Energy efficiency ratings on televisions are flawed and likely to mislead consumers, a US environment advocacy group has claimed.
The Natural Resources Defense Council NRDC said many sets were designed to perform well in government tests, but used more energy in regular use.
It said energy consumption could be twice the expected amount.
But the US Consumer Technology Association CTA said modern TVs were an "efficiency success story".
The NRDC said it found many television sets disabled energy saving features with little or no warning when a viewer adjusted other settings, such as the picture brightness.
It also found that a test video produced by the US Department of Energy to determine energy consumption typically used less energy than real-world television broadcasts.