How Much Electricity Does a Solar Panel Produce, UK?

Written-by

Janet Richardson

Reviewed-by

Richard Burdett-Gardiner

Updated on

Sep 29, 2024

How Much Electricity Does a Solar Panel Produce, UK?

According to Statista, in 2023 UK solar panels generated an impressive 15,225 gigawatt hours of electricity. That means solar PV (photo voltaic) panels produced about 3% of the UK’s electricity last year. Now, that may not sound like much, but remember in 2004 the number of gigawatt hours generated by solar was just four. That’s not 4000 or 400, not even 40, in 2004 the number of gigawatts produced was four! These days, as the efficiency of solar panels improves and the costs shrink, it’s safe to say that number will only grow.

There are many reasons why solar panels are growing in popularity, due in part, to the increasing amount of energy a solar panel can produce. They are safe, green, dependable, and affordable and it’s no wonder so many UK homes and businesses are switching to solar. If you’re unsure about making the change yourself, it may help to know how much power a solar panel system generates, and what kind of output you need.

Watt are we talking about?

Before we go on, let’s sort the jargon. In this article, we’ll look at the solar panel output of various systems.  The industry terminology used to describe these figures is Kilowatt hours and you’ll often see it broken down like this:

• Watt (W) – the measure of power output of the system or panel. 
• Kilowatt (kW) – 1,000 Watts
• Kilowatt-hour (kWh) – the energy, or potential energy, produced in an hour.

We’ll also discuss a specific type of solar panel known as photovoltaic panels or cells. In this article, we’ll shorten that term to PV or solar PV.

How much energy do domestic solar panels generate?

This is a big question and there are many factors to consider before we get to a definitive answer.  As you’d expect in a blossoming market there are a lot of different options and solar panels come in many styles and sizes. In this article, we’ll focus on solar PV or Photo Voltaic cells. This a subset of solar panels designed to draw electrical power directly from the sun and doesn’t include solar thermal panels. Solar thermal panels, by contrast, use the sun’s energy to heat water. If you want to read more about solar thermal panels check out our guide here.  

Even in the solar PV cell camp, there’s a wide range of different designs. This makes answering the simple question of how much power a solar panel generates a bit complicated, but we’ll do our best.   

In the UK, most domestic solar panels fall between the 250W and 400W categories. Taking the mean then, the standard size for a common 350W solar PV panel is approx. 1,9m long and 1m across.

As mentioned, the exact amount of power generated by any given panel depends on the following factors:   

• The pitch and orientation of the property’s roof. 
• The amount of daylight, or solar irradiance in the local area.
• Any obstructions or shade that affect the array. 
• How clean and well-maintained the panels are.
• The size and type of the panels installed.

We’ll take a deeper dive into each of these factors in a moment, but for now, let’s answer the basic question. 

Logically then, an average 350W single solar PV panel can potentially generate 350 watts of power per hour, or 0.35(kWh). Of course, this figure is the best-case scenario and assumes the panel is operating under ideal conditions. This is a rose-tinted view and it’s safe to say we can take those numbers with a pinch of proverbial salt, especially in sun-starved Blighty. 

Watt’s it good for?

One important fact to note is that no solar panel system in the UK relies on a single panel. One 350W panel would struggle to power your TV for an hour. Most solar systems in the UK comprise multiple PV panels and it’s the combined output of the system that matters.   

How much power do I need from solar panels in the UK?

When working out the size of your solar system and how much energy it can produce, you need to know how much power you use. The easy way to work this out is to look at your past consumption. You can ask your electricity provider for old bills. Or if you have one, take notes from your smart meter.  Of course, there are plenty of resources online where you can find UK stats and averages to help get you rolling. Here are some numbers from Ofgem to give you an idea:

Typical annual electricity use (kWh)

Low: Flat or 1-bedroom house; 1 or 2 occupants
1,800 (kWh)

Medium: 2–3-bedroom house; 2 or 3 occupants 
2,700(kWh)

High: 4-bedroom home; 4 or 5 occupants
4,100(kWh)

Every solar panel array in the UK is different and working out the exact energy produced is tricky. That said, here are some standard facts for an average, UK domestic solar panel system.

Domestic solar systems range from 1 kilowatt (kW) to 5kW in power.

• 1kW systems generate around 850 kWh/s per year
• 2kW systems generate around 1,700kWh/s per year 
• 5kW systems generate around 4,500kWh/s per year

So, now we know how much energy a typical household uses per year let’s look at how much energy a typical 4kW solar PV / solar panel system generates. If we take a low-energy household, let’s say a single occupier one-bedroomed flat, then it looks like they’d get by with a 2kW solar array. Whereas a bigger, high-energy household, in say a four-bedroomed house would need a 5kW system at least to cover 50-70% plus of it's electrical demand.

