Grow lights for a narrow 24-inch shelf
A 4-foot bar overhangs a 24 inch shelf by about 2 feet. Two-foot bars fit it exactly.
| Shelf (length x depth) | 2 ft bars | Total at 10 W each | 1020 trays that fit |
|---|---|---|---|
| 24 x 12 in | 1 (1 row x 1) | 10 W | 1 |
| 24 x 18 in | 2 (2 rows x 1) | 20 W | 1 |
| 24 x 24 in | 2 (2 rows x 1) | 20 W | 2 |
| 36 x 12 in | 2 (1 row x 2) | 20 W | 1 |
From the calculator, with one row of lights per 12 inches of depth. This is our planning rule, not a standard. Use the watts on the fixture you buy.
Notes
- A short shelf wastes a long bar. Two 2-foot bars link end to end to make 4 feet if you later move to a longer shelf.
- Oklahoma State says tube ends lose about 3 inches of intensity, so keep trays toward the middle of the bar.
- A 24 inch shelf holds one 1020 tray lengthwise at 21 inches, which is why only one or two trays appear in the table for shallow depths.
- See the 4-foot shelf page for longer shelves.
Sources
- Oklahoma State University Extension: Lighting can be tricky when starting seeds indoors (January 2024)
- University of Saskatchewan: Indoor garden, Little Green Thumbs style
- Barrina: T5 20W LED grow light 4FT 5000K (ML20), manufacturer page