How to Choose LED Driver Wattage (and Why 20% Headroom)
Size an LED driver to the total load wattage plus 20% headroom. Worked examples for strips, light boxes and track runs, plus derating rules for sealed spaces.
Towe Engineering · Published November 2, 2026 · 3 min read
Choose LED driver wattage by adding up the wattage of everything on the output and multiplying by 1.2: an 8 m run of 10 W/m strip needs an 80 × 1.2 = 96 W driver, so a 100 W unit is correct. The 20% headroom exists because drivers at exactly rated power run hotter, and heat is what ages the electrolytic capacitors that determine driver lifetime. In fully sealed enclosures with no metal contact, derate by a further 20%.
Key points
- Driver wattage = total load W × 1.2
- Sealed, unventilated enclosure → derate another 20%
- 24 V halves the current of 12 V, cutting voltage drop on long runs
- 100% aged drivers (like Towe's) protect the headroom you paid for
The formula
Driver wattage = total connected load × 1.2
The 20% headroom keeps the driver out of its thermal ceiling. Inside a driver, electrolytic capacitors age roughly twice as fast for every 10 °C of extra core temperature — so a driver running permanently at 100% rated load in a warm ceiling can lose years of service life compared to the same driver carrying 80%.
Worked examples
| Installation | Load calculation | Driver to order |
|---|---|---|
| 8 m of 24 V strip at 10 W/m | 80 W × 1.2 = 96 W | 100 W (TF series) |
| Light box with 6 × 15 W modules | 90 W × 1.2 = 108 W | 120 W (TB ultra-thin) |
| 8 track spots × 12 W | 96 W × 1.2 = 115 W | 120–150 W (48 V track) |
| Facade floodlights, 6 × 150 W | 900 W × 1.2 = 1080 W | TD 1000–1200 W IP67 |
Derating rules that override the formula
- Fully sealed, no metal contact: derate another 20%. The aluminium housing needs something to conduct into; a driver floating in foam or wood has nowhere to put its heat.
- Hot climates at full sun: for Gulf and South-Asian facades, specify the SiC-based TY series, which holds full rated power at high ambient with low temperature rise.
- Long cable runs: voltage drop steals drive voltage from the far end. On 24 V runs above ~10 m, inject power at both ends or step up to a heavier cable gauge.
Why wattage claims need auditing
“300 W” on a datasheet is a claim, not a measurement. Towe verifies every model at true full rated power before it enters the catalog — 100% of production also runs full-load aging on 10 racks, so the rating you buy is the rating you get. When comparing suppliers, ask one question: is the rating true at 40 °C ambient, full load, after aging?
Quick reference: Towe ranges by wattage
| Power | Indoor series | Outdoor IP67 |
|---|---|---|
| 7–100 W | TC linear, TT universal | TH compact |
| 100–400 W | TF, TN, TB, TZ, TG smart | TD, TY, TF-Fang |
| 400–600 W | CB premium | TD, TY, FY, TF-Fang |
| 600–2000 W | — | TD, TY, FY |
This article describes general manufacturing practice for machined and fabricated components. It is not a substitute for a drawing-specific engineering review — tolerances, material selection and process capability depend on the individual part.