Smart Charging Explained


GreenFlux help  GreenFlux App  Charger Communications

What is Smart Charging?

In the Electric Nation Project Smart Charging means slowing down or pausing EV charging for short periods of time to keep the additional load from EV charging within the existing capacity of the electricity network and avoid costly and disruptive upgrades.

Smart Charging may have other meanings, including controlling EV charging to take advantage of renewable energy generation or time of use tariffs (such as Economy 7) – Electric Nation is not trialing these approaches at this time.

Why is Smart Charging needed?

The electricity distribution network (substations and cables) that bring electricity into all our homes has a finite capacity: These networks are designed to supply electricity to our homes when we use the most electricity – usually this is during the late afternoon and early evening on cold winter days.

Each distribution network is unique, they vary by age and by how much extra loading (e.g.  homes, schools, shops and businesses) has been added to them since they were originally installed.  This means that their ability to cope with any additional electrical load, such as EV charging, varies too.

If these distribution networks are overloaded they get hot and may wear out sooner than planned.  Worn out networks tend to fail more frequently and ultimately may need replacing.  Failures may result in loss of electrical supply for short periods until a fault is fixed.

Electric Vehicle (EV) charging at home is a load that electricity networks were never designed to cope with – a  EV charging can increase a home’s electricity power demand by up to 8 times the normal average!  For an individual home this is usually acceptable and within the capacity of the supply to the home.

But, for the distribution network serving a road/neighbourhood, as more and more EVs are charged at home, this extra load can overload the network at peak electricity demand periods (i.e. winter early evenings).

Smart charging can be used to moderate the EV charging to ensure overall load on a local network is kept within the network capacity to avoid overloading and overheating the network. Smart charging systems, like the GreenFlux system, are designed to avoid, where possible, impacting on your ability to achieve an adequate charge for your EV.

You can watch an explanation of smart charging from Western Power Distribution (your local DNO) on the Electric Nation website here.

What’s the alternative to Smart Charging?

Without Smart Charging, the electricity Distribution Network Operators, the companies who own and operate these networks, have only one option when faced with an overloaded network: that is to replace part or all of the network with new, larger capacity substations and cables (this is called reinforcement in the industry).

For household electricity supplies, the costs of replacing these networks is shared across all electricity customers’ bills – people both with and without an EV.

The more tangible impact of reinforcement is the disruption that these works incur – replacing cables involves digging up roads, gardens and driveways to lay new cables into every property on a network.  This often takes many months and can cause much inconvenience and delay to road users, residents and pedestrians.

Smart Charging may enable Distribution Network Operators to avoid or delay the need to reinforce some networks – if it is cost effective to do so and acceptable to EV owners who want to charge at home.  This is what Electric Nation is investigating, through the trial you are participating in.

How does Smart Charging Work?

The Electric Nation project is using Smart Chargers.  These can communicate with a Smart Charging System (such as GreenFlux who is providing Smart Charging services to the Electric Nation project), when a charger is being used and how much electrical current (power) is being drawn by the EV.

When the overall load of a group of smart chargers exceeds the electricity network capacity the GreenFlux system then commands some of the chargers in the group to reduce the power they are drawing – the “Smart” of the charger enables this to happen.

When will Smart Charging happen?

Smart Charging only happens when the total EV charging load is more than the available capacity on a network, after all other loads, such as electricity used in our homes, shops, offices, etc, are considered.

Usually this in the late afternoon and early evening, most often on winter weekdays, when household electricity demand is at its highest and at the time when many people come home from work and plug their EVs in to charge.

Smart Charging may happen at other times, when a large number of EVs are plugged in and charging at the same time.

How will Smart Charging affect me?

This depends on whether you plug-in your EV to charge when so many other EVs are charging that the electricity network capacity is exceeded .

Here are some examples, the height of the coloured block in the graphs is an indication of the power drawn by a charging EV.

1. You have a PHEV that charges at 3.5 kW (16 Amps) and plug in to charge at 13:00, your car needs a charge for 3¼ hours, by 16:15 your battery is full. Few other EVs are plugged in and there is plenty of capacity on the network for charging EVs: Smart Charging is active, but no action is taken because the network capacity limit is not exceeded. There is no difference in the time it takes to charge your EV whether Smart Charging is active or not:

2. You have a 3.5 kW (16 Amps) charging EV and plug in to charge at 15:30, your car needs a charge for 6¾ hours, so by 22:15 your battery should be full.  This is equal to about 24 kWh, or roughly 80 miles of range.  If Smart Charging is active and a Smart Charging event occurs that evening between 17:30 and 19:45, your charging may well be managed, in the example below charging is paused 3 times for a ¼ hour each time:

These pauses mean the EV has to remain charging until 23:00 to attain a full charge, to make up for the earlier ¼ hour pauses.Unless you were planning to make a journey at 22:15, that required a full battery, this is likely to be of little concern to you, as most people leave their car charging overnight for use the next morning.

