Solar Power Output UK: How Much Energy Do Panels Produce?

The use of solar panels among domestic properties is on the rise in the UK.

...and for good reason.

Not only are solar panels a renewable and eco-friendly source of energy generation but they can drastically reduce electricity bills for homeowners (find out exactly how much here). 

Moreover, solar panels can even bring in money if households decide to sell their excess electricity back to the grid via the Smart Export Guarantee. 

But how much energy can solar panels produce in the UK? And how does their power output differ in winter vs summer?

Let’s explore...

PS We offer MCS-certified solar panel installation nationwide. Simply answer these questions, get your fixed price and arrange your free design.

Solar Panel Power Output Key Points: 

• Solar panel power output is measured in kilowatts peak (kWp).

• Actual power output varies based on location, orientation, shading, and temperature.

• A 4 kWp solar panel system in the UK generates around 3,400 kWh per year on average.

• Solar panel efficiency ranges from 15-22% on average.

• Consult with an expert to determine the specific power output for your situation.

How much energy do solar panels produce in the UK?

A solar panel's energy production is defined by its power output, which is measured in watts.

The greater the wattage of the panel, the more electricity it is able to produce.

Please bear in mind that the amount of energy generated is also influenced by other factors, including the position and angle of your roof and your property's location within the UK.

The average solar panel in domestic installs is 350 W and the average size solar array is 3.5 kWp, which on average takes around 10 panels in total.

In the detailed scenario illustrated in the next section, we show how this sized solar array would be able to produce around 3,251.50 kWh of electricity annually.

How much energy can a solar panel system generate for you? 

Again, this depends on a variety of factors including your location, roof size, and the types of panels you use. 

However, in general, a solar panel system should be able to provide around 50% of your annual energy demands. 

You can potentially increase the amount of energy you can use from your solar panels by pairing it with solar battery storage. 

For reference, we will now explore some actual numbers with worked examples:

*The methodology and data used are sourced from MCS and as noted are based on a series of assumptions. Figures last updated: June 2023.

Why do solar panels not produce 100% of your energy?

Solar requires sunlight to generate electricity, as a result, it only produces energy during the day.

This means you must consume the electricity generated during daylight hours, which means the solar can't power your energy demands in the evenings/at night. 

However, a solar battery can help to alleviate this major barrier and enable you to store the energy your solar panels generate for use later i.e. in the evenings. 

Explore a Solar Case Study: Check out an insightful Q&A session featured in one of our detailed case studies on domestic solar panels. Hear directly from a Heatable customer in the UK and gain valuable perspectives on their experience here.

The image above shows a 23-panel solar installation, carried out by the MCS-certified solar team at Heatable, featuring the REA Fusion2 solar panels.

Solar Power Output in Winter Vs Summer UK 

Solar power output can change during the year and this is based on the sunlight exposure changes throughout the seasons. 

For example, in summer, there is around twice as much sun exposure as there is in winter. 

Why? 

Days are shorter during winter and the sun itself is lower in the sky, both impacting the amount of sunlight your panels are exposed to vs the summer months. 

One way to alleviate this is by using a low light optimised system.

These systems use high-efficiency, low-light-optimised solar panels combined with microinverters and are the best for winter performance. 

Factors  Impacting Solar Panel Power Generation

As touched on there are many factors that determine how much electricity any given solar system will actually produce in a year.

Quality of the Solar Panels

Not all solar panels are built equally.

Many solar panels on the market offer a wattage in the range of 350-390, however, you’ll also find examples like the REA Fusion Power which could go much further than that. 

In the case of the REA Fusion Power, it offers 420 watts and features a bi-facial design that is optimised for low light conditions. 

For that reason, you’d only need five of these panels to create a 2kW system, whereas you’d generally need eight panels to reach that level of energy production.

As a result, the higher quality your panels are (and specifically the more durable they are), the more of the original output they’ll offer after say 5 years, 15 years, or perhaps even 40 years.

Weather Conditions 

All solar panels are susceptible to weather changes.

Naturally, solar panels capture more solar energy on bright sunny days and less on days that are overcast.

Solar energy can still reach solar panels on a cloudy day, however, cloudiness can put a fairly significant dent in solar electricity production.

In fact, on average solar panels produce just 10-25% as much electricity on an overcast day as they do on a sunny day. Put another way, this would represent an output reduction of 75-90%.

However, there is a solution to this problem and that is to utilise a system optimised for low light conditions. 

For example, the system we offer is one such system, the solar panels themselves are optimised for low light but also use microinverters, as they can switch on to convert the energy at a much lower voltage i.e., you can make use of the lower voltage production which a traditional DC inverter cannot do.

