Can better energy efficiency help us reduce our consumption of fossil fuels and curb our greenhouse gas emissions? Maybe not as much as some hope.

While some people tout better and more energy-efficient technology as one solution to our current fuel and climate challenges, their expectations might be overblown. A new study from the UK Energy Research Centre, for example, finds that improved efficiency sometimes creates a tendency to use more energy, or to engage in other activities that counteract the efficiency gains. It’s called the “rebound effect,” and it can work either directly or indirectly to reduce expected energy savings from improved efficiency.

Rebounds occur, for example, when someone who buys a more fuel-efficient car decides to take the occasional longer day trip because, “Hey, I’m not spending as much on gas anymore.” They can also happen when someone who’s improved his home insulation uses the money saved on heating and cooling to pay for a plane trip to Orlando.

Then there’s “backfire,” also known, somewhat bizarrely, as the Khazzoon-Brookes postulate. That’s the even worse effect that can occur when a new energy-efficient technology actually causes overall energy use to increase. It happened, for instance, after the steam engine came onto the scene. Nineteenth-Century Scotland saw its total coal consumption increase tenfold thanks to the steam engine, which made it possible to mine coal at a lower cost, which made it cheaper to produce iron, when then lowered the cost of steam engines and drove the development of the railway industry.

While backfires are uncommon, rebounds are not. A recent report from the InterAcademy Council noted that technology improvements over the past 20 years have helped drive a small decline in the world’s energy intensity — which compares energy consumption to economic output — but not in its overall energy consumption. And the United National Environmental Programme’s latest “Global Environmental Outlook” (GEO-4) warns that, while technology can help defend against environmental stresses, it’s sometimes important to look beyond the “technology-centred development paradigm.”

The UK rebound report concludes we could be overestimating our savings from improved effiency by anywhere from 10 to 50-plus percent. It adds that policy-makers need to start taking rebounds into effect now if they want to enact energy- and carbon-reducing measures that actually work.