How Much Energy Do Tier 2 Advanced Power Strips Save?

Posted by Mark Stroub on May 3, 2018

Research shows that most U.S. households own an average of four digital devices, including TVs, computers, tablets and smartphones. These devices are often plugged in 24/7, even when they're not in use. According to ENERGY STAR® data, this vampire energy suck can increase a household's overall electric usage by as much as 10 percent.


In an effort to combat this energy loss, electric utilities are encouraging customers to use advanced power strips (APS). But how much energy do APS units really save? A recent white paper examines the data on the energy savings associated with the two most common brands of Tier 2 APS devices: Embertec and TrickleStar.

Why APS savings are so hard to study

It's difficult to quantify the energy savings from APS units because they aren't inherently energy-efficient. Rather, they create efficiencies for other energy users. Thus, they're dependent on how many and what types of devices are plugged into the strips, how often those devices are used, and what they're used for.

For example, a TV could be used to watch satellite or broadcast shows, or play games with a console-all of which affect energy usage differently. Someone may binge watch Netflix one week and then watch only one program the next week, making it difficult to establish a usage parameter.

Some short-term studies have evaluated Tier 2 APS energy savings through a pre-test/post-test experimental design that compares baseline energy measurements with energy measurements during the study period.

A 2012 Northeast Energy Efficiency Partnership (NEEP) analysis of several of these types of studies, along with simulated-savings studies and laboratory testing, found that Embertec and TrickleStar Tier 2 APS energy savings varied from 79 to 386 kilowatts per year, or 22 to 53 percent of annual energy savings.

In 2014, TrickleStar hired UL Environment (ULE) to conduct an environmental claims verification of the energy savings for the company's Tier 2 APS. ULE used lab tests to show that the device saved between 79 and 333 kilowatts per year, or 20 to 47 percent annual energy savings.

Field tests reveal discrepancies

A 2016 PG&E study conducted throughout California is considered the best field test of Tier 2 APS devices to date. The study evaluated residential audio/visual use of Tier 2 APS and found a savings between 110 and 214 kilowatts per year, or 25 to 50 percent of annual energy savings.

But there are concerns because the study relied on both the pre-test/post-test method and a log mode evaluation (LME) method that simulates electricity savings. With the LME approach, the APS system does not actually control the equipment, but instead turns on LEDs that indicate the system may be controlling the APS to reduce electricity loads-for instance, when a user clicks on a TV remote. The savings are calculated based on the time the equipment operates after the LEDs turn on.

"The simulation/LME method avoids the potential issues related to the operation changes between the pre and post periods. However, it creates its own, more serious, issues because the equipment is not actually controlled, and so the [real-world] human reaction is not properly represented," the white paper states.

While a "gold standard" testing method has yet to be determined, one thing is clear: tier 2 APS units are a good investment. Most recent studies show they can result in 20 to 50 percent annual residential energy savings.

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