Smart meters represent one component of the advanced metering infrastructure (AMI). Although data to and from smart meters may be transmitted through wired connections, many smart meters make use of miniature, low power radio transceivers to wirelessly communicate with the electric utility and with the Home Area Network (HAN) that provides home owners with the ability to interact with electrical appliances and systems within the home. Deployment of smart meters has raised concerns by members of the public about possible adverse health effects that could be related to exposure to the radiofrequency (RF) emissions of the meters. As part of on-going efforts to address public concerns on this issue, this report documents the collection of information on RF exposure related to the operation of two particular models of Smart Meters produced by Itron Inc.
This report is focused on the RF aspects of smart meters and in particular, the strength of the transmitted RF fields that may be produced by the meters from a human exposure perspective. The greatest difficulty in arriving in determining realistic time-averaged exposure from smart meters is associated with determining transmitter duty cycles since the meters only emit RF radiation for very brief periods at intervals that are not necessarily periodic.
The project team conducted laboratory and field measurements of the RF emissions of Itron smart meters. One objective was to determine realistic estimates of the operational duty cycle of meter transmitters. The team also investigated the effectiveness of metal meshes and stucco walls in shielding smart meters.
The smart meters studied in this report are currently being deployed by two electric utilities in California. The meters are part of wireless mesh networks consisting of approximately 500 to 750 “end point meters”; for each of these networks, one meter is configured as a collector point referred to as a “cell relay” by Itron. The cell relay collects data from the various end point meters and conveys these data onto the cellular wireless wide area network (WWAN) for communication back to the electric utility company’s data management system. Mesh network communication among the many meters is provided by a 900 MHz band transceiver RF LAN (local area network). A HAN feature is supported by a 2.4 GHz transceiver.
Data collection was carried out in a laboratory setting and at residences and in neighborhoods in southern California and Colville, Washington, supplemented with theoretical modeling studies. The results indicate that RF fields from the investigated smart meters are well below the maximum permitted exposure (MPE) established by the Federal Communications Commission (FCC) for the general public. For instance, at one foot, the time-averaged RF field from an end point meter would be expected to not exceed 0.8% of the MPE) established by the (FCC). For the cell relay, the RF field would not exceed 0.2% of the MPE. Even at very close distances, such as one foot directly in front of the meter, with an unrealistic assumption that the transmitters operate at 100% duty cycle, the resulting exposure is less than the FCC MPE. When viewed in the context of a more typical, realistic exposure distance of 10 feet, the RF fields are much smaller, about 0.008% for the end point meter and about 0.002% of MPE for the cell relay. For occupants of a home equipped with a Smart Meter, interior RF fields would be expected to be at least ten times less intense simply due to the directional properties of the meter. When the attenuation afforded by a stucco home’s construction is included, a realistic value of the interior RF field would be about 0.023% of the MPE for an end point meter and about 0.065% for a cell relay. Regardless of duty cycle values for end point and cell relay meters, typical exposures that result from the operation of smart meters are very low and comply with scientifically based human exposure limits by a wide margin.
Application, Value and Use
This report documents an investigation of the characteristics of RF fields associated with Itron Smart Meters. The project was undertaken to improve understanding of public exposure to the RF emissions produced by smart meters and to respond to public concerns about potential health effects.
Measuring electric energy consumption with so-called smart meters in residential and commercial environments is becoming more commonplace as part of the development of Advanced Metering Infrastructure (AMI) in the electric utility industry. With the deployment of smart meters, public concern was raised about potential health effects associated with RF emissions from smart meters EPRI is responding to these concerns with research efforts to provide objective information on RF emissions related to smart meters.