Traditional domestic meters simply record cumulative kWh totals and have no facility to record consumption against a specific period.  Even two-rate meters, such as used with Economy 7 tariffs, simply record cumulative totals during the on-peak and off-peak periods respectively.

The UK has recently implemented a standard known as P81, which permits the use of NHH metering for export as well as import, avoiding the high cost of recording, analysing and "settling" kWh for each of the 17520 HH periods each year.

NHH meters suitable for recording import/export include the Iskramaeco product which can also provide a pulsed output for use with remote AMR (Automated Meter Reading) systems.

In order to correlate the consumption of domestic consumers using NHH meters, it is necessary to apply "settlement profiles".  These make statistical  assumptions based on historical load research and, in many instances bear no relation to the actual consumption of any given household.

Currently, the assumed profile for export comprises two "chunks", one two hour period in the early morning and another for five hours in the evening.  Although it is recognised that this is a crude assumption, it is considered accurate enough for the very small number of systems currently in operation.  In the meantime, a number of monitoring projects are attempting to record and understand export profiles as well the modified import profile for micro-generation homes.

BEAMA project

HH (Half Hourly) meters are used in commercial installations where the significant amounts of kWh exported in each half hour period, justifies the cost of such metering and the underlying settlement process.

In many cases these are provided with AMR functionality to facilitate readings and minimise errors.

These are available from numerous manufacturers but are not included here as the related infrastructure is not currently considered suitable for micro CHP.

HH metering will be essential to capture the true value of a specific microgeneration installation; this will allow consumption to be accurately attributed to the relevant cost period and hence optimise the value of each customer.  However, in order to implement VPP solutions, it will be necessary to do this in real time in response to centralised cost message information.

For many years, the cost and effectiveness of manually reading meters has been under scrutiny. There are clear advantages to being able to remotely access meters, including accurate start/end reads with change of tenancy and change of supply and to avoid the need to estimate readings when access to the property cannot be obtained.

However, within the current UK market, the structure of the industry acts as a disincentive to the implementation of advanced metering.  The meters are owned by the metering company which charges a daily rental to the energy supplier.  If a customer changes supplier (which can in theory take place every 28 days!), the new supplier may not wish to pay the higher rental for an advanced meter, particularly if they do not support the related infrastructure.  The meter company then has a stranded asset with no means of recovering the investment.

Regardless of this, meters are being developed which can provide a higher level of service.  Indeed, some meters are being developed which provide the functionality not only to remotely read meters, but also to communicate additional information, such as load constraints or CRM.

Fundamental to the control and metering of domestic consumers with micro CHP (or any other form of generation) is the ability to receive and in some cases send information.

A number of options for communication within the home are being considered including:

1) PLC (Power Line Carrier) which attaches a carrier signal to  the mains cabling and hence has connectivity to all electrical appliances without the need for additional wiring.  This is probably the simplest and cheapest system, perfectly adequate for the bandwidth required for load management.

2) LAN

3) Wireless

From the home to the central control, the options include:

1) PLC up to a sub-station from whence the data is transferred to radio. This has the disadvantage of requiring high penetration levels to achieve economies of cale and although successful in countries with monopolistic (Italy, France) or mandated (Sweden) common infrastructure, is unsuitable for the UK.

2) GSM and GPRS allow the implementation of incremental capacity, but currently suffer from very high operational costs, although there is no reason that the structure of charges could not be changed to reflect the low bandwidth and use of off-peak communication network capacity.

3) Fixed (telephone) using PSTN or broadband.