Your electricity supply can only provide a certain amount of power at one time. For many small businesses this is rarely a problem, but larger equipment, electric heating or EV chargers can increase the amount of capacity you need.
Understanding your supply capacity can help you avoid problems when your business grows or changes.
What Is Supply Capacity?
Supply capacity is the amount of electrical power your premises can draw from the network.
It is not the same as the amount of electricity you use over a month or year.
Your energy use is measured in kilowatt-hours (kWh), while supply capacity is usually measured in kilovolt-amperes (kVA).
A simple way to think about it is:
kWh tells you how much electricity you use.
kVA helps describe how much electrical load your supply can handle at one time.
What Is kVA?
kVA stands for kilovolt-amperes.
It is a measure of electrical power used when sizing supplies and equipment.
For a small business, you may rarely need to think about it. However, it becomes more important when a site has larger machinery, motors, commercial heating, air conditioning or several EV chargers.
The higher the electrical load at the same time, the more capacity the site may need.
kW and kVA
You may also see kilowatts (kW).
kW measures the useful or active power being used, while kVA measures apparent power. The two figures can be different because some electrical equipment does not use power perfectly efficiently from the network’s point of view.
For many business owners, there is no need to calculate this themselves.
If you are planning a large new electrical load, an electrician or electrical engineer can work out what the site is likely to need.
What Is Maximum Demand?
Maximum demand is the highest level of electricity your business draws at a particular time.
This matters because several pieces of equipment may operate together.
For example, a site might be running:
- heating
- air conditioning
- machinery
- refrigeration
- lighting
- computers
- EV chargers
Each item may be manageable on its own, but the combined demand can be much higher.
So, when checking capacity, it is important to think about what could be running at the same time.
Your Agreed Capacity
Larger business supplies may have an agreed maximum level of power that can be taken from the network.
You may see terms such as:
Maximum Import Capacity (MIC)
or
Agreed Import Capacity (AIC)
These describe the agreed limit for the connection.
The exact terminology can vary, but the principle is simple: there is an agreed amount of power available to the site.
Do All Businesses Need to Know This?
No.
A small shop or office using normal lighting, computers and small appliances may never need to think about supply capacity.
However, it becomes more important when a business uses large electrical loads or plans a major change.
Examples include:
- commercial kitchens
- factories
- workshops
- warehouses
- large refrigeration systems
- electric heating
- heat pumps
- data equipment
- EV charging
If your electrical needs are growing, it is worth checking the supply before installing new equipment.
Single-Phase and Three-Phase Supplies
Smaller premises may have a single-phase supply, while larger commercial sites often use three-phase electricity.
Three-phase supplies can support larger electrical loads and are commonly used for commercial machinery and other high-power equipment.
However, having three-phase electricity does not mean the site has unlimited capacity.
The available supply still depends on the connection and its agreed limits.
When Might You Need More Capacity?
You may need to check your supply if you are planning to:
- install several EV chargers
- replace gas heating with electric heating
- add heat pumps
- install new machinery
- expand production
- add commercial refrigeration
- increase the size of the premises
- change how the building is used
The important point is to check before installing the equipment.
Finding out afterwards that the supply is too small can cause delays and extra cost.
EV Chargers
EV charging can add a large new electrical load, particularly where several vehicles charge together.
For example, adding a bank of chargers to an existing commercial site could push demand well above its previous level.
However, increasing the connection is not always the only answer.
Smart charging and load management can sometimes control when vehicles charge so that the site’s existing capacity is used more effectively.
The right solution depends on the site and how the vehicles are used.
Electric Heating and Heat Pumps
Replacing gas heating with electric heating can also increase demand.
Heat pumps are generally more efficient than direct electric resistance heating, but they still add a significant electrical load.
So, if a business is moving towards electric heating, the electricity supply should form part of the project planning.
Do not look only at annual energy use. Check the peak power requirement too.
What Is Load Management?
Load management controls when electrical equipment uses power.
For example, a business may not need every EV charger to run at full power while other large equipment is already operating.
A control system can reduce or delay some loads so that the total demand stays within an agreed limit.
This can sometimes avoid or reduce the need for a larger network connection.
Check Your Actual Demand
If your business has detailed meter data, it may show how demand changes through the day.
Half-hourly data can be particularly useful because it shows when electricity use rises and falls.
This can help you see whether your site is already close to its limit or whether there is unused capacity at certain times.
However, historic use is only part of the picture. You also need to include any new equipment you plan to add.
Can You Increase the Capacity?
Yes, in many cases.
If the existing supply is not large enough, you can ask the local electricity network operator about increasing it.
The work needed will depend on the site and the local network.
A simple upgrade may be possible in some cases. Larger increases can require new cables, equipment or wider network work.
So, costs and timescales can vary considerably.
Who Runs the Local Network?
The company that owns and operates the local electricity network is usually called a Distribution Network Operator, or DNO.
This is different from your electricity supplier.
Your supplier sells you electricity and sends your bill. The DNO operates the local cables and equipment that deliver electricity to the premises.
If you need a larger connection, the DNO or another authorised connections provider will normally be involved.
Can You Reduce Your Agreed Capacity?
Sometimes a business has more agreed capacity than it now needs.
For some larger supplies, reducing that agreed capacity may reduce certain charges.
However, do not reduce it simply because your recent demand has been lower.
Think about future plans as well. Increasing capacity again later may involve cost and delay.
So, check your actual use, planned equipment and likely future needs before changing the agreement.
Avoid Guessing
It may be tempting to add together the power ratings of every appliance and assume that is the capacity you need.
In practice, it can be more complicated because not everything runs at full power at the same time.
This is often called diversity.
Motors and some other equipment can also create high loads when they start.
For anything beyond a simple small-business installation, get the electrical demand properly assessed rather than relying on a rough calculation.
Before Adding Large Equipment
Start by checking your existing electrical supply.
Then list the major equipment you already use and what you plan to add.
Consider:
- how much power each item needs
- which items could run together
- whether demand can be managed
- whether the existing supply is large enough
- whether an upgrade may be needed
An electrician, electrical engineer or suitable connections specialist can help with larger projects.
Key Points
- kWh measures energy use, while kVA is used to describe supply capacity.
- Maximum demand is the highest electrical load placed on the supply.
- Several large loads running together can create a capacity problem.
- Check the supply before installing major new electrical equipment.
- EV charging and electric heating can significantly increase demand.
- Load management can sometimes reduce the need for an upgrade.
- Larger connection changes may need to involve the local network operator.
Important Information
Energility provides general information to help you understand energy, household and business costs, services and ways to save money. It is not financial, legal, tax, technical or professional advice.
Prices, tariffs, grants, government schemes, regulations and other information can change. Costs, savings and calculator results are estimates and your actual results may be different.
Before making an important financial decision, signing a contract or carrying out significant work, check the latest information and consider getting advice from a suitably qualified professional where needed.
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