How much energy do solar panels produce?

It’s widely known that solar panels generate electricity and reduce people’s reliance on the national grid, but how much electricity do they actually produce? Is it reasonable to expect solar panels to completely cover your electricity needs? 

In this article, we'll explore roughly how much electricity a solar panel system can produce, and explore the various factors that can influence solar output. 

If you’re interested in switching to solar, you can find out how much a solar & battery system could save you by answering a few quick questions below.

What’s the typical output of a solar panel system?

There isn’t really any ‘typical output’ of a solar panel system, simply because there are so many variables at play (more detail on this further down).

To give you a very rough idea: your solar & battery system could reduce your annual electricity bills by up to 103%. This is based on a household experiencing average UK irradiance with a 4.4kWp solar panel system and a 5.2kWh battery, using 3,500kWh of electricity each year and signed up to the Intelligent Octopus Flux export tariff.

But there is some significant variation here. Check out a few examples:

How much energy do solar panels produce per day?

A 4.3 kWp solar panel system will produce 10kWh per day in the UK, on average.

However, you shouldn't take this as a hard-and-fast rule, because your system's daily generation levels will depend on a host of factors.

As well as the variables listed above – like orientation, angle, shading, and inverter type – generation will also be affected by each panel's peak output, their location, the weather, and what time of year it is, as this will determine how many hours of daylight there are.

So on average, a 4.3 kWp solar panel system in London will produce 8.8 kWh per day, while the same system in Exeter will typically generate 12.8 kWh per day.

If it's in the ideal situation though, on a south-facing roof with an orientation of 40°, it'll produce even more solar electricity.

And wherever you are, your output will likely be around 55% below the average in winter, and 52% higher than average in summer.

As a result, you'll usually have to buy grid electricity during the colder months to make up the shortfall, but you can then sell your solar energy to the grid when summer comes round again.

How much energy do solar panels produce per hour?

Solar panels produce 0.4 kWh per hour on average, but this includes the hours after the sun goes down, when your system won't generate any energy.

Your solar panel system will be most productive at solar noon, when the sun is at its highest point in the sky. Due to the nature of the Earth's orbit, this time is almost never exactly 12pm, but instead occurs between 11:40am and 1:10pm, depending on the time of year.

You should therefore concentrate as much of your electricity consumption as possible during this time and the couple of hours either side, to take advantage of your increased solar output. Run the dishwasher, do the laundry, cook dinner – whatever makes sense for you.

Though of course, if you have a solar battery, you can simply store the extra electricity and use it later.

Solar panel output per m²

The average solar panel output per m² is 186 kWh per year.

Solar panels are usually around 2 m², which means the typical 430-watt model will produce 372 kWh across a year.

A solar panel system will need space on either side, so finding out your roof's area is only one part of working out how much solar electricity you can generate, but it's a great first step.

Solar panel output based on time of year

A solar panel system does not consistently produce the same quantity of electricity throughout the year. In the summer months when the sun is high in the sky (and the days are long), solar panels are at their most productive. And conversely, in the winter months when the sun is low in the sky (and the days are short), solar panel output drops quite significantly. 

For example, consider the below output chart, which is based on a four-bedroom home in Essex with a 6kWp solar panel system and 5kWh battery. The system generates almost 25kWh of electricity each day in May and July, but produces just 4.9kWh per day in December.

Solar panel output by season

What factors affect how much power solar panels can produce?

Solar panel power output depends on a wide range of factors, including:

• Solar panel power and efficiency
• Quality of installation
• Shading
• Solar panel cleanliness
• Solar panel degradation
• Inverters and optimisers
• Solar panel angle and direction
• Location in the UK
• Transformer losses

Let’s explore these factors in more detail.

Solar panel power and efficiency

When it comes to solar panels, 'power' refers to the maximum amount of electricity a panel can generate (in watts). The panel's 'efficiency' is all about how effectively it can convert daylight into electricity.

Higher power and efficiency mean greater electricity production. This means that, in the exact same conditions, a 430W solar panel with 22% efficiency could generate more electricity than a 350W solar panel with 20% efficiency.

Quality of installation

Solar panel systems are complex networks of electrical equipment that can underperform or malfunction if installed incorrectly.

If your installer doesn't secure the connections between the solar panels and inverter and the inverter and fuse box, your system may not convert DC electricity to AC electricity – which is the type your home runs on – or send all of the converted electricity to your home's devices.

And if they don't connect the diodes properly, your system could produce less solar electricity or be damaged by the battery discharging to the panels at night.

At best, bad connections will mean you get less solar electricity. At worst, a faulty connection can start a fire.

Shading

Shade can have a pretty significant impact on solar panel output, which is why it’s important to make sure there are no trees towering over your solar panel system. 

When solar panels are installed using a traditional string inverter, they’re connected in ‘strings’ (usually around 8-14 panels per string). If something is casting shade on one panel and reducing its output, this will have a detrimental effect on the electricity generation of the entire string.

This is where microinverters come in handy (more on that below).

Solar panel cleanliness

Solar panels all have a hydrophobic coating, meaning they are essentially self-cleaning. When rainwater lands on a solar panel it rolls right off it, in theory taking any dust or dirt with it. 

However, in certain areas, solar panels can accumulate enough grime that it limits the amount of daylight that can hit the panels.

This phenomenon, which is known as solar panel soiling, can be brought about by detritus as diverse as dust, exhaust fumes, agricultural emissions, and organic material like bird droppings, lichen, and pollen.

In the UK, solar panel soiling can cut your system's output by more than 5%, according to Loughborough University, but it's a far more serious issue in hot, arid areas like China, India, and the Middle East, where losses can reach 70%.

