How Effective Are Solar Panels in the UK?

Solar panels on UK homes can typically process around 10-20% of solar energy into usable energy. But depending on your solar panel’s materials, size and external weather conditions, this could increase to 25%.

Solar energy is an incredibly efficient way to create electricity, with no emissions or waste products created in the process. But how effective are solar panels in the UK and how do we measure their efficiency?

Keep reading to find out!

What is solar panel efficiency?

Solar panel efficiency is how much solar energy the panels can convert into usable electricity. This is measured in kWh (kilo-watt hours) per day.

Typically, a standard 2 kWp solar panel system will generate around 4 kWh of electricity per day in summer and 1-2 kWh of electricity in winter. This may not sound like a lot, but installing solar panels can enormously affect your energy bills and carbