peak (7pm to 7am weekdays plus weekends), 15.7 cents mid-peak, and 20.3 cents on-peak. Operators who structure photoperiod into off-peak save 52 percent compared to on-peak. A 16-hour photoperiod from 5pm to 9am sits almost entirely in the off-peak window on weekdays.
A 40ft leafy-greens container at 2,880W on a 16-hour off-peak photoperiod consumes about 46 kWh per day, which works out near 6,900 kWh across a 150-day winter. A 40ft tomato build at 6,500W draws roughly 104 kWh per day, well over double the leafy-greens load. A 40ft cannabis flower at 9,000W climbs to about 144 kWh per day. Running through the morning peak window instead of staying off-peak adds 30 to 60 percent to whatever the off-peak figure would have been.
| Container build | Lighting kW | Daily kWh (16h) | 150-day winter kWh | Running load vs 40ft leafy greens |
|---|---|---|---|---|
| 20ft leafy greens | 1.44 kW | 23 kWh | ~3,450 kWh | 0.5x |
| 40ft leafy greens | 2.88 kW | 46 kWh | ~6,900 kWh | 1.0x (baseline) |
| 40ft herbs | 2.10 kW | 34 kWh | ~5,100 kWh | 0.7x |
| 40ft tomato/pepper | 6.50 kW | 104 kWh | ~15,600 kWh | 2.3x |
| 40ft cannabis flower | 9.00 kW | 144 kWh | ~21,600 kWh | 3.1x |
Those numbers exclude auxiliary load (fans, dehumidification, heaters), typically another 30 to 60 percent. The Ontario Electricity Rebate knocks 23.5 percent off the bill for residential customers under threshold; commercial operators above the rebate pay the full TOU rate. A winter of supplemental lighting for a 40ft tomato container in Ontario is a meaningful hydro line item on its own, and that is before auxiliary load is added on top.
Paul LeBlanc, owner: “Every container greenhouse buyer asks the wattage question first. The hydro bill is the answer most of them are actually after. We will walk through the math with you in the yard before you commit, because the lighting bill is the operating reality you live with for the next ten winters. Better to know what it costs in November before you sign for the bin in May.”
How does photoperiod timing cut the hydro bill?
Photoperiod timing cuts the hydro bill by parking the lighting hours inside off-peak windows, and it is the single biggest saving available, bigger than fixture choice. A 16-hour photoperiod from 5pm to 9am falls 14 hours off-peak and 2 hours mid-peak. The same 16 hours from 6am to 10pm would land 3 hours off-peak, 4 mid-peak, and 9 on-peak, pushing the daily bill up by 52 percent. For our 40ft tomato build, that scheduling choice alone swings the seasonal hydro bill by more than half on the same fixtures, same canopy, same crop yield.
Plants do not care whether light hours are AM or PM as long as they get a consistent dark period. Flowering cannabis runs 12 on / 12 off, scheduled cleanly into 7pm to 7am off-peak.
Off-peak photoperiod patterns that work
- 12-hour (cannabis flower): 7pm to 7am, 100 percent off-peak weekdays.
- 14-hour (tomato/pepper): 6pm to 8am, 13 off-peak, 1 mid-peak.
- 16-hour (leafy greens, herbs): 5pm to 9am, 14 off-peak, 2 mid-peak.
- 18-hour (cannabis veg): 4pm to 10am, 14 off-peak, 4 mid-peak.
Auxiliary equipment does not follow the photoperiod schedule. Schedule heating, dehumidifier runtime, and irrigation pumps into off-peak where possible. Smart controllers like Trolmaster, Argus, and Priva support TOU-aware scheduling and usually pay back in one winter for any container running over 3 kW.
How much heat and humidity do the lights add?
The lights add heat in direct proportion to their wattage, because every watt into a grow light eventually becomes heat. LEDs turn 50 to 60 percent of input into PAR photons; the rest becomes heat. For HPS the share landing in photons is closer to 30 percent, so an HPS array dumps far more warmth into the canopy. If your container is doing double duty as a workshop or office in the off-season, the same steel shell also lends itself to other ways to convert a sea can into usable interior space. In a 40ft container with limited air volume, the heat is a significant management problem.
For our 2,880W LED leafy-greens build, the heat load is 1,200W, four 300W radiant heaters running continuously. In deep winter it offsets heating demand; in summer it needs active ventilation. For our 6,500W tomato build, heat load reaches 3,000W. Sizing exhaust, dehumidifier, and heater requires the heat-mass-balance equation around lighting load. Most Ontario integrators include this in the design package; DIY builds should hire a greenhouse HVAC engineer to validate.
