There is a question we hear often when people start looking into solar: are solar panels in the summer more efficient? It sounds like a straightforward question, and the answer is slightly more complicated than you might expect.
Yes, solar panels in the summer will generally produce more electricity than they do during the winter. However, it is not because solar panels like being hot. In fact, the opposite is true. Solar panels use light from the sun to generate electricity, not heat. So while a hot, sunny summer’s day might feel like the perfect conditions for solar, very high temperatures can actually cause a small reduction in the efficiency of the panels themselves. This is one of those areas where the words “efficiency” and “generation” can easily get mixed up. We think it is worth explaining the difference, because understanding how your solar system actually works is much more useful than simply assuming that more sunshine always means more efficient panels.
So, do solar panels generate more electricity in summer?
In most cases, yes. For us, this is the first myth worth clearing up.
The reason solar panels in the summer tend to generate more electricity is largely down to the amount and strength of sunlight available throughout the day. Summer brings longer daylight hours. The sun is generally higher in the sky, and there are more hours in which your panels can receive usable sunlight. That gives a solar PV system considerably more opportunity to generate electricity.
Think about the difference between a short winter day and a long summer day. Even if your panels were equally capable of generating electricity during both periods, the summer system has more daylight hours to work with. Add stronger sunlight into the equation and the overall amount of electricity generated can increase significantly. That is why, when we look at solar generation across the year, summer is typically one of the strongest periods for output. But this does not mean that summer heat makes solar panels perform better.
Myth 1: Solar panels need heat to work
This is probably one of the simplest misconceptions to address. Solar panels do not need hot weather to generate electricity. They need sunlight. The photovoltaic cells inside a solar panel respond to light and convert that energy into electrical power. The warmth that comes with sunny weather is not what makes the system generate electricity. In fact, if you have ever noticed that a bright but cool spring day can be excellent for solar generation, there is a good reason for it.
Solar cells generally perform better at lower temperatures. As the temperature of the cells rises, their electrical performance can reduce slightly. So, rather strangely, a cool, sunny day can provide very good conditions for the panels themselves. A hot, sunny day can still produce a huge amount of electricity because there is so much sunlight available, but the panels may be operating at a slightly lower efficiency because of the heat.
Generation and efficiency are not the same thing
If there is one thing we would like readers to take away from this blog post, it is this: generation and efficiency are two different measures. Efficiency is about how effectively the panel converts the sunlight it receives into electricity. Generation is about how much electricity the whole system actually produces over a period of time.
Imagine two days. On the first, it is bright, sunny and relatively cool. The panels may operate very efficiently. On the second, it is extremely sunny but also very hot. The panels may lose a small amount of efficiency because of their temperature. However, the second day could still produce more electricity overall because there are more hours of strong sunlight reaching the panels. This is why simply asking whether solar panels are “more efficient” in summer does not tell the whole story.
For most homeowners and businesses, what really matters is how much electricity the system generates, how much of that electricity can be used and how much electricity needs to be purchased from the grid.
Myth 2: The hotter the weather, the better the solar generation
It is an understandable assumption. We associate solar power with sunshine, sunshine with heat, and heat with summer. But the relationship is not quite that simple. Solar panels have what is known as a temperature coefficient. Put simply, this tells us how the electrical output of a panel changes as its temperature increases. As the panel gets hotter, its output can reduce slightly.
That does not mean a hot summer day is bad for solar. Far from it. The longer days and increased sunlight generally make summer an excellent time for solar generation. It simply means that temperature is one factor among many.
When we look at a solar installation, we therefore do not judge its potential based solely on how hot the weather might become. We consider the complete picture, including the panels themselves, their positioning, shading, ventilation, roof characteristics and the property’s electricity consumption.
What makes summer such a good season for solar?
The biggest advantage is really the amount of sunlight available. During the summer, the sun rises earlier and sets later, giving your system a much larger window to generate electricity. The sun is also generally higher in the sky, which can mean stronger and more direct sunlight reaching the panels.