3. You have a faster 7 kW (32 Amps) charging EV and plug in to charge at 17:00, your car needs 7 ½ hours to reach full charge (i.e. will be charged at half past midnight, 00:30).
If a Smart Charging event occurs that evening between 17:30 and 19:45, your charging may well be managed, in the example below charging is reduced to half power twice (for two ¼ hour periods) and paused three times (for ¼ hour each time):

These pauses mean the EV has to remain charging until 01:45 to attain a full charge, to make up for the earlier Smart Charging actions.

Unless you were planning to make a journey in the middle of the night, this is likely to be of little concern to you, as most people leave their car charging overnight for use the next morning.

4. You have a faster 7 kW (32 Amps) charging EV and plug in to charge at 19:30, your car needs 5 hours to reach full charge (i.e. will be charged at 01:30).Most smart charging events will be over by the time you plug in.  So, there’s no effect on the charging, your car will be charged by 01:30:

There is no difference.

5. You use Economy 7 to charge your EV and have a faster 7 kW (32 Amps) charging EV. You plug in at 17:00 and set timer to start charge at Midnight 00:00, your car needs 6 ½  hours to reach full charge (i.e. will be charged at 06:30). Smart charging events are highly unlikely at the time your car starts charging (midnight). So, there’s no effect on the charging, your car will be fully charged at 06:30:

There is no difference.


How does Smart Charging affect a group of EVs?

Smart Charging only takes action when the combined electricity load of all EVs charging at any one time exceeds the capacity of the local electricity network they are supplied by.

Smart Charging events are all unique and depend on the time of day (how much electricity is used in homes) and how many EVS are plugged in and charging at that time.

Smart charging can occur at any time if a large number of EVs are charging.

The graph below is an example of a real Smart Charging event – an especially busy EV charging evening in this case.

The Green Line is the available network capacity after all other loads (that is power used in homes, offices, shops, other businesses, etc) are added up and compared to the capacity of the network

Each of the coloured blocks is an EV on charge

Before about 4:30 PM the EV charging load is much less than the available capacity – no smart charging action is applied.

At around 4:30PM the available network capacity drops, primarily because of rising home electricity use, the Smart Charging system steps in and starts to reduce the power being drawn by some chargers, the GreenFlux system reviews the situation every 15 minutes and reallocates the available power to different chargers every 15 minutes, in a sort of “round robin”, so that no one charger is penalised more than another.

As the network capacity continues to fall, the Smart Charging system restricts more charging events, pausing some chargers if required.

It’s difficult to see, but during this time, more EVs arrive at homes and are plugged in to charger – these too are included in the Smart Charging event “round robin”.

You can just about see how some coloured blocks reduce in size (charging rate reduced) or disappear for one ¼ hour and then reappear (charging paused) in this Smart Charging period.  No car is paused for more than ¼ hour, unless it has completed charging.

Just after 6:00 pm the spare network capacity (green line) gradually starts to rise as home energy usage starts to fall, charging restrictions are maintained, but are gradually reduced.  However, through this period more cars arrive at home and are plugged in to charge, so the Smart Charging event continues until 9:30 pm in this case.  When network capacity rises above the total EV charging demand (all EVs charging at their full rate) the Smart Charging event is over and all EVs continue charging to completion in the late evening and overnight.

Is Smart Charging the same every day?

No, when Smart Charging happens and how much charging management is required depends on how many EVs are charging at any particular time.

The more EVs that are charging in any ¼ hour period the more likely Smart Charging is required to protect the electricity network.

The amount of Smart Charging action required also depends on the number of EVs charging, generally speaking the more EVs that are charging, the more action is required and the longer the Smart Charging event will last. The amount of restriction your EV experiences depends entirely on how many other EVs are charging at the same time as your EV is charging.

Can I avoid Smart Charging?

The GreenFlux Smart Charging system actively monitors chargers in the Electric Nation trial all of the time and takes action when EV charging loads exceeds the electricity network capacity – this can happen at any time, but is more likely at some times of day than others.

Electric Nation have recognised that Smart Charging events can be an inconvenience when a driver needs an immediate charge to make a journey  (say later in an evening after returning from work) – GreenFlux have developed a Smart Charging App, which enables you to request high priority for your charging session.  This App is currently being tested and will be made available to all trial volunteers shortly  – click here to find out more.

Can’t I just unplug the charger communications to stop Smart Charging?

If you unplug the communications equipment for your charger then the charger will go into Smart Charging Safe Mode – this restricts your charging to a maximum of 13 Amps, just less than the standard 3.5 kW (16 Amps) charging rate for PHEVs and less than half for 7 kW (32 Amps) charging rate used for most battery EVs.

If you find your charger is restricted to 13A charging – check your charger communications equipment is plugged in and working – click here to learn more.

This Safe Mode is designed to protect the electricity network, if everyone were able to charge at full rate, then on busy networks with lots of EVs there is a higher chance of network failure and subsequently nobody getting their EV charged until the network fault is fixed.

Collaboration Partners

Sign up for regular email updates