Right now, sitting wherever you are, doing nothing much, your body is generating roughly 100 watts of continuous power. That is the same output as an old incandescent light bulb — the kind that heated a room as much as it lit one.
You are, at this moment, a biological power plant running at the same wattage as a household light fitting. And you have been since you woke up.
The maths is simple. An average adult burns about 2,000 calories a day just by being alive — breathing, pumping blood, digesting, thinking, maintaining body temperature. Convert those calories into watts: 2,000 kilocalories × 4,184 joules per kilocalorie ÷ 86,400 seconds in a day = 96.9 watts. Call it a hundred.
What makes this strange is where the power goes. Your brain uses about 20 watts — roughly 20% of your total resting energy — despite making up only 2% of your body weight. Twenty watts is enough to run a dim LED bulb. That is the power budget for consciousness, memory, language, vision, and every decision you have ever made.
The liver and spleen together take another large chunk. The heart runs on roughly 1 to 5 watts depending on demand. The rest is distributed across organs, muscles, and the constant background hum of cellular maintenance.
For comparison, here is your body's output against some familiar devices:
- Human sprinting: 2,000+ watts (briefly)
- Olympic cyclist (sustained): ~400 watts
- Human walking: 300–400 watts
- Human at rest: ~100 watts
- Laptop computer: 50–100 watts
- Brain alone: ~20 watts
- LED light bulb: ~10 watts
- Smartphone charging: ~5 watts
Start exercising and the numbers climb. Walking lifts you to 300–400 watts. A Tour de France cyclist sustains roughly 400 watts for hours. Sprinting can briefly push past 2,000 watts.
But here is the kicker: your body is only about 20–25% efficient at turning food energy into useful mechanical work. The other 75–80% is released as heat. That is why crowded rooms feel warm. Fifty people standing together produce roughly 5,000 watts of thermal energy — the equivalent of a large space heater, running constantly, powered by sandwiches.
You are not sitting still right now. You are running a hundred-watt biological engine that has been on since the day you were born, fuelled by everything you have ever eaten, and radiating enough heat to warm a small room — while somehow also being conscious.