RF exposure from a smart meter well below FCC limit, study finds


Dr Rob Kavet,
Senior Technical
Executive, EPRI
Palo Alto, CA, U.S.A. — (METERING.COM) — February 23, 2011 – The radio frequency (RF) exposure levels from one type of smart meter, even at close range, fall substantially below the protective limits set by the Federal Communications Commission (FCC) for the general public, according to a new study from the Electric Power Research Institute (EPRI).

The study involved an Itron smart meter, and found that for a continuously operating rack of 10 meters, each operating at a nominal power rating of 250 mW (typical of many residential units), the RF power density level 1 foot in front of the rack was 8 percent of the FCC limit. At distances of 20 and 50 feet these values dropped to 0.18 percent and 0.11 percent respectively. From 8 inches behind the rack, the RF power density was 0.6 percent of the FCC limit.

The study, which was conducted at the manufacturer’s test facility, was intended to serve as a first step in characterizing RF exposures associated with smart meter technology.

“RF is a ubiquitous and increasing presence in our daily lives as evidenced by the expanding use of cell phones and other wireless technologies,” commented Dr Rob Kavet, senior technical executive at EPRI. “Smart meters are integral technology to a modern smart grid, but consumers need to be assured that health issues associated with RF exposures from new technologies have been carefully examined and are well understood.”

For a valid RF field characterization with the meters continuously transmitting, it was necessary to conduct the measurements under defined conditions. This contrasts with the real world, in which smart meters transmit on an unpredictable schedule for very brief periods throughout the day, consisting of individual transmissions milliseconds long in duration.

The Itron products are currently being deployed by Southern California Edison (SCE) and San Diego Gas and Electric Company (SDG&E).

From an analysis of transmissions for almost 47,000 of these smart meters in southern California, which was also included in the study, an estimated 99.5 percent were operating at a duty cycle of about 0.22 percent or less – a value that translates to 3 minutes and 10 seconds of transmitting over a day. The maximum duty cycle associated with any meter did not exceed 5 percent. Further, in a further sample of 6,800 meters in the same area, the reported duty cycles were even lower, with no one-day average duty cycle exceeding 1 percent.

The study report states that the average exposure levels from smart meters, as measured in the study, are at levels similar to those that are present from other common RF sources, both indoor and outdoor. However, as there may be differences in power levels, duty cycles, and other configurations between smart meters and AMI systems, EPRI plans to evaluate other types of smart meters and systems, as well, and also reevaluate exposure patterns as the currently existing systems evolve.