Those 4K ultra-HD TVs can blast your electric bill

Pining for a 4K ultra-high definition television set this holiday season? Shop wisely, or you could end up getting zapped.

According to a report from the Natural Resources Defense Council (NRDC) and Ecos Research that looked at 2014 and 2015 models, UHD TVs on average consume 30 percent more power than other sets, including HD TVs. That means a bigger electricity bill.

Indeed, if every TV with a screen size of at least 36 inches were suddenly to suck up power at the same rate that the average UHD set does, consumers' electric bills would jump by $1 billion per year, according to the groups. That's roughly three times the total amount of juice households in San Francisco use annually.

Not all UHD sets drink electricity, with products varying wildly in their energy efficiency. Noah Horowitz, director of NRDC's Center for Energy Efficiency, noted that the study found a nearly three-fold difference in energy consumption between different makes of UHD TVs, with some models using barely any more energy than HD sets.

With the total number of TVs in the U.S. exceeding the country's population, by some estimates, sets' energy efficiency amounts to an environmental issue. According to the analysis, new 36-inch and larger TV sets will likely be UHD. At their current average use of electricity, that would add an additional 5 million metric tons of carbon to the atmosphere.

Meanwhile, one-third of all TVs sold are 50-inches or larger, and the largest and least efficient models can use as much electricity in a year as a new refrigerator.

Consumers can take steps to minimize the impact. One is to look for "Energy Star" UHD models that meet government-mandated energy efficiency goals. Another is to enable Automatic Brightness Control on a set, which adjusts screen brightness to match ambient lighting. According to NRDC, that can reduce power consumption by 50 percent.