Why cheaper energy can mean more energy use
Efficiency reduces the resources needed for each unit of work. But it can also make that work cheaper, changing how much people want to do. A steam engine that burns less coal to produce a given amount of power lowers the cost of running machinery. Businesses may then run equipment longer, install more engines, or use steam for tasks that were previously too expensive.
The key comparison is between two effects: the fuel saved each time an engine runs and the extra fuel burned because engines are used more often or in more places. If the added use is large enough, total coal consumption rises even though each engine is more economical.
A rebound, not a contradiction
Economists call the direct increase in use after an efficiency improvement a rebound effect. It does not mean the technology failed: each unit of output still takes less fuel. It means efficiency changes the price of using that output, and lower costs can prompt people to consume more of it.
The effect can extend beyond the original machine. Cheaper steam power can make a wider range of production profitable, encouraging investment in factories and equipment that also need fuel. In that case, the efficiency gain helps expand the activity around the engine, not just its hours of operation.
What efficiency alone cannot tell us
A more efficient machine does not automatically increase total resource use. The outcome depends on how strongly demand responds to the lower cost, and how much new activity becomes worthwhile. If use barely changes, efficiency mainly cuts consumption; if use expands sharply, some or all of the savings can be eaten away.
That is why a fuel-saving design cannot be judged only by what it burns per hour. The larger question is how much cheaper power changes what people build, produce, and run.
