Older electricity meters used the power flowing into the home to drive round a rotating disk and counted the revolutions to measure consumption.  All modern meters, including smart meters, use solid-state measuring devices which do away with the mechanical rotating disk.

Across the world, different countries have chosen different technologies to communicate data on consumption from the meter to the electricity company, but the vast majority use some form or other of radio communication – sending the information using wireless, or radiofrequency, transmissions.
In Ireland, the meters will use mobile-phone technology, specifically the older and more basic 2G system.  Each smart meter has within it the equivalent of the transmitter and antenna of a mobile phone, and it uses these to send data over a 2G network to ESB Networks.  Each time the meter sends data it is very much like sending a text message or a single short email from a mobile phone.

In the first instance, smart meters will send one message per day containing that day’s consumption to ESB Networks.  This would usually be during the night and would take only a fraction of a second to send – as noted above, in terms of the transmission, it is basically just a text message.
The technology allows the meter and ESB Networks to communicate for other reasons, e.g. to check status or to perform updates.  We don’t plan to use that facility very often if ever, but the technology allows for it.  They would still be very short transmissions, very widely spaced.
In the future, smart meters will allow the electricity supply companies to offer you new products and services.  For example, you could choose to switch to a tariff that varied through the day (more expensive in peak hours than off-peak or at night). More options will emerge as we all explore what smart technology can offer.  These options might involve more frequent transmissions between meter and ESB Networks, though each separate transmission would still be a very short package of data, just like a text message.  And in all those examples, it would be your choice whether to take up the option offered.

Part of the longer-term vision for smart meters does involve the meter communicating within the home.  For instance, you could have a display in the home to tell you about your current consumption, and that would receive data by communicating with the smart meter.  Those communications would usually also be by radiofrequencies, although, as the range required (just within the home, not outside it) would be smaller, the power level of the communications would be very low.
That lies in the future, however.  In the first instance, the smart meters installed by ESB Networks will not have that functionality, they are simply replacements for your existing meter.  And it would be your choice whether to adopt some of those functions and capabilities in future.
One other development is that, in future, smart gas meters send their consumption data to the smart electricity meter, so that the electricity meter can then send both sets of consumption to ESB Networks.  Again, that link between the gas meter and the electricity meter would be short range and therefore low power.