With millions of smart meters projected to be installed, opponents have raised concerns over the health impact from the radios inside these two-way meters.

Industry group the Electric Power Research Institute today released the results of tests that show the radio frequency emissions of one smart meter fall well below the federal safety threshold. It measured the radio frequency energy coming from commonly used Itron smart meters, part of a few tests it's doing in response to public health concerns.

Testing Itron meters for RF signals.

In some places, such as Northern California, there is fierce opposition to smart meters because of concerns around privacy or health. The rollout of smart meters has inflamed worries over people's sensitivity to radio frequency signals from items such as cell phones and Wi-Fi routers.

Though there is ongoing study on the effect of cell phone signals on people, smart meters are relatively new and have not been researched as much.

Smart meters are equipped with a radio to send data from a meter to a utility on regular intervals. Meters can act as part of a mesh network, sending collected data from a neighborhood to a central point. With a greater amount of real-time data, utilities can more quickly locate outages and use energy more efficiently by closely gauging demand. Consumers, too, can get more insight on when and how they use energy.

In practice, meters are not on continuously but instead transmit data in quick bursts several times an hour, averaging about a minute and a half of transmission time per hour, according to EPRI.

EPRI's measurements of RF signals from in front and behind a smart meter found them well below the Federal Communications Commission's safety limits. The strength of the signal dropped with distance. Because smart meters transmit for only a small fraction of the day, the RF level in actual usage would be less than 1 percent of the FCC limit, EPRI said.

Echoing other analyses, EPRI also published a chart showing that other smart meter RF emissions fall below those from cell phones, cell phone base towers, microwave ovens, Wi-Fi routers.