A well-lit workshop isn't about watts. It's about lumens per square meter: 300 to 400 lumens per m² for a garage where you do DIY, 500 to 750 for a workshop where you work every day, 750 to 1,000 for detailing or painting.
For a 30 m² garage used seriously, this represents approximately 15,000 to 20,000 total lumens. This is the figure to compare between two kits — not the wattage.
Why watts no longer mean anything
In the days of fluorescent tubes, a 58 W tube illuminated like a 58 W tube: power was a reliable benchmark. With LEDs, two 40 W panels can produce 3,200 lumens for one, and 5,600 for the other. Everything depends on the quality of the diodes and the efficiency of the power supply.
Watts measure what you pay to the electricity company. Lumens measure what you see. Only the latter tells you if you'll see the head of a screw deep inside the engine.
The relationship between the two has a name: luminous efficacy, in lumens per watt. Below 100 lm/W, the product is outdated. Between 110 and 140 lm/W, the equipment is decent to good.
The real needs table
| Usage | Lumens per m² | For 20 m² | For 30 m² | For 50 m² |
|---|---|---|---|---|
| Storage garage | 150 to 200 | 4,000 lm | 6,000 lm | 10,000 lm |
| DIY garage | 300 to 400 | 7,000 lm | 10,500 lm | 17,500 lm |
| Mechanical workshop | 500 to 750 | 12,500 lm | 19,000 lm | 31,000 lm |
| Detailing, painting | 750 to 1,000 | 17,500 lm | 26,000 lm | 44,000 lm |
Three pitfalls in product sheets
- "Chip" lumens. Some manufacturers advertise the raw flux of the diodes, before the diffuser. What actually comes out of the panel is 10 to 20% lower.
- Total lumens of the kit. A kit of six panels advertising 30,000 lumens means 5,000 per panel: check that the calculation is accurate.
- The number alone, without the surface area. 20,000 lumens in 20 m² is comfortable. The same 20,000 lumens in 60 m² is dim.
Ceiling height: the forgotten factor
Light intensity decreases with distance. A 4 m ceiling does not return the same light to the floor as a 2.50 m ceiling. The rule we apply: beyond 3 m, add 50% more panels, or accept a lower illuminance level at floor level.
What about uniformity?
Two installations can display the same total lumens and be completely different in use. Four large spotlights concentrate light in four spots and leave the rest in shadow. A hexagonal grid distributes the same amount of light over the entire surface.
Without an instrument, one test is enough: place yourself in four different spots in the room, bend down as if you were working, and see if your own shadow bothers you. If so, it's not a question of lumens, it's a question of distribution.
Key takeaways
- Think in lumens per m², never in watts.
- 300 to 400 lm/m² for DIY, 500 to 750 for work, 750 to 1,000 for detailing.
- Beyond 3 m ceiling height, +50%.
- The total is not enough: distribution matters as much as quantity.
To convert these lumens into the number of panels, see white hexagonal LED kits.
