In short, the postulate states that "energy efficiency improvements that, on the broadest considerations, are economically justified at the microlevel, lead to higher levels of energy consumption at the macrolevel." This idea is a more modern analysis of a phenomenon known as the
Jevons Paradox. In 1865,
William Stanley Jevons observed that England's consumption of coal increased considerably after
James Watt introduced his improvements to the steam engine. Jevons argued that increased efficiency in the use of coal would tend to increase the demand for coal, and would not reduce the rate at which England's deposits of coal were running out. Like Jevons Paradox, the Khazzoom-Brookes Postulate is a deduction that is largely counter-intuitive as an efficiency paradox. When individuals change behavior and begin to use methods and devices that are more energy efficient, there are cases where, on a
macro-economic level, energy usage actually increases." The effect of higher energy prices, either through taxes or producer-induced shortages, initially reduces demand but in the longer term encourages greater energy efficiency. This efficiency response amounts to a partial accommodation of the price rise and thus the reduction in demand is blunted. The end result is a new balance between
supply and demand at a higher level of supply and consumption than if there had been no efficiency response." or, rather, that improvements in energy efficiency were associated with increased energy usage. Many of the increases that can be seen from empirical data might as well have taken place without efficiency gains, possibly leading to even larger increases. Further important considerations are the potentials and limits of the efficiency multiplier effect, considering efficiency as a kind of
complex system learning process. At the beginning of the
learning curve efficiency and productivity improvements get physically easier to achieve and then later improvement slows as the difficulty of learning increases and the practically achievable level of efficiencies is reached. In market systems the investor choices may be driven by physical benefits or financial ones independently, so they may conflict. Promoting efficiencies that accelerate the depletion of resource necessities may raise their monetary value by increasing scarcity. This may lead in succession to decreasing physical returns on
energy returned on energy invested. Accelerating toward terminal limits of resource utility is a form of
tragedy of the commons following the equivalent of a maximum rate of depletion rather than a maximum longevity or utility principle. The rebound effect will usually be larger if energy costs make up a large share of the total costs of a given product or its consumption, and will also depend on demand elasticities. For example, fuel efficiency of cars will lead to increased mileage to a larger extent than visits to restaurants would be increased by a better energy efficiency at restaurants (e.g. for cooking, fridges, heating): Energy costs make up a smaller amount of total costs for restaurants and will therefore influence their prices to a smaller extent, and thus also not the number of visits to restaurants. ==Publications== • • • • ==See also==