What this tool does
Shows how lamp wattage and height change estimated lux on the tray using a fixed formula.
Compares the reading to crop-specific lux bands from the plant database or a microgreen default band.
Estimates monthly electricity cost from wattage, a 16 h/day schedule, and your tariff.
How it works
- Lux estimate: lux = (watts × 500) / (d²) with d = height_cm / 20. At 0 W, lux is 0.
- Monthly cost (EUR/USD/THB): (watts ÷ 1000) × 16 h/day × 30 days × price per kWh.
- Status bands use classifyTrayLux in cropLightLux.ts: compare lux to luxMin/luxMax, dimBelow, and burnAbove derived from the crop band or DEFAULT_TRAY_LUX_BAND (8000–12000 lux target, dim below ~3000, burn above ~20000 for defaults).
Assumptions and default values
| Default EUR tariff | €0.32/kWh (Flanders residential avg. label) |
|---|---|
| Default USD tariff | $0.16/kWh (EIA US average label) |
| Default THB tariff | ฿3.95/kWh (MEA 2026 residential label) |
| Cost photoperiod | 16 h/day, 30 days/month |
| Wattage / height sliders | 0–100 W, 10–100 cm |
| Default starting UI | 40 W, 30 cm height, EUR |
Worked example
Computed with the same functions as the live tool.
Inputs
| Wattage | 40 W |
|---|---|
| Lamp height | 30 cm |
| Tariff | €0.32/kWh |
Outputs
| Estimated lux | 8889 lux |
|---|---|
| Monthly cost | €6.14 |
Limitations
- Lux is modeled, not measured — no substitute for a calibrated lux or PAR meter at your bench.
- Single-point inverse-square-style formula; multi-bar layout uses a separate canopy visual (LedCanopySimulator) without changing the main lux formula.
- Crop lux bands depend on plant JSON completeness.
FAQ
How much light do microgreens need?
On this site, the default tray band when no crop is selected is about 8,000–12,000 lux on the tray surface. With a crop selected, targets come from that plant's light JSON (lux min/max for a growth stage). The simulator classifies your reading as too dim, in range, high, or burn risk against those bands.
How is lux calculated from LED wattage and height?
The tool uses lux ≈ (watts × 500) / (d²) where d = lamp height in cm ÷ 20. That is a simplified inverse-square-style estimate, not a substitute for a PAR meter.
Why does monthly cost use 16 hours per day?
Electricity cost on the tool uses a fixed 16 h/day × 30 days/month multiplier with your kWh tariff, independent of crop photoperiod settings elsewhere.
What tariff is the default?
EUR mode defaults to €0.32/kWh (Flanders residential average label in code). USD and THB defaults are also defined in the Light Simulator page.
When does the tool warn about heat?
Heat risk is flagged when wattage is above 40 W and lamp height is below 20 cm (boolean in code, separate from lux burn classification).