At a glance
đ There's no legal limit on the number of rooftop solar panels you can have
Assuming your property doesnât require planning permission for a solar installation, there is no legal maximum number of solar panels that you can install on your roof in the UK.
Other thanusable roofspace, there is nothing limiting how many solar panels you can put up there.
Listed buildingsand properties in conservation areas usually requireplanning permissionfor solar panels, but for the majority of other homes a solar installation counts as a âpermitted developmentâ.
⥠An installation is more likely to be limited by practical considerations
Most households are limited to some degree by the amount of useful roof space they have.
Issues include how much physical space is up there, which direction different parts of your roof face, and whether space needs to be left so that items like chimneys don't cast a shadow over your panels.
Fortunately, the majority of homes can still get enough solar panels installed to save them hundreds of pounds per year.
đ You will need permission from your DNO for an inverter with a capacity over 3.68kW
In the UK, any inverter larger than 3.68 kilowatts (kW) requires permission from the local Distribution Network Operator (DNO) before it can connect to the grid. To acquire this permission, you need to submit an application called a G99.
If the inverter is 3.68kW or smaller, youâre able to simply âconnect and notifyâ without needing permission (this is called a G98).
For systems with inverters larger than 3.68kW, Sunsave will fully manage the DNO application process on your behalf.
đ You can get a bigger inverter if you have a three-phase electricity setup
âSingle phaseâ and âthree phaseâ refers to different sizes of electricity supply feeding from the grid into a property.Single phase means the property receives electricity through one wire, and this is what most households in the UK have.
Three phase means the property receives electricity through three separate wires. This is far less common, and is only typically necessary for commercial buildings and households that use a huge quantity of electricity. Three-phase systems can deliver a higher sustained power output, making them better suited for heavy machinery or larger electrical loads.
The electricity output limit in the UK is actually 3.68kWper phase,but single-phase properties are so common that itâs essentially the same as an inverter limit. However, if your property has three-phase power, you could have an inverter as big as 11kW before youâd require DNO permission.
đ Adding solar panels at a later date is technically fine â but not advised
You can add more solar panels at a later date, as long as there are no planning permission-related barriers, but it's more cost effective to plan ahead and get a bigger system installed upfront, so you avoid paying twice for fixed costs like labour and scaffolding.
Installers need scaffoldingto get up onto your roof safely, and its setup/take-down costs can be a sizable chunk of the total expense.
When you install a larger system initially, you can split the fixed costs among more solar panels, which ends up reducing the cost per panel.
If youâre thinking of switching to solar, youâre probably wondering how extensively you can cover your roof with solar panels. Given youâll be paying the fixed costs of scaffolding and installation, it makes sense to make full use of your propertyâs roof space.
In this article, weâll explain how many solar panels you can have before you start dealing with various practical considerations, building regulations and DNO requirements.
If youâre interested in finding out how much a solar & battery system could save you, answer a few quick questions below and weâll generate an estimate for you.
Whatâs the maximum number of solar panels you can have in the UK?
Assuming your property doesnât require planning permission for a solar installation, there is no legal maximum number of solar panels that you can install on your roof in the UK. Other than usable roof space, there is nothing limiting how many solar panels you can put up there.
Listed buildings and properties in conservation areas usually require planning permission for solar panels, but for the majority of other homes a solar installation counts as a âpermitted developmentâ.
However, it is a legal requirement of all rooftop solar panel installations that no panel sits closer than 400mm from the edge of the roof. This means you canât actually cover every square inch of your rooftop.
If your rooftop isnât suitable for some reason (e.g. itâs a flat roof, or completely north-facing) and you opt for a ground-mounted system, any system exceeding nine square metres requires planning permission.
So, while there's no hard limit on rooftop solar installations, practical considerations and regulations should guide your decision. Most typical three-bedroom or four-bedroom homes usually have systems that range from 4 kilowatts peak (kWp) to 6kWp.
đ¤ Thinking of going solar? Here's why a larger system makes sense âŹď¸
When youâre switching to solar, it's worth getting as large a solar & battery system as you can.
A few extra solar panels won't add much to the overall cost, but in most cases they'll have a big impact on your energy bill savings.
And for the majority of homes, a larger battery will significantly increase the value you get from your solar panels.
To understand all the key reasons in detail, check out the articles below.
Related Reading
4 reasons to get a larger solar panel systemBy Josh Jackman9 August 20245 reasons to get a larger storage batteryBy Josh Jackman9 August 2024Is there a limit on how much solar electricity you can generate?
A solar panel system's capacity isn't limited to a certain number of panels, but there is a limit on the size of the systemâs inverter.
The inverter is what converts the electricity from direct current (DC) to alternating current (AC), and consequently makes it usable in your home (or exportable to the grid). You could have a vast solar panel array, but itâs the size of the inverter that will dictate the systemâs actual output.
In the UK, any inverter larger than 3.68 kilowatts (kW) requires permission from the local Distribution Network Operator (DNO) before it can connect to the grid. To acquire this permission, you need to submit an application called a G99.
If the inverter is 3.68kW or smaller, youâre able to simply âconnect and notifyâ without needing permission (this is called a G98).
For systems with inverters larger than 3.68kW, Sunsave will fully manage the DNO application process on your behalf.
The UK's first solar subscription
- No upfront cost
- Fixed monthly fee
- 20-year Sunsave Guarantee
Learn more
Why is there a limit on solar PV output?
The limit on solar output is in place to prevent issues with grid stability.
A sudden influx of new electricity generation, from solar panels and elsewhere, can cause grid fluctuations in voltage and frequency, which can lead to instability and potential blackouts.
