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. You are not usually right next to the meter when it transmits. And the duration of exposure is also low – typically just one short message once a day in the first instance. 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
installing communicate using 2G (or GSM) technology. This can operate at four different specific
frequencies: 850, 900, 1800 and 1900 megahertz (MHz). Those are very similar frequencies 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 either 2 watts or 1 watt (2 W or 1 W) depending on
the frequency. In practice, the power may well be less, but these are the
maximum possible values.
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. The way the technology works, it
is simply not possible for smart meters to produce continuous transmissions.
The exposure limits specify that the
relevant exposure is the exposure averaged over six minutes. With smart meters, even the instantaneous
exposure during a transmission is within the exposure limits. But when you average over the specified six
minutes – which would almost certainly contain just one transmission lasting no
more than a second – the averaged exposure drops still further.
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 communicate just once a day. In future, that could increase, as electricity companies or other
businesses take advantage of the technology to offer you new products and services. But it would still only be a relatively small
number of short individual transmissions widely spaced in time. And it would 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 well to the lower end of
the range of radiofrequency exposures in the home, both because they are not
usually close to the body, and because of how infrequently they actually
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 extracted.
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 being installed in Ireland
use 2G technologies, and therefore the transmissions have the specific 2G
modulations, rather than 3G or 4G.
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.