Keep an eye on your solar panels, and get them cleaned every time they get noticeably dirty.

If you would like to see the savings you could get from a solar & battery system, just answer a few quick questions below and we’ll provide an estimate.

Solar panel degradation

Like all electrical systems, solar panels degrade over time, which means they'll generate slightly less electricity as the years go by.

The average solar panel system in the UK loses between 1% and 3% in its first year, then 0.5% with each subsequent year.

That means after 25 years, the average system will produce 14% less energy than it did on its first day.

Degradation is more of an issue for solar panel systems in hotter climates, where the heat can negatively affect electrical networks.

Solar panel inverters and optimisers

As mentioned above, if one panel in a string inverter setup goes south, it messes up the whole string's output. With microinverters, each panel gets its own dedicated inverter and operates independently, so any malfunctions won't affect the entire system.

It’s also possible to stick to a normal string inverter and add optimisers, which are designed to improve the performance of the weakest panels in a system.

Your system's output could also be affected by solar inverter clipping, which is when your panels produce more electricity than your inverter's peak rating. As your inverter can't process the extra energy, it'll turn into heat and be lost to you.

Correctly sizing your inverters will avoid this happening too often, but don't spend too much in an effort to eradicate all clipping. In many cases, a small amount of clipping over the sunniest months is worth avoiding spending hundreds of pounds on more powerful inverters.

However, buying an efficient inverter is a good investment. Solar inverters are usually between 93% and 98% efficient at turning DC electricity into AC electricity, which is a large enough range to make a significant difference to your output.

Solar panel angle and direction

The angle and direction of solar panels has a big impact on their output. Aim for the sweet spot: facing south and tilted at an angle matching your latitude. The best angle for solar panels in the UK is around 20°-50°.

However, solar panels can still be very effective if they’re east-facing or west-facing – it’s just that south-facing is the optimum scenario. Any solar installer worth their salt will design a solar panel system for your property that makes the best use of your available roof space.

Whatever direction your solar panels face, some sunlight will reflect off them instead of being absorbed, reducing their output by around 2% to 4% – or it would, except more than 90% of commercial modules now come with anti-reflective coating.

The coating eliminates the great majority of this loss, so make sure it's included with any panels you buy.

Location in the UK

You won’t be surprised to read that sunshine makes a difference to solar panel output, and the UK sees a pretty wide range of solar irradiance. In the south of England there is an average of 128.4 watts per square metre (m²), whilst in the northwest of Scotland it’s just 71.8m².  

But despite the south coast of England seeing more sunshine than anywhere else in the UK, you can still have a productive solar panel system in any part of the country. Plentiful sunshine is a bonus, but not a key ingredient – and you can see from this list just how many other factors determine how well a solar panel system works.

Transformer losses

Your inverter will usually contain a transformer, which performs a vital function that does unfortunately result in some energy loss.

The transformer converts incoming DC electricity to AC electricity you can use in your home, and also changes the voltage of that energy to match that of the appliances your solar energy will then power.

Unfortunately, like all electrical products, it does produce a small loss in energy – about 1%, usually – because it involves multiple complicated processes.

Some inverters now come without transformers, which avoids this loss – but they're not common just yet.

How to get your solar panels to produce more energy

If you’re considering having a solar panel system installed, there are a few things you do in order to maximize its output. For example: 

1. Get high-quality solar panels
2. Hire a trustworthy installer
3. Maximise your roof space
4. Use microinverters
5. Monitor your solar panels

1. Get high-quality solar panels

A really obvious first step is to install premium solar panels on your roof. If you opt for panels that have an impressive efficiency rating and high power output then you’re already setting your system up for success. 

You should definitely go for monocrystalline solar panels instead of polycrystalline, as these usually perform a lot better.

2. Hire a trustworthy installer

Don’t skip on quality when you’re choosing which company does your installation. A highly qualified and professional installer will design a system that will get the best out of your roof, whereas cheap installers might not make the smartest decisions. 

You can also rely on a qualified installer to set up the solar panel system properly, meaning fewer issues further down the line.

3. Maximise your roof space

When you’re thinking about how many solar panels you need, there’s a strong argument for making maximum use of your roof space (budget-depending, of course). The more panels you can add to your roof, the more electricity you’ll be generating. 

Plus, if you expect your electricity consumption to increase in the future (maybe you’re going to get a heat pump, an EV, or start a family), then a larger solar panel system will be ready to support this.

4. Use microinverters

As mentioned earlier, standard string inverters mean that the underperformance of one solar panel can affect the overall output of a whole series of panels. Switch to microinverters and every solar panel will operate independently, meaning you don’t get situations where one panel is dragging the rest down.

Most trustworthy solar installers will let you know if microinverters are necessary, although they cost more than a normal string inverter. To learn more about the total price of going solar, check out our guide to solar panel costs.

5. Monitor your solar panels

The best way to ensure your solar panels are performing at their best is simply to keep an eye on them. Your system’s inverter tracks how much electricity your panels produce, and you can usually keep track of this on an app. If you spot a sudden unexplained drop in output, you know something is wrong. 

Sunsave’s first solar subscription, Sunsave Plus, comes with 20 years of remote monitoring assistance, meaning you’ll always have one of Sunsave’s solar experts keeping an eye on your system for you. And if something does go wrong, Sunsave Plus also includes 20 years of maintenance support.

Summary

The output from a solar panel depends on multiple factors like your location, your roof, and the quality of the system itself. A solar panel system has the potential to cover a huge chunk of your annual electricity needs, but there are many variables which can affect this. 

Ready to start your solar journey? Click the button below to find out how much money you could save with a solar & battery system. All we need is a few details and then we'll generate your savings estimate.

Solar panel output: FAQs