Size the LED supply and cables.

Use the combination that can actually be on.

Add the power of sections that can operate simultaneously. For RGBW, do not automatically assume every colour always runs at 100%, but do not apply diversity factors without a software or design rule that guarantees them.

I [A] = P [W] / V [V]

Add controller and accessory consumption, then choose a supply with margin consistent with temperature, ventilation and the manufacturer's derating curve. A nominal rating equal to the load is not automatically a robust design.

At equal power, 24 V halves current.

Voltage must still match the load. Never drive a 12 V strip at 24 V, and do not expect the same brightness from a 24 V load supplied at 12 V.

Calculate outgoing and return conductors.

Vdrop = I × Rconductor

Resistance depends on material, cross-section, total length and temperature. A five-metre physical run uses roughly ten electrical metres across positive and return. Check both percentage drop and the minimum voltage reaching the load in the worst case.

For long strips, power injection at multiple points can reduce brightness gradients, but each branch needs consistent polarity, cross-section and protection. Do not create accidental parallel return paths through controllers or data signals.

Protect the cable, not only the supply.

• Size fuse or protection to conductor capacity and expected current.
• Check ambient temperature, bundling and installation method.
• Maintain appropriate separation and protection on the mains side.
• Check torque, ferrules and terminal current ratings.
• Have fixed wiring installed by qualified personnel under applicable rules.