The VPD interaction
Vapour pressure deficit (VPD) links temperature, humidity, and transpiration into a single number. Lighting drives canopy transpiration, raising humidity and dropping VPD. Lighting heat raises ambient temperature, raising VPD. A well-designed controller manages all three variables together. A 40ft container running supplemental LED at full output during a cold dry winter night can hit a comfortable 1.0 to 1.2 kPa VPD for tomato production if ventilation and dehumidification are sized to the lighting heat load.
Which fixtures, drivers, and dimming controls should you choose?
Choosing fixtures, drivers, and dimming controls for a container comes down to form factor, voltage, and dimming protocol. The Ontario commercial market settled on a short list of LED makers: Fluence (Vypr), Heliospectra (MITRA), Gavita (CT 1930e, RS 1900e), P.L. Light (Hortiled), and Chinese OEMs through Canadian distributors at 30 to 50 percent lower capital. Tier 1 fixtures carry five-year warranties and DLC listings, which matter for IESO Save on Energy incentives.
For containers, three selection criteria rise to the top. Low-profile form factor: an 8ft 6in ceiling leaves about 7ft of mounting height after canopy and fixture body, so a 3-inch-deep LED bar fits where a 12-inch HPS does not. 240V input: most commercial grows wire 240V to cut current in half, so fixtures must accept 240V natively. 0-10V dimming: fixtures need to dim when sun pours through translucent panels on bright February afternoons, and 0-10V is the standard controller interface.
Driver placement matters in a container
Some LED fixtures integrate the driver into the housing; others split it into a separate enclosure. For a container greenhouse, split-driver is the smarter choice. Drivers run hotter than the LED diodes. Mounting them outside the high-humidity canopy zone extends driver life by 30 to 50 percent. Integrated-driver fixtures are cheaper upfront but tend to fail first inside the humid canopy environment of a 40ft tomato container.
What are the container install realities for ceiling height and mounting?
The container install realities for ceiling height and mounting are mechanical work the fixture datasheet rarely addresses. An 8ft 6in dry-box ceiling leaves about 12 inches of working clearance above a 6ft canopy, tight for pruning. The 9ft 6in high cube adds an extra foot and is the default for any build above the lettuce tier. Mounting uses uni-strut channel bolted to the container’s roof beam structure. Beams are heavy-gauge steel and accept through-bolts cleanly, but you must know where the beams run and avoid mounting through corrugated sheet alone. Experienced modifiers install the uni-strut before interior cladding goes up; retrofits require popping cladding to find structure.
The Niagara cucumber container build
A Niagara peninsula cucumber operation we delivered a 40ft high cube to in autumn 2025 spec’d 8 commercial LED bars at 600W each, total 4,800W on a 30A 240V dedicated circuit. The container was glazed on the long side facing south, pairing supplemental lighting with passive solar. Photoperiod ran 16 hours from 4pm to 8am, hitting 14 hours off-peak. Winter lighting hydro across 180 days stayed manageable because the bulk of the load sat in the off-peak window. Crop yield through January and February ran 70 percent of summer production, the kind of number Ontario operators target when they make the supplemental lighting investment.
Maintenance access is the last install consideration. LED diodes run 50,000 hours, but drivers fail and dimming controls glitch. For operations running lettuce in summer and tomato in winter on the same container, height-adjustable mounts pay for themselves in canopy uniformity. The wattage and circuit numbers are one half of the build conversation; the physical install plan is the other half, and both halves need to align before fixtures get ordered. If you want the uni-strut, venting, and electrical rough-in done before the box leaves the yard, that is what our at-yard conversion work covers, finished under engineered drawings and ready for your licensed trades to certify on site.
Frequently Asked Questions
How much supplemental lighting does an Ontario container greenhouse need in winter?
Typically 8 to 21 mol per square metre per day of supplemental DLI from October through February to close the 76 percent natural light deficit. Leafy greens sit at the lower end, tomatoes and cannabis at the upper. A 40ft leafy-greens build needs roughly 2,400 to 3,000W of LED on a 16-hour photoperiod.
Is LED or HPS better for a container greenhouse in Ontario?
LED is the honest call for new builds. LED PPE runs 2.7 to 3.0 micromoles per joule versus 1.7 to 2.1 for HPS, which means 40 to 50 percent lower hydro for the same canopy PPFD, plus less radiant heat to manage in a tight ceiling. HPS retrofit makes sense when existing hardware has multiple seasons of life remaining.
What size electrical circuit does a 40ft container greenhouse need?