In our testing, the REA system performs by as much as 15% better than a traditional DC system in these settings.

Still, learning about solar? Check out our guides on how many solar panels you need and how solar car charging works. 

Roof Direction and Angle

Another factor that should not be overlooked is the direction/angle of your roof.

Firstly, solar panels should ideally be installed on a south-facing roof. What’s more, solar panels work best if fitted on a south-facing roof at an angle of 35°.

With that said, even if you have a west-facing or east-facing roof, solar panels can still be worth the investment if installed at an angle between 10° and 60°.

It won’t give you as strong results as you’d get with the ideal conditions, but an east- or west-facing roof can still offer a reasonable level of energy generation.

Shade

Shade is the solar system's worst enemy. Therefore, you need to carefully take this into account when having your solar panels installed.

In addition, even if you have your panels installed in a great spot, to begin with, shading concerns may arise over time.

For instance, if you have a tree on your property, watch out for overhanging branches that could emerge over time and pose a shade risk to your solar panels. 

The good news is that any shading issues either from chimneys, roof structures, or trees can be combatted by installing solar panel optimisers, however, they do cost around £100 to be supplied and installed per panel.

If the panels aren't optimised, the panels connected on the same circuit as the shaded panel will see a drop in performance even though they are not shaded.

On a side note, the REA system supplied by Heatable does feature full optimisation as standard meaning no additional components are required.

Debris

Overhanging branches not only risk shading a solar system but during stormy weather, they could prove a debris hazard.

While shading can be inconvenient for a solar system, debris could result in damage that would necessitate expensive repairs or even the replacement of some solar panels.

Of course, storm debris in general is something to watch out for.

That’s why you should ideally have your solar panels cleaned once or twice a year or any time after significantly harsh weather.

If you are researching solar panel companies, you may find our resources valuable. Check out our comprehensive comparison of the best solar panel companies in the UK, learn about the Distribution Network Operator (DNO) process, and explore our detailed solar panel guide and solar advice section for expert insights and recommendations.

How many solar panels do I need?

The number of solar panels you’ll need will primarily depend on your energy needs and the quality of the panels you want.

Some people choose to have a solar panel array installed to supplement their energy needs (i.e., they’ll use solar panels for say half of their electricity requirements while covering the rest with the national grid).

This way homeowners can reduce their electricity bills without splashing out on the number of panels needed to cover all their electricity needs.

Alternatively, you may want to have enough panels fitted to cover all your electricity requirements or even to go beyond that and ensure a surplus of energy.

In the case of the latter, you’d then be in a position to sell electricity back to the grid via an energy provider (assuming you meet all the criteria).

Here’s how many 350-watt solar panels you’d likely need to meet all of your electricity needs:

The above estimate is just that. Ultimately, it’s best to consult with a professional to determine how many solar panels you’ll really need.

Also, it tends to be best to have more solar panels than you think you’d need if you want to rely almost entirely on solar energy. 

Of course, it would be best to maintain connectivity with the national grid either way in case of many overcast days in a row.

We have also reviewed the best solar panels and covered how long solar panels last in the UK. 

Furthermore, another consideration is whether or not you’d like to have a solar battery for storing energy.

This would be helpful for those cloudy days as it would mean you could store excess energy from sunny days and use it to help power your home when the weather worsens.

Solar battery storage can also play a part in selling electricity back to the national grid (if this interests you).

The UK’s mandatory SEG licensees are as follows:

• E

• British Gas

• OV Energy

• The Utility Warehouse

• EDF

• Bulb

• E.ON

• Shell Energy

• Octopus Energy

• Scottish Power

• ESB

• Utilita

Next Steps For Your Solar Journey:

When planning to install solar panels for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:

• How much do solar panels cost? 

• Are solar panels worth it for your home? 

• Is your roof suitable for solar panels? 

• What are the best solar panels available? 

• Is battery storage worth it? 

To dive deeper into these topics, head over to our advice section, check out our YouTube channel for informative videos, or read a customer case study to see how others have benefited from their solar installation. 

Get a Quote for Solar Today 

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• MCS Accredited: Our accreditation by the Microgeneration Certification Scheme (MCS) ensures high-quality standards.

• Exclusive Panels: We offer REA Fusion solar panels, available only through Heatable.

• Consumer Protection: As members of the HIES consumer code, we provide 2-year deposit protection.

• Flexible Payment Options: Choose from multiple payment methods, including finance options.

• Fixed Price Guarantee: Enjoy transparency with no hidden costs.

• Save Your Quote: You can save your quote and decide later.

• Bespoke Design Tool: Draw your own conclusion (literally) on whether solar is worth it for you, here.