How Motor Efficiency Losses Show Up as Heat

No motor converts 100% of electrical energy into motion — the rest goes somewhere, and that somewhere is heat.

Every real motor loses some fraction of input electrical energy to resistive heating in its windings, magnetic losses in its core, and friction — commonly landing somewhere in the 80-95% efficiency range for good modern designs under favorable conditions, with the remainder converted directly to heat.

Why efficiency drops at extremes

Motors are typically most efficient somewhere in the middle of their operating range; running at very low speed with high torque (common when a robot is holding a static pose against gravity) or right at the edge of peak torque tends to push efficiency down and heat generation up.

The downstream effect

Because that lost energy becomes heat right at the joint, motor efficiency isn't purely an energy-consumption question — it's directly tied to how much cooling capacity a joint needs and how long it can sustain high-torque operation before thermal limits force a derate.