Now, we’re still talking about these systems performing under perfect conditions. As we all know, life has a habit of getting in the way of things like that.

Generally speaking, a 4kW solar panel array will be able to produce enough energy to provide about 50-70% of the average UK household's demand . A 2kW or 3kW array, on the other hand, will be able to supply about 25-50% of the average UK household demand. Keep in mind, how much electricity you use, and the way you use it will determine how much your solar panels can cover. A 4kW system will, on average, generate approx. 4500kWh of electricity per year. When we break that down, we can see that it can be enough to provide:

• 6000 hours of the washing machine
• 120,000 hours of running a fridge
• 2600 hours of boiling the kettle
• 2000 hours of running an oven

To estimate the annual energy production, you can use the following formula:
Annual Energy Production (kWh) = System Size (kW) × Daily Sunlight Hours × 365

Daily 4kW solar PV system output in the UK:

In the UK, a 4kW solar PV system, using this equation may generate 10-16 kWh per day, depending on the time of year. 
4kW×2.5 − 4hours = 10−16kWh

This estimate accounts for the lower average number of peak sun hours in the UK, which ranges from about 2.5 hours in winter to 4 hours in summer.

Annual 4kW solar PV system output in the UK: 

For a rough estimate, if you assume an average of 4 sunlight hours per day, the annual energy production would be:
4 kW × 4 hours/day × 365 days/year = 5,840 kWh/year

This is an equation for calculating the max output of a solar array in optimal conditions. In reality, factors like panel efficiency, shading, the angle and direction of your panels, weather conditions and solar irradiance all impact the actual electrical output. To get a more accurate estimate, it's recommended to consult with a local solar installer. 

What affects the power output of solar panels in the UK?

We touched on this earlier. Lots of factors can affect the efficiency and overall output of a solar pv system. Let’s look at each of them in detail now.

Orientation
The biggest issue facing any solar array is its location. To make the most of the sun’s rays, each panel needs direct sunlight. The best way to achieve this is positioning your panels so that they face due south. Of course, not every location has a south-facing roof and it's still possible to benefit from solar power if you don’t. Other aspects, however, will affect your system’s performance.
Generally speaking, any orientation from east to west through south is usable. 

Size
Or Watts installed. This is the most important factor out of the four, as the larger the system is, the more electricity it will produce. If you are looking at a typical installation, it is a 4kW system and this tends to be around 10-14 panels. Alternatively, a 1kw domestic system is likely to only be 3-4 panels.

Where you live
If we lived in a warmer climate, there’s a good chance you’d already have solar panels. Even in the UK though, the amount of daylight hours varies. As you’d expect, the south of the country gets more sun in general.  Even in areas like Scotland though, there’s still enough daylight to justify installing a solar system. 

Obstruction / Shading
As mentioned above, solar panels need direct sunlight to operate at peak efficiency. Therefore, obstructions like trees, other buildings, and even chimneys can reduce efficiency.

Maintenance 
Well looked after and cleaner panels function better than those left to the elements. Dirt and debris like fallen leaves can obscure your cells and cause your system to suffer. 
Seasons: The time of year can also have an impact on efficiency and energy production. During the summertime, there are longer hours of daylight, so you will be able to produce a lot more power. However, it is also important to remember that solar panels actually work by capturing light as opposed to heat, so it will produce energy throughout the year.

The size, type, and style of your panels
We’ll investigate the different kinds of panels in the next section, but there are many makes and models too. It’s a good idea to look at reviews of the various manufacturer's panels and inverters before deciding on what to go for. 

The different kinds of solar panels

For a deeper dive into this subject check out our solar panel guide. For now, though, we’ll cover the basics. Once again, we’re only looking at solar photovoltaic cells (solar PV). 

Monocrystalline silicon solar panels
The most effective, widely available, solar PV cell is monocrystalline silicon. Boasting anywhere from 15 to 20% efficiency, these panels are easy to spot thanks to their sleek black look. Their increased efficiency means they generate more power per square metre than other panels and they’re also smaller as a result. They are more expensive than other panels and less kind to the environment due to their wasteful manufacturing process. On the bright side, they do boast a fifty-year shelf life, the best of any solar PV cell on the market.

Polycrystalline (or multi-crystalline) solar panels
The next best panels in terms of efficiency are polycrystalline solar panels. With an efficiency hovering around 13%, these low-cost panels are better for people with room for larger arrays. They’re greener in a manufacturing sense as their creation doesn’t involve a lot of waste. Polycrystalline panels have a blueish tinge and tend to be bigger than their more expensive cousins. 

