How many watts per foot does a high power LED strip use, and how hot does it get?
A high power LED strip on a wide board draws 16-45 W/m, which is roughly 5-14 watts per foot, so a full 5 m reel can exceed 200 W — size the driver with 20% headroom and feed it from both ends or mid-strip. Heat is handled mechanically: the wide copper plane spreads it along the board, and above about 20 W/m the strip must sit in an aluminium profile with full-length contact, in free air, or lumen maintenance suffers long before the warranty ends.
Electrical sizing
Compute the load from watts per metre times run length, then add 20% so the driver is not sitting at 100% duty. At 45 W/m and 24V a single metre already draws 1.9 A, so a 5 m run pushes more than 9 A through the copper — far beyond what one end-feed can carry without visible drop. Both-ends feeding halves the effective distance; a mid-strip tap does the same and is fully supported on DENO's per-segment constant-current boards.
Where a run must stay dead flat over 10–15 m, move up to 48V. The same wattage draws a quarter of the current of a 12V build, which is the single largest lever available on voltage drop.
Thermal rules that actually matter
Every 10 °C of unnecessary junction temperature costs measurable lumen maintenance over the life of the installation. The mitigation is mechanical, not electrical:
- Always mount above ~20 W/m in an aluminium profile with full-length contact
- Use 2–3 oz copper so heat spreads along the board rather than pooling under each die
- Leave the profile in free air — sealed plaster voids trap the heat you just spread
- Derate one drive step for IP67/IP68 builds, where the potting adds thermal resistance
Industry references and standards
- Energy & compliance — EU Regulation 2019/2020 (ErP for Light Sources) — Efficacy, flicker (Pst LM) and SVM limits that apply to strips sold in the EU.
- Energy & compliance — ENERGY STAR Lighting Program — North American efficacy and lumen-maintenance benchmarks.
- Engineering standards — IEC 62717 — LED Modules for General Lighting — Performance and lumen-maintenance requirements for LED modules.
More wide PCB answers
- What are the brightest LED strip lights you can actually buy?
- How many lumens per metre and per foot does a high lumen LED strip give?
- Are super bright LED strip lights available in 12V, or do you need 24V?
- Are the brightest LED strip lights available waterproof for outdoor use?
- Is a double row LED strip brighter than a high density single row?
- Can I get custom width bright white LED strip lights made?