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11 Apr 2024

Do you need a 3-phase power supply to install solar panels?

Anna Dearden
Home Sector Specialist

Solar panels have become more affordable than ever in the UK. With PV panel prices plummeting and energy prices soaring, now is the perfect time to explore the benefits of solar panels. This shift in affordability brings with it the promise of significant cost savings on your energy bills. If you're contemplating this eco-friendly switch, you might be wondering if a transition to 3-phase power is necessary. You might have heard the terms single-phase and 3-phase power supply before. If you’re not too sure what they mean, don’t worry — we’re here to help. 

Most homes in the UK have a meter tucked away in a cupboard. The easiest way to check your power supply is to count the number of wires. There are usually two, meaning you have a single-phase system. Alternatively, in a three-phase system, you’ll find three live wires and fuses. But if you're installing solar panels, is that powerful enough? 


In this article, we’ll examine 3-phase power in more detail. Will you need to upgrade if you install solar panels? And how much does a typical 3-phase supply installation cost in the UK?  

What is 3-phase power? 


Three-phase systems are rare in the UK. Most homes operate on a single-phase supply with one fuse and one meter. But if you typically require more power at a faster rate, such as for running heavy machinery or charging electric vehicles, a 3-phase power supply could be the solution. 


But what is a 3-phase power supply? Put simply, a 3-phase power system uses three live wires and three fuses, hence the name. Three-phase systems are standard for larger buildings with more significant energy needs, such as industrial units and offices. If you live on a farm or in a large house, you may also be on a 3-phase power supply. 


Single-phase power systems are standard in UK homes and are suited to lower electricity usage. These systems are designed to efficiently meet the needs of the average home or small business.


Do you need a 3-phase power supply for solar power installation? 

As the number of homeowners seeking to reduce their energy bills continues to rise, the popularity of generating green energy is skyrocketing. So, do you need 3-phase power for solar panels?  


The good news is that you won't need to make the switch to benefit from clean energy generation and lower bills. Installing a domestic solar panel system is straightforward and can be done without changing your power supply, providing you with peace of mind. 


However, a lot depends on the size of your solar panel system set-up. Inverters are essential, converting the direct current (DC) your solar panels generate into the alternative current (AC) electricity used in your home. This process ensures solar energy is compatible with your home's power supply.  


As a result, most domestic systems use a single-phase inverter for seamless connection to your electricity supply.  


Being on a single-phase supply won’t be a problem for most home users. A 3.5kW solar system is more than adequate to meet the needs of an average three-bedroom home. On the other hand, property owners with a 3-phase solar system in the UK can generate up to 11kW of power using a 3-phase power converter. 


So, does adding a solar battery to your system warrant switching your power supply? Supplementing your system with storage batteries is well worth it. And if you already have 3-phase power, a larger battery is a worthwhile investment.  


Fortunately, you won’t need to switch to three-phase power to enjoy the benefits. Your solar battery simply stores energy that’s already passed through the inverter. Assuming you have the right inverter for your system and energy needs, you won’t need to change from single-phase to three-phase.  


Is single-phase or 3-phase power better for solar panels?  

While single-phase power is sufficient for most households, a 3-phase power supply delivers an efficient and stable energy flow. Understanding the advantages of 3-phase power can help you to make an informed decision about upgrading. As a result, you can have confidence knowing you're making the right choice for your energy needs. 


A key advantage of a 3-phase system is its higher power capacity. This makes it suitable if you plan to install up to 11kW solar PV panels, power a 22kW EV charger, or run power-intensive appliances. It's the best solution if your home or business has larger energy demands.  


Three-phase systems virtually eliminate voltage inconsistencies, making them better balanced and more efficient than single-phase systems. Three wires minimise resistive loss for a more stable power supply. As a result, a 3-phase power supply is a good choice for a more extensive solar panel set-up with batteries, distributing power evenly throughout the building and giving you more energy on tap. 


Of course, there are downsides. Installation can be complex and costly, involving digging up and replacing external wires. Unfortunately, switching power supply isn’t just a question of adding more fuses. 


Alternatively, a single-phase system with an inverter is far more versatile for domestic or light commercial use. Single-phase solar energy is also an ideal solution for remote, off-grid systems. 


But what other factors are involved when choosing between single-phase and 3-phase solar systems in the UK? It’s worth noting that your grid connection plays a significant role in the decision. As an example, a 4kW system can be connected without permission. However, adding a battery could increase your export capacity by 50%, requiring the consent of your Distribution Network Operator (DNO).  


While the size of your current solar system may be limited by available space, what about future expansion plans? As solar panels become increasingly efficient, consider upgrading your system to meet future power demands. With this in mind, installing a 3-phase system now would be a solid long-term investment, ensuring you're prepared for future energy needs. 


Ultimately, which power supply suits your system best is a pivotal decision that should align with your specific power needs — now and in the future. 

How much does a 3-phase power supply cost in the UK?  

It's also essential to think about the financial aspect of upgrading to a 3-phase power supply. The transition from a single-phase supply to a 3-phase can range from £3,000 to £8,000, depending mainly on the complexity of the installation. It's a significant investment that could be worthwhile if your energy needs are high.  


First, contact your DNO to request an upgrade to a 3-phase power supply. If you're not confident with the paperwork, your electrician should be able to handle the application for you. Once the DNO gives the go-ahead, you’ll need to replace the existing cables to your property. Once installed, your fuse and electricity meter will need replacing, and your home circuits will need rewiring. 


The entire process, including the initial application and survey, generally takes two to three weeks. Replacing the underground cables and rewiring them will take a few days.  


However, the upgrade will take longer and cost more if the work is more complex. For instance, the cables connecting your home to the grid may run under public footpaths, requiring work permits from your local authority. Your costs will also be higher the further your home is from the nearest 3-phase electricity supply. 


Upgrade your home with a solar panel system: Compare and save with SpotDif  

Ready to upgrade your home with a solar panel system? Compare and save on solar panel quotes from trusted suppliers in your postcode. We’ll help you assess your energy needs and determine whether a 3-phase power supply is necessary for your solar panel installation. 

Then, we’ll compare the best solar panel deals in your area and find money-saving deals you’ll love.  Get started with SpotDif today.

Anna Dearden
Home Sector Specialist
Combining in-depth research with an interest in all things home improvement, I aim to keep SpotDif readers up to date with interior design trends, renewable energy options, and more.
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