Physics: Why LED Efficiency Exceeds Incandescent Bulbs

Energy efficiency measures how much of the energy we put into a system actually does the job we want, expressed as the ratio of useful output to total input: Efficiency = (Useful Power Output ÷ Total Power Input) × 100%. Every device transforms energy, and some of it inevitably escapes as waste — usually heat. The higher the efficiency, the smaller that waste, and the greater the share of input converted into the desired output. This matters because efficiency shapes everything from household bills to national energy demand. Consider lighting: incandescent bulbs rely on a heated filament, losing most input energy as thermal radiation, while LEDs use electroluminescence, where electrons recombine across a semiconductor junction to emit photons directly, bypassing those losses. Comparing a bulb's useful light output against its electrical input reveals how effectively each technology converts energy — and why large-scale adoption in places like hospitals can cut costs, ease grid demand, and reduce carbon emissions.