Before you install your first DG system, you’ll have one or more simple import meters on your meter board that measure the electricity consumed within your premises in units of kilowatt-hours (kWh) – commonly, 1 kWh is referred to simply as 1 “unit” of electricity.  Most premises have a single import meter but, depending on the electricity price option chosen, you might have more than one.  For example, in some areas a second meter separately measures the electricity that is used by your hot water storage cylinder and the retailer provides a lower price for this electricity and in return retains the right to switch this supply off for a limited number of hours daily.

The vast majority of simple import meters installed today in NZ have a single energy register that you can see as a tumbler dial on the front of the meter or as a series of radial dials for each digit.  Typical examples are shown below.

These meters are read manually by a meter reader on a monthly or, most commonly, a two-monthly read cycle.  Retailers typically bill you monthly and therefore make an estimate of your consumption in the off-read months that is settled out when an actual read is subsequently carried out.

Once you’ve installed DG at your premise, you’ll need more than a simple import metering system as your needs are now slightly more complex.  With DG installed, regulations¹ require you to provide a metering installation that separately measures the quantities of electricity that flow (a) from the network (import) and (b) back into the network (export).  We call this type of metering system import/export metering.  A later section in this document deals with net-metering and net-billing.

While there are quite a few meter manufacturer/model options, they will likely have a more modern appearance and typically incorporate a simple LCD display, such as this one:

An import/export meter will have two separate energy registers that can be read manually by a meter reader.  An alternative is to install two simple meters, one wired to read imported electricity only and the other to read exported electricity.  The exact arrangement used is determined by the metering services company and is possibly influenced by the age of your existing meter and the availability of space for mounting meters on your meter board.

Increasingly commonly in NZ from 2008, manually read meters are being phased out and replaced by so called smart meters, also known as advanced metering systems (AMS).  AMS uniquely and importantly has a two way communications capability – e.g. via the mobile/cellular or lane line telephone network.  This provides the ability to remotely read the meter, upgrade the meter’s internal programming on the fly and measure and log energy use in much shorter time intervals than the usual two-monthly reads by walk-around meter readers.  The most likely time interval to use will be a half hour period, as this fits in with the way that energy is traded in the wholesale electricity market in NZ.

Importantly for DG, an AMS can also be set up in an import/export configuration.