Amorphous/thin film solar panels
These thin-film solar panels are the least efficient on the market. Averaging just 7% efficiency, it’s easy to see why other cells are more popular. The upside, however, is their price.  They also work well in lower-light environments and can even generate power from moonlight. They’re easier to make than other cells and often mass-produced. This makes them an affordable option for anyone with enough roof space to warrant an installation. The other drawback is a shorter shelf life than their more rigid counterparts. 

Perovskite solar panels (an honourable mention)
Halide perovskites solar cells exist on the frontline of solar technology. We mention them here only as a matter of interest and cells to look out for in the future.  Studies suggest Perovskite cells operate at 25% efficiency, making them by far the most effective solar cells around. We have no idea how long these cells might last or how much they’ll cost when they do come to market. 

Although they’re not commercially available in the UK yet, many international companies offer kit versions. However, we advise extreme caution before considering such a venture.

Which are the best brands for solar panels?

In a recent survey by consumer mag Which, they asked 2000 of their readers to share their favourite solar panel brands. The survey looked at each panel’s warranty, maximum power output, and efficiency and this is how the top five compared.

	Warranty	Power Output	Maximum efficiency*
JA Solar	12 years	84.8%	565W at 21.9%
Jinko Solar	25 years	87.4%	445W at 22.27%
Longi	15 years	88.9%	585W at 22.6%
SolarEdge	25 years	84.8%	370W at 20.3%
Trina Solar	15 years	87.4%	450W at 22.5%

You can read the rest of their survey here. 

Solar Storage battery and making the most of solar power

Now we know all the factors that govern the energy solar panels produce in the UK, there is one more thing to consider. What happens when the sun goes down? 

It’s obvious that solar power comes from the sun. You’d be correct in assuming that in almost all scenarios you need sunlight for your solar system to function. So, how does your toaster work at night? The simple answer, as you’ve likely guessed, is batteries, or solar storage as they’re often called. 

The principle is as simple as it sounds. During the day, when we use less energy, but the sun’s rays shine brightest, the system collects more power. The electricity that you don't use at the point of generation can be diverted into your solar batteries or solar storage and saved for later. 

Like solar panels, there’s a huge range of solar storage options. These solutions range from simple DIY leisure batteries to cutting-edge lithium iron phosphate power banks with five-figure price tags.  At their core, they all work the same way, invertors convert the power from panels into energy that can be used in your home in the UK and store it in batteries for later use.  

We’ve covered the very basics, but If you’d like to know more about solar storage, please check out our in-depth solar storage guide. 

How to Tell How Much Electricity is Being Generated UK

When you go to have your solar panels installed, they will come with a meter that is placed in an accessible location within your home. What this meter does is record the amount of electricity that is being produced by the solar system, as well as how much electricity they are exporting back to the National Grid. This then allows you to work out how much you will be paid by Smart Export Guarantee (SEG).

Solar panel manufacturers are also starting to develop online apps for your smartphone that will allow you to access the performance levels of your solar panel. This can be done either via the app, or online from your computer. To get the most out of your solar panels and the electricity that is produced by them, you should ensure that you use your appliances (washing machine, dishwasher, vacuum, etc.) during the day as much as possible. This is because it is during the day that the panels will be generating energy.

You should also try to ensure that your home is as energy efficient as possible. This allows you to get the most out of your free energy. Try to use energy saving light bulbs, and don’t leave electronic devices on standby if you can help it, as these are all contributing factors to excessive energy consumption. Try, also, to only use the washing machine on a full load.

Of course, it can be easy to forget about our solar panels. They don’t require much maintenance (just an occasional wash), and they automatically power your home. However, make sure you check them over at least once a month to ensure they are working to the best of their ability, to provide you with the maximum solar panel kWh output.

Solar Panel Output, is it Worth it?

How much power a solar PV system generates depends on many factors. In this article, we've covered all of them. You should now have a good idea of what type and size of solar PV system you need to meet your demands in an efficient way. 

A well researched and sized solar panel system is clearly worth the investment for many homeowners in the UK. They reduce electricity bills, protect you from future price increase, reduce your reliance on the grid and, reduce your carbon footprint. Initial costs can be high, but tax breaks, the Smart Export Guarantee and long-term savings make them a wise investment.  

If you’re looking for a new solar system or any other type of renewable energy system we’d love to help. Reach out to us today and get the ball rolling. Or, if you still have questions, our site boasts a wealth of industry knowledge and honest, accurate advice on everything you need to know about achieving a brighter, greener future.

Want to Know More?

Have you found yourself interested in solar panels? If you're interested in booking in a quote then you can use our directory of renewable energy installation companies to find an approved installer in your area. Or simply give us a ring using the number at the top of this page and have a chat.