The exposures that smart meters produce
Electric and magnetic fields (EMFs) come in two sorts – mains frequency and radiofrequency. Smart meters actually produce lower mains-frequency EMFs than traditional meters. When it comes to radiofrequency EMFs, the exposures are very low, for several reasons. The power of the transmission is low. And you are not usually right next to the meter when it transmits. The FAQs below give more detail on the safe exposure levels produced by smart meters.
What frequencies do smart meters transmit at?
The smart meters that ESB
Networks are currently installing communicate using 2G (or GSM)
technology. This operates at a narrow band of frequencies at 900
megahertz (MHz), very similar to many other wireless technologies.
What determines the exposure from a smart meter?
The exposure a person gets to
radiofrequencies from a smart meter depends on three factors: the power of the
transmission, the distance away from it they are, and the duration of
exposure. We consider each of these in
the following questions.
What is the power of the transmissions?
Like the mobile phones whose
communications technology smart meters borrow, smart meters are designed to
transmit with as low a power as possible. The 2G technology used is
capped at 2 watts (2 W).
This is the maximum possible
value. In practice, it is usually rather
less, because the technology reduces the power level automatically to the
lowest level actually needed to maintain communications.
How does the exposure change with distance from the smart meter?
Like any other sort of transmission, the level
of exposure reduces with distance away from the smart meter. Except for very close to the meter, it falls
away with what is called an “inverse square” variation, which is really very
rapid. It means that each time you
double the distance, the exposure falls by a factor of four.
Mobile phones are designed to be safe (to
produce exposures that are below the safety limits) even when used close to the
head, just a centimetre or two away. So
smart meters are also safe, even if you managed to get similarly close to them
when they were transmitting. But of
course, you would normally not be close to a smart meter. You would typically be a metre or more away,
and at that distance, the exposure levels have fallen many-fold, typically a
factor of 20 or more.
What is the duration of exposure?
Each time the smart meter needs
to communicate data to ESB Networks, it does so as a single short package of
data, very much like a single text message or a single short email. Each
such transmission lasts less than a second. However, between these
communications, the smart meter still maintains contact with the base
station. The level of power needed to
maintain this link is automatically reduced to a minimum.
Overall, what is the exposure?
Radiofrequency exposure is measured in two
different ways. When a person is quite
close to the source, the Specific
Absorption Rate (SAR) is measured, and when they are further away, power
density is measured.
If you put your head right against the
smart meter, it would probably produce an SAR of around 0.5-1.5 W/kg, depending
on the exact orientation. At say 1 metre
away, it would probably produce a power density of around 0.2 W/m2. Both of these values comply with the relevant
exposure limits, as explained in more detail below.
Will the number of transmissions increase over time?
As explained above, in the first
instance, smart meters are expected to send data (meter readings and status
reports) several times a day. In future, that could increase, as
electricity supply companies or other businesses take advantage of the technology to
offer you new products and services. It will be your choice whether to
take up any of these new options that might be offered.
What exposures would communication in the home produce?
In future, as smart technologies develop,
there may be communications within the home.
For instance, you may have an in-home display of your consumption, or
smart appliances that can communicate direct with the meter.
These communications would also be
wireless. Because the range required is
less – limited to inside the home, rather than having to communicate to base
stations outside the home – the power would be less. It’s quite likely they would use an existing
protocol, such as Zigbee. To take that
example, Zigbee is limited to 1/8 W, so a power 16 times lower even than the
maximum power the smart meter can use to transmit outside the home. The
exposures also would be correspondingly lower.
At this stage the smart meters being installed
will not be capable of communicating within the home.
How do these exposures compare with other wireless technologies?
There are numerous sources of
radiofrequency exposures in everyday life: mobile phones, Bluetooth, Wi-Fi,
DECT phones, baby monitors, etc, plus, of course, all the broadcast TV and
radio that has been around for a lot longer.
The highest exposures come from sources that you use close to your body. The most obvious example is using a mobile phone against the head to make a
voice call, though even that still complies with the exposure limits.
Other sources produce lower exposures, either because they are lower power
(e.g. Wi-Fi, bluetooth) or because you do not use them so close to the body.
Smart meters are to the lower end of the range of radiofrequency exposures in
the home, mainly because they are not usually close to the body.
Does the particular way the data are transmitted make a difference?
All wireless technologies,
including smart meters, work by encoding the data onto what is called a
radiofrequency “carrier wave”. They do that by modulating the carrier
wave. It is the carrier wave that carries the signal between the sender
and the receiver, and it is the modulation that allows the data to be sent and
Each wireless technology tends to use a fairly similar carrier frequency, but
the details of the modulation vary a lot. 2G then 3G and 4G each
developed different and better modulation patterns to be able to send more
data, and similarly for other wireless technologies like Wi-Fi. The smart
meters currently being installed in Ireland use 2G technologies, and therefore
the transmissions have the specific 2G modulations, rather than 3G or 4G. Smart
meters installed in future phases of the rollout could use different
technologies with different specific frequencies and modulations.
However, the exposure limits don’t distinguish between different modulation
patterns, they simply limit the overall exposure. That is because there
is no good scientific evidence that living cells or tissues are able to
distinguish the different types of modulation used by different technologies.
What matters is simply the overall exposure, and with smart meters, that
overall exposure complies with the exposure limits.
Do smart meters also produce mains-frequency exposures?
Yes, they do, like any other appliance or
piece of equipment that uses mains electricity. But smart meters actually
produce much smaller mains-frequency magnetic fields than the traditional
rotating-disk meters they are replacing do. Both types of meter produce exposures that are comfortably within the
exposure limits, but the smart meter does so by a much larger margin.