LED high bay lighting for warehouses and factories: how many watts do you need?

Step 1: the lux level the area needs

EN 12464-1 (lighting of indoor work places) gives maintained illuminance values per task. As typical guidance from that standard:

The project specification or the client's standard may ask for more. Use the value for the task, not one figure for the whole building.

Step 2: lumens with the lumen method

The lumen method gives the total light the fittings must deliver:

Lumens needed ≈ lux × area (m²) ÷ (utilisation factor × maintenance factor)

The utilisation factor is the share of lamp light that reaches the working plane; it depends on the room shape, the reflectances and the optics, and comes from the maker's photometric data. The maintenance factor allows for lumen depreciation and dirt over time. Example, with assumed values: a 1,000 m² store at 150 lx, utilisation 0.6 and maintenance 0.8 needs about 150 × 1,000 ÷ 0.48 ≈ 312,500 lm, so about 16 fittings of 20,000 lm. For a final layout, ask for a lighting calculation with the actual fitting's photometric file.

Step 3: efficacy (lm/W) decides the watts

Divide the lumens per fitting by its efficacy to get the watts. Compare the luminaire efficacy in the data sheet (lumens out of the complete fitting per watt drawn, driver included), not the chip figure, which is always higher. A more efficient fitting gives the same light with fewer watts and less heat under the roof.

Step 4: beam angle by mounting height

As a rule of thumb, lower ceilings (around 6 to 8 m) use wide beams, about 90 to 120°, so the light overlaps between fittings. Higher mountings (10 m and above) use narrower beams, about 60°, to put the light on the floor instead of the walls. Narrow aisles between high racks are better served by aisle or linear optics. Spacing should follow the maker's spacing-to-height ratio for the optic.

Glare, IP rating and heat

• Glare (UGR): EN 12464-1 sets a glare limit per task, for example UGR 25 for storage and 22 for general industrial work. Forklift drivers look up at racks, so diffusers or recessed optics help.
• IP rating: IP65 is the usual choice for dusty or humid warehouses and factories, and for areas that are washed down.
• Heat: air under a metal roof in a Saudi summer is much hotter than at floor level. Check the fitting's rated ambient temperature (Ta) and the driver's rating against the real conditions; heat shortens driver life.

Replacing metal halide

When you replace metal halide or sodium high bays, compare delivered lumens, not lamp watts: LED fittings reach full light instantly, lose less light to the reflector and use far less power for the same lux. Our metal halide to LED tool suggests the equivalent LED wattage. Check that the existing supply cable and mounting suit the new fitting, and remove the old ballast and ignitor if you only change the lamp with a retrofit.

What to send us for a quotation

The area dimensions, mounting height, the activity (storage, racking, production), the lux target if you have one, the number and wattage of existing fittings, and whether dust, humidity or wash-down is present. With that we offer a fitting, beam angle and quantity, and can quote the cable and accessories on the same offer.

Common questions

This guide is general information. Final selection must follow the project design, the applicable standards and the maker's data.