Leafy greens at 300 PPFD: 20A 240V for 2,880W. Tomato or pepper at 600 PPFD: 40A 240V for 6,000 to 7,200W. Cannabis flower at 1,000 PPFD: 50A 240V for 8,400 to 9,600W. Apply the 80 percent continuous-load rule and pull an ESA permit before energizing.
How much does it cost to run grow lights in an Ontario container greenhouse?
It depends on crop and wattage. A 40ft leafy-greens build at 2,880W on a 16-hour off-peak photoperiod uses about 46 kWh per day, near 6,900 kWh across a 150-day winter. A tomato build at 6,500W roughly doubles that to about 104 kWh per day, and a cannabis flower build at 9,000W climbs to about 144 kWh per day. Multiply your daily kWh by the off-peak rate of 9.8 cents to estimate the lighting hydro, then add 30 to 60 percent for auxiliary equipment.
Can I run supplemental greenhouse lighting on a regular residential panel?
A 100A residential panel usually supports a 20ft leafy-greens container or small 40ft herb build without a sub-panel upgrade if the existing household load leaves 30A of headroom. A 40ft tomato or cannabis container generally requires a 200A panel or dedicated sub-panel. Have an electrician assess capacity before assuming the container will fit.
What is DLI and why does it matter for container greenhouses?
DLI (daily light integral) is the total photosynthetically active photon dose over 24 hours, in mol per square metre per day. Every crop has a target DLI range below which yield drops and above which the crop wastes energy. Ontario container greenhouses run roughly 4 mol of natural DLI in winter, and the supplemental system delivers the gap.
Can I save on hydro by running grow lights only at night in Ontario?
Yes. Ontario time-of-use rates put off-peak (7pm to 7am weekdays, all weekend) at 9.8 cents per kWh versus on-peak 20.3 cents. A 16-hour photoperiod from 5pm to 9am captures 14 hours off-peak and 2 hours mid-peak, cutting the lighting hydro bill by roughly 52 percent compared to running 6am to 10pm.
Does supplemental lighting add too much heat inside a container?
It adds significant heat. A 2,880W LED leafy-greens build adds about 1,200W of heat. A 6,500W tomato build adds 3,000W. In winter that offsets heating demand; in summer the container needs active ventilation. HVAC sizing must account for the lighting load.
What ceiling height do I need for supplemental grow lights in a container?
An 8ft 6in standard container works for leafy greens or herbs with low-profile LED bars and a 5 to 6 foot canopy. A 9ft 6in high cube is the better choice for tomato, pepper, cucumber, or cannabis because the extra foot accommodates higher fixtures and taller crops. Most Ontario builds above the lettuce tier specify high cube.
Can I retrofit supplemental lighting into an existing container greenhouse?
Yes, but retrofit is harder than new-build install. You need to expose roof beam structure, run new conduit, install uni-strut on the beams, and validate the electrical service. Budget 30 to 50 percent more than a fresh install for retrofit labour, expect 5 to 10 days for a competent crew.
Sources
- Agriculture and Agri-Food Canada. (current). Harrow Research and Development Centre, Leamington ON, greenhouse lighting research. agriculture.canada.ca
- Greenhouse Canada. (current). Finding the right light recipe and smart lighting in greenhouse vegetable production. greenhousecanada.com
- MechaTronix. (current). Typical PPFD and DLI values per crop. horti-growlight.com
- Greenhouse Product News. (current). Plant lighting efficiency and efficacy: micromoles per joule. gpnmag.com
- Ontario Energy Board. (2026). Ontario Time-of-Use Electricity Rates Winter 2026. ontario-hydro.com
Reach Van Blanc in Brantford
We have been supplying shipping containers across Ontario since 1995. Our warehouse is at 90 Morton Avenue E in Brantford, and we deliver right across the province on a cash-on-delivery basis. No surprise fees, no chase-the-paperwork.
Van Blanc Ent. Inc., 90 Morton Ave E Unit 1B, Brantford, ON N3R 7J7. +1 888-509-6658
For any container greenhouse build, the lighting plan needs to fit the box before the box gets delivered. Walk our yard, pick the dry-or-high-cube container that matches your crop and aisle plan, and let us run the wattage math with you in person.
Related Reading
Ready to price your container?
Tell us the size and your postal code and we’ll send back an honest, all-in number, container, delivery, and placement, usually within 1-3 days. No pressure, no mystery fees.
Family-run in Brantford since 1995 · 200+ containers in stock · 4.9★ across 124+ Google reviews · every box graded by a person, walk it before it lands.