HV vs LV Voltage Systems
A practical guide for developers, contractors and project managers
Understanding the difference between High Voltage (HV) and Low Voltage (LV) systems is essential when planning any
new connection, upgrade or multi-utility installation. The voltage level directly affects cost, design requirements,
timescales and the type of provider you need on board.
At AIS Utilities, we work across both HV and LV networks nationwide, so here is a clear and simple breakdown of how
each system works and when you are likely to need them.
What Is Low Voltage (LV)?
LV refers to electrical supply voltages up to 1,000 volts AC. In the UK, this usually means:
- 230 V single phase
- 400 V three phase
Where LV Is Commonly Used
LV supplies are typical for:
- Standard homes
- Small commercial units such as shops, cafés and small workshops
- Small EV chargers
- Low demand industrial units
- Most minor refurbishments or new builds
Benefits of LV
- Usually cheaper to install
- Faster design and approval process
- Equipment and cabling are simpler
- Ideal for sites with modest power needs
When LV Might Not Be Enough
If your site has large motors, heavy machinery, high heat loads or large EV charging hubs, LV may not provide
sufficient capacity.
What Is High Voltage (HV)?
HV refers to electricity typically between 11 kV and 33 kV on distribution networks. This is the level used by
Distribution Network Operators (DNOs) to deliver large amounts of power across the network.
Where HV Is Commonly Used
HV supplies are required for:
- Large industrial units
- Commercial estates
- Major residential developments
- Supermarkets and data centres
- Solar farms and battery storage sites
- Large multi unit EV charging hubs
- Sites with significant peak loads
Benefits of HV
- Delivers much higher capacity
- Supports long cable routes without significant losses
- Suitable for future expansion and load growth
- Enables dedicated, private HV networks on large sites
Challenges of HV
- Higher installation cost
- Specialist design and equipment required
- Additional protection and switching systems
- Longer DNO approval and Point of Connection (POC) timescales
Do You Need HV or LV? How to Tell
You will likely need an HV supply if:
- Your maximum demand is above 300 to 500 kVA
- You are installing many EV chargers, especially rapid chargers
- You are building a large warehouse, industrial unit or mixed use development
- The DNO advises that the network requires HV reinforcement
- The site is far from the nearest LV network
If your load is modest and close to an LV feeder, an LV connection is usually suitable and more cost effective.
Costs and Timescales: What to Expect
LV Connection
LV projects are generally quicker and more affordable. They work well for most small and medium developments where
the power demand is predictable and the design is relatively simple.
HV Connection
HV connections require more specialist equipment such as substations, switchgear and protection systems, which
naturally increases the cost. They also tend to have longer timelines because there are more steps involved in
design, approvals and energisation. The timelines are also longer because the DNO needs to be more involved in the
design, the Point of Connection process and the final energisation. HV is typically recommended for sites with high
power demand or for sites expected to expand in the future.
How AIS Utilities Supports HV and LV Projects
AIS Utilities is fully accredited under NERS, GIRS and WIRS, delivering end to end multi-utility
solutions across the UK.
Our HV and LV services include:
LV Services
- LV design and load assessments
- LV cable installation
- LV cabinets and cut outs
- Final connections and energisation
HV Services
- Full HV design
- Point of Connection (POC) applications
- HV cable installation
- Substation builds
- Transforming HV to LV for site distribution
- Testing, commissioning and energisation
We manage everything from initial capacity checks to final handover.
Frequently Asked Questions
Is HV always more expensive?
Generally yes, due to specialist equipment, substations and the level of engineering involved.
Can a site upgrade from LV to HV later?
Yes, but it is usually more cost effective to plan HV early if you expect future load expansion.
Who decides whether the site needs HV?
The DNO ultimately confirms the voltage level when they issue your Point of Connection (POC). However, AIS Utilities
can advise based on early load assessments.
Do EV chargers need HV?
Small quantities of slow chargers can run on LV. Rapid chargers, hubs and fleets almost always need HV.
Need Help With Your HV or LV Connection?
AIS Utilities supports developers, ICPs and main contractors nationwide with complete multi-utility design and
installation.
- NERS, GIRS and WIRS accredited
- Full HV and LV capability
- POC applications handled for you
- Fast design turnaround
- End to end project delivery