A solar system is not just about how much electricity it can generate. It is about when that electricity is being generated and whether that timing matches the property’s energy use. For example, many homes and businesses use electricity during daylight hours for appliances, lighting, refrigeration, heating or cooling, equipment and other everyday activities. That means some of the electricity being generated by the panels can potentially be used there and then, reducing the amount of electricity that needs to be bought from the grid. This is one of the reasons we always encourage people to look beyond the headline figure for a solar system and consider how it will work in real life.
Myth 3: A cloudy summer means your solar panels are not working
Another misconception we regularly come across is that solar panels only work when the sky is completely clear. Thankfully, that is not the case.
Solar panels can still generate electricity on cloudy days because sunlight reaches them through the clouds. The amount of electricity generated will normally be lower than it would be on a bright, clear day, but the system does not simply switch off because clouds appear. This is particularly relevant in the UK, where our weather can change quickly.
We would never recommend judging the performance of a solar system based on one cloudy day, one exceptionally sunny day or even one particular week. Solar is a long-term investment, so performance needs to be considered over the course of the year.
What can affect solar generation during summer?
Although summer is generally a strong season for solar, there are several things that can affect how much electricity a system produces.
Shading is one of the biggest considerations. Trees, buildings, chimneys, roof structures, and other nearby objects can prevent sunlight from reaching parts of the array. Even partial shading can have an impact on generation, which is why we pay close attention to the surroundings when designing a solar installation.
Dirt and debris can also reduce the amount of light reaching the solar cells. Dust, pollen and bird mess can all accumulate on panels, particularly during dry periods. This is why regular cleaning of the panels should always be considered.
Then there is ventilation. Solar panels naturally get hot when exposed to strong sunlight. Having suitable airflow underneath the panels can help prevent unnecessary heat build-up.
The inverter is another important part of the system. It converts the electricity produced by the panels into electricity that can be used by the property. Like any electrical equipment, it needs to be appropriately specified, installed and monitored.
Does this mean winter solar is not worthwhile?
Absolutely not. This is another area where we think it is important to avoid an all-or-nothing view of solar.
Winter will generally produce less solar electricity than summer because there are fewer daylight hours and sunlight levels are lower. But the panels can still generate electricity. A solar PV system is designed to generate across the whole year, not just during the summer months. When we assess a system, we therefore look at expected annual generation rather than promising that every month will produce the same amount of electricity. There will be seasonal variation, which is completely normal. What matters is the overall performance of the system and how that generation fits into your energy needs.
Should you be worried about summer heat?
For a properly designed and installed solar system, we would not view summer heat as something to be worried about; it is simply one of the conditions that needs to be accounted for during the design process. The specification of the panels matters, including their temperature characteristics. So do the mounting arrangement, airflow, inverter positioning and the wider design of the system.
This is why choosing a solar installer based purely on the number of panels or their headline efficiency rating can be misleading. There is much more to a successful solar installation than the panel itself. We look at the property as a whole and consider how the system will perform in the real world.
The bigger picture: solar is about more than summer
When people ask us whether solar panels in the summer are more efficient, we understand where the question comes from. Summer is when we tend to see the strongest solar generation. There is more daylight, stronger sunlight and more opportunity for panels to produce electricity. But the important point is that the heat is not the reason. If anything, excessive heat can slightly reduce the efficiency of the panels.
The best solar system is one that has been properly designed around the property, the roof, the position of the panels, potential shading, expected annual generation and, perhaps most importantly, how the electricity will actually be used. And that is where we come in. We want people to feel informed before they decide on solar. We would much rather explain how a system works, including the things that may not sound quite as exciting, than leave someone with unrealistic expectations.
So, are solar panels more efficient in the summer? Not necessarily.
Do they generally generate more electricity in summer? Yes.
And is that mainly because there is more sunlight available over longer days, rather than because the panels are getting hotter? Exactly.
If you are considering solar for your business and want to understand what it could realistically do for you, we would be happy to help. We truly believe the best decisions come from having the right information first, so get in touch with our team to talk through your property, your energy use and whether solar could be a good fit. We can help you understand what to expect from your system throughout the year, including those brighter summer months, and answer any questions you may have along the way.
