"Not only do today's large UHD televisions consume almost one-third more energy, on average, than the high-definition (HD) TVs they'll replace, there is a huge range in the efficiency of the UHD models on the market," said senior scientist Noah Horowitz, director of NRDC's Center for Energy Efficiency.

"We found an almost three-fold difference in energy consumption between the best and worst UHD TVs, with some models using little or no more energy than their HD predecessors, proving the technology already exists to cut needless energy waste in these large televisions," Horowitz said.

NRDC's report is the first to analyze the energy use of televisions known as ultra-high definition due to their superior picture quality with 8 million or more pixels. These televisions are sometimes referred to as 4K TVS because the images are about 4,000 pixels wide, and have four times as many pixels as an HD television.

NRDC and its partner, Ecos Research, analyzed public databases of UHD television energy use and market share sales data, and also performed power use measurements on 21 televisions representing a cross-section of 2014 and 2015 models. The testing focused on 55-inch TVs because they are the most prevalent size and represent the best value among UHD televisions on the market today.

In addition. NRDC also pointed that the new High Dynamic Range, or HDR, feature that provides brighter colors and deeper shadows could significantly increase national TV energy consumption. Our testing showed the HDR version of a movie used 47 percent more power than the same title in 4K format. More attention is needed to understand HDR energy use and reduce it.

The report is not all bad news for UHD TV buyers as it lists steps that can be taken to reduce the power drain of UHD televisions. For exsample, nnabling Automatic Brightness Control, which adjusts screen brightness in response to changes in room light levels, caused televisions to use 50 percent less power, on average.

Consumers can cut several hundred dollars off the lifetime energy costs of a new UHD TV by a) buying models with the ENERGY STAR label, b) ensuring Automatic Brightness Control is enabled, and c) avoiding the quick start feature on Internet-connected televisions that results in significant amounts of wasted standby power.

"The national energy and environmental consequences of the transition to UHD TV will be profound unless the TV manufacturing industry devotes sufficient time and resources to improve the efficiency of the TVs brought to market," Horowitz said.

"The good news is that there are steps consumers, manufacturers, and policymakers can take to make sure our newest-generation televisions are not needlessly wasting energy."