Jevons Paradox
William Stanley Jevons, 1865, in The Coal Question: “It is wholly a confusion of ideas to suppose that the economical use of fuel is equivalent to diminished consumption. The very contrary is the truth.”
Jevons observed that James Watt’s steam engine was vastly more efficient than Thomas Newcomen’s earlier design. Less coal per unit of work. Intuition says: less coal consumed overall.
The opposite happened. By 1900, British coal consumption had tripled.
The mechanism: efficiency lowers the cost of using a resource per unit. Lower cost increases demand. If demand increases faster than efficiency gains, total consumption rises.
Watt’s engine didn’t just reduce coal per application — it made coal-powered machines economical for industries that couldn’t afford them before. Mining, manufacturing, transportation. More applications meant more total coal consumption.
This is rebound. Some rebound is small — a more fuel-efficient car might lead to slightly more driving. The Jevons paradox occurs when rebound exceeds 100% — when total consumption increases despite efficiency gains.
Modern examples:
LED lighting: LEDs use a fraction of incandescent energy. Response: we installed vastly more lights. Illuminated billboards, decorative lighting, screens everywhere. Global lighting energy consumption continues to rise.
Air conditioning: Each unit is more efficient than ever. Response: we air-condition more spaces. Office buildings that were designed for natural ventilation get retrofitted with A/C. Total cooling energy rises.
Data storage: Cost per gigabyte has fallen exponentially. Response: we store more data. Every click, every photo, every transaction. Total storage energy rises.
Computing: Compute per watt improves constantly. Response: we compute more. AI training runs now consume the power output of small cities.
Efficiency gains are good. The paradox reveals that efficiency alone fails to solve resource constraints when demand is elastic. Making something cheaper makes people want more of it.
If the goal is reduced consumption, efficiency must be paired with limits on total use — caps, pricing, allocation. Efficiency without constraint is acceleration with a better engine.
Go Deeper
Books
- The Coal Question by William Stanley Jevons (1865) — The original. Available free online. Surprisingly readable.
- The Efficiency Paradox by Edward Tenner — Modern treatment of how efficiency gains create unexpected consequences.
- The Jevons Paradox and the Myth of Resource Efficiency Improvements edited by John M. Polimeni et al. — Academic collection on rebound effects.
Essays
- Amory Lovins’s responses to Jevons — Lovins argues that with proper policy, efficiency can reduce total consumption. The debate continues.
- “The Rebound Effect: An Assessment of the Evidence” — Various economic meta-analyses estimate rebound at 10-60% for most efficiency improvements.
Related: [[feedback-loops]], [[carrying-capacity]], [[systems]]