Load Control through Smart Meters

Smart meters offer a number of ways to control and monitor loads in the home. This capability is sometimes called Demand Side Response or DSR. There are three basic methods of load control, the customer themselves acting on a signal, using the meter itself to switch the load or, to use the HAN (Home Area Network) to switch a load remotely.

Why do we need to involve the Smart Meter in this process? The Smart Meter holds the tariff information and therefore is one of the key information sources in understanding when and how the load should be managed. It also records the amount of load reduced or increased under this control mechanism at half-hourly intervals to match the way electricity is priced in the wholesale market.

These load control features are an optional part of the SMETS specification meaning that suppliers do not have to offer them to customers. If offered it is the customer's choice whether to use these services or not.

Currently, only suppliers can use this functionality with the customer's permission, other parties such as DNOs (Distribution Network Operators) cannot use it. This is because the customer needs to give permission and understand the benefits and costs; only the suppliers are in a position to have this interaction with customers. Therefore, it is likely that any load control for the electricity system will be through services offered by suppliers using their customer base.

Customer advantages
  • Save money
  • Earn money
  • Reduce emissions
  • Control appliances.
Industry advantages
  • Balance supply and demand
  • Improve security of supply
  • Reduce expenditure on generation
  • Help to integrate renewable energy
  • Reduce expenditure on new distribution networks or the reinforcement of existing networks.

Customer acts on signal

Monthly Report on number of Electricity Meters installed by type

This is the simplest, requiring just a message to the customer saying that they should reduce or increase load if they want to. The customer would already have agreed a contract showing the payment or price for the service they are providing. Here a Smart Meter is only needed to record the level of customer participation in changing their load.

Auxiliary load control switch

Monthly Report on number of Electricity Meters installed by type

Smart meters with 5 terminals have an auxiliary load control switch (ALCS) within the meter itself which can be used to switch a second electrical circuit off and on. The switching pattern can be set via:

  1. A calendar in the meter providing the schedule, or
  2. The supplier sending ad hoc commands as required.
The first option above is very like the Economy 7 meters used to control storage heaters today.
The second option here would allow the supplier to act in case of a system emergency, for example when wind generation is suddenly higher or lower than expected.

In both cases the customer has to agree to the overall process before the supplier can use it.

HAN Connected Auxiliary load control switch

Monthly Report on number of Electricity Meters installed by type

Smart meters can also control circuits by sending on and off commands across the HAN thus removing the need for a circuit to be wired back to the meter. This method of control is known as HCALCS. Through this method up to 5 devices can be controlled independently (one of these could be the hardwired ALCS circuit mentioned above).

Electric car charging is a good example of how this could be used.

Smart Vehicle Charging

New smart meter-enabled tariffs can reward consumers that charge their electric vehicles (EVs) during off-peak times, such as at night, by passing through savings from using energy at lower price periods.

When combined with smart chargers consumers can automate this process, not only making it easier to shift charging to cheaper periods but also increasing the responsiveness of their vehicle to real time signals such as excess renewable generation or local grid constraints.

New two-way smart chargers can even enable vehicles to act as mini power stations, supplying energy back to the grid or even directly to consumers' home. Given that cars spend over 90% of their time parked, this opens up significant new capacity that would otherwise be wasted. Electric vehicles can also help optimise onsite generation such as solar by providing a battery bank to use surplus green and free energy that would otherwise be exported to the grid.

What is smart charging?

Smart Charging is when the charging cycle can be altered by external events, and the EV effectively integrates with the whole power system in a grid.

This means that, when permitted by the user, the charging of an EV can be paused or the rate of charge increased or decreased in response to commands received from energy network operators. A key feature of smart charging is that the user remains in ultimate control, setting the parameters to suit their needs while allowing some level of autonomy in return for lower energy costs.

Ultimately, smart charging will allow the user to specify when they require their vehicle (e.g. by 8:00am) and the system will provide the optimal charging profile to deliver the lowest cost while ensuring the vehicle is ready when needed. At times of low demand, the system may charge immediately in one time block or at other times may charge in a series of time blocks in response to fluctuating demand, local network pressure and availability of renewable power but will always meet the specified needs of the user.

Proportional Load Control

The load control methods above have a serious limitation in that they can only switch a load on or off, ideally it would be useful to control some loads proportionally, for example to reduce to charging rate on an electric vehicle to half power.

This capability is being added to version 5 of the SMETS 2 specification.

The new capability will be called the Auxiliary Proportional Controller (APC) and can be used in two ways:

  • APC functionality that can be used in the same way ALCS
  • HAN-connected Standalone Auxiliary Proportional Controller (SAPC) functionality that will connect to the HAN via the Communications Hub.

(Page updated: 2021-05-03)

Questions & Answers

Are SMETS2 meters compatible with storage heaters?
Yes. A fifth meter output is required to control the storage radiator load - 5 terminal meters are now available from most suppliers. (Updated: 2021-02-12)

Can my supply be turned off remotely?
Smart meters have the facility to remotely disconnect and reconnect both the electricity and gas supply. However, most suppliers seem to have decided it is too dangerous to remotely disconnect or reconnect, as in the case of disconnection they cannot always be sure that the customer isn't relying on a supply for serious health reasons and in the case of reconnection the customer may have left a cooker on for example. (Updated: 2015-01-23)

I just bought a house with solar panels. What do I do?
First, you need to check if the previous owners were signed up for FIT (Feed In Tariff). If they were, you'll need to check who the FIT provider is and complete a 'Change of ownership' form. You could then switch to another provider if you wished.
If the solar panels haven't been registered for FIT, then you can only get SEG (Smart Export Guarantee) payments. (Updated: 2021-04-21)

Do SMETS2 meters support solar panels?
Yes all SMETS2 meters support solar panels as this was included in the SMETS2 specification. However, this does not mean your suppliers will support it. A lot of work is required in a supplier's back office systems to set up the meter correctly, and process and store the messages required to operate export properly.
We suggest you check with your own supplier whether they can support export yet. (Updated: 2021-02-12)

How does the smart meter record energy generation if a solar panel is installed?
All smart meters will record the export and import separately, and you will be able to see the readings by stepping through them on the meter display. All the meters should show all 4 power quadrants. You can ignore the reactive ones and just look at active import and export.

Power quadrants:
  • Active energy import (Wh) - this is what we are billed for normally
  • Reactive energy import (varh)
  • Active energy export (Wh) - this is your useful export power
  • Reactive energy export (varh).
The bad news is that many companies have not set up their systems to automatically collect or use the export information, as it would have taken time and money they don't have for such a low volume user base. (Updated: 2018-10-02)

What is a HAN-connected auxiliary load control switch (HCALCS)?
Similar to an ALCS (Auxiliary load control switch), a HCALCS allows large domestic loads, such as electric vehicles chargers, to be controlled independently of the main power supply. However, rather than being integrated with the meter directly, the switch is remotely connected via the Home Area Network. This provides more flexibility, avoiding the need for new wiring back to the meter when a new load is connected.
Although we have seen some initial projects start using HCALCS, none seem to have reached mass production yet. (Updated: 2022-01-16)

What is an Auxiliary load control switch (ALCS)?
Large domestic loads like storage heaters or heat pumps can be connected and controlled independently of the customer's main supply. An ALCS inside a smart meter can switch the electricity supply to the devices connected to it on or off based on an agreed switching pattern. It works in the same way as traditional Economy 7 meters, providing a scheduled period of power to connected devices. Subject to an agreement made between supplier and customer this could also support ad hoc commands allowing switches to respond to wider network conditions such as periods of excess renewable generation. (Updated: 2021-04-09)

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