But by regulating this output, grid operators can make sure everyone gets a balanced and reliable supply of electricity.
How do you apply to your DNO for permission?
The solar panel installation process typically involves submitting an application with details of your plans to your local DNO to ensure grid compatibility and safety.
In the UK, there are six DNOs covering 14 different district networks:
- Electricity North West Limited
- Northern Powergrid
- Scottish and Southern Energy
- ScottishPower Energy Networks
- UK Power Networks
- Western Power Distribution
To find out who your local DNO is, you can use the Energy Networks Association search tool.
How likely is DNO approval?
The majority of solar panel systems that require a G99 application are accepted, but some DNOs will ask for an additional fee in order to cover any necessary grid work.
This work can include transformer upgrades, new cables, and other equipment to ensure the grid can reliably accommodate the solar exports from your system.
However, if your inverter is smaller than 3.68kW then you wonât need to worry about any extra fees, as you can just connect to the grid and start exporting immediately.
How long does DNO approval take?
DNO approval for solar panel systems typically takes around 4-6 weeks.
During this time, your local DNO will assess the proposed system's impact on the local grid and decide if any upgrades are necessary to accommodate your potential solar exports.
The time frame might be affected by things like how complicated the application is and how busy the specific DNO is.
However, your solar installer should be familiar with each DNOâs approval process and take all the necessary steps to keep things moving forward.
Could you choose not to connect to the grid?
While it's technically possible to go "off-grid" with a solar & battery system, choosing not to connect your system to the grid isn't recommended. A grid connection is essential for reliability, flexibility, and financial benefits.
For instance, without a grid connection, you'd have no access to grid-supplied electricity during times of low solar generation, which means you'll need to rely solely on battery storage to power your home. This can be costly and may require a larger, more complex battery system.
Also, you won't be able to export excess electricity, which means you'll miss out on potential earnings from solar export tariffs that can help offset the cost of your solar panel system over time.
Single-phase vs three-phase solar installations
âSingle-phaseâ and âthree-phaseâ refers to different sizes of electricity supply feeding from the grid into a property.
Single-phase means the property receives electricity through one wire, and this is what most households in the UK have.
Three-phase means the property receives electricity through three separate wires. This is far less common, and is only necessary for commercial buildings and households that use a huge quantity of electricity. Three-phase systems can deliver a higher sustained power output, making them better suited for heavy machinery or larger electrical loads.
The electricity output limit in the UK is actually 3.68kW per phase, but single-phase properties are so common that itâs essentially the same as an inverter limit. However, if your property has three-phase power, you could have an inverter as big as 11kW before youâd require DNO permission.
If youâre not sure whether you have a single-phase or three-phase power supply, take a look at your electrical fuses. Single-phase supplies will have one fuse, whereas three-phase supplies have three.
Can you add more solar panels to your system later on?
You can add more solar panels at a later date, but it's more cost effective to plan ahead and get a bigger system installed upfront, so you avoid paying twice for fixed costs like labour and scaffolding.
Installers need scaffolding to get up onto your roof safely, and its setup/take-down costs can be a sizable chunk of the total expense.
When you install a larger solar panel system, you can split the fixed costs among more panels, which ends up reducing the cost per panel.
Summary
Installing solar panels offers many benefits, and it makes financial sense to get as many panels as possible once your scaffolding is set up.
Providing the panels donât sit closer than 400mm from the edge of your rooftop, you can install as many panels as you want.
Wondering how much a solar & battery system could save you? Simply answer a few quick questions below, and weâll calculate an estimate.
Maximum number of solar panels: FAQs
Is there a limit to how many solar panels I can have?
There's no legal limit on the number of solar panels you can have in the UK, providing you have planning permission and that your panels adhere to building regulations.
However, you may find your system limited by practical constraints, like your available roof space, budget, and local regulations.
The key to getting the most out of your panels is to use your roof space effectively, considering factors like potential shading and their optimum positioning so you can generate as much solar electricity as possible.
Related Reading
How many solar panels do you need?By Josh Jackman29 August 2024Whatâs the DNO solar limit?
The DNO solar limit refers to the maximum capacity of a solar panel inverter that can be connected to the grid without special permission. In the UK, this limit is 3.68kW per phase.
This means that properties with a single-phase supply are limited to a 3.68kW inverter before having to submit a G99 application, whereas households with a three-phase supply could have an 11kW inverter before requiring permission.
Larger solar panel systems need approval from the DNO to ensure grid stability and safety.
Related Reading
DNO solar applications: the expert guideBy Josh Jackman13 August 2024Can you put on too many solar panels?
Although more solar panels would increase your electricity generation, this excess output is worthless if your inverter isnât large enough to accommodate it. There are also parts of your roof that arenât worth putting solar panels on, for example any north-facing sections.
It's best to work with a professional installer who can help you decide on the right size for your solar panel system. They will provide personalised advice based on factors like your roof space and how much electricity you use.
Related Reading
How many solar panels do you need?By Josh Jackman29 August 2024Related articles
Planning permission for solar panels: an expert guide
Read full story
DNO solar applications: the expert guide
Read full story
Solar panels in conservation areas: the expert guide
Read full story
Building regulations for solar panels: explained
Read full story
Written byMelody Abeni
Based in London, Melody is a specialist green technology writer who has been covering sustainability, climate action and ESG for the past five years, after gathering operational experience in green investing and financial services. She has written for various industry publications, including renewable technology advisor The Eco Experts, and she holds a Masterâs degree in law from Birkbeck University.