Smart meters use one or more RF transceiver in the 900MHz, 1.8GHz or 2.4GHz band. During transmission (normally limited to a maximum of 50% of the time and in practice usually very much less than this), they radiate RF power. RF radiation causes heating of body tissue. International standards for maximum personal exposure (MPE) for members of the general public, based on reducing the heating effect to 1/50th of the amount shown to cause noticeable effects in laboratory animals, are in force and must be complied with. In NZ the current standard is NZS2772:Part 1: 1999, which is to all intents and purposes identical to other national and international standards. Smart meters using the 900MHz and 2.4GHz ISM bands must comply with the RF radiation power limits of the NZ SRD GURL (in order to limit interference). In practice they radiate much less power than this allowance and then for only a small fraction of the time, but even if they radiate the maximum amount, on both bands simultaneously, all the time, and the worst case additive reflection occurs, at any distance greater than 1m from the meter, the exposure is less than 35% of the allowable limit. This leaves at least 65% of the MPE limit for radiation from all other sources.
Smart meters using the 900MHz or 1.8GHz (or potentially the 2.1GHz) cellular bands transmit using the GPRS network used by mobile phones. They transmit data similar to SMS texts, at the same RF radiation levels as a mobile phone. Because under normal conditions they are much further away from the body than a mobile phone, they result in much lower exposure. Even if the meter spends half its time transmitting data, in a marginal coverage area, at full power, and the worst case additive reflection occurs, at any distance greater than 1m from the meter, the exposure is less than 28% of the allowable limit. This leaves at least 72% of the MPE limit for radiation from all other sources. Taking the advice from NZS2772 to “minimize unnecessary or incidental RF exposure”, a sensible approach is to locate Smart Meters such that the general public are unlikely to spend longer than a few minutes per day at a distance of less than 1m from them. This will ensure that mobile phone use remains, by far, the highest RF exposure source that any individual is likely to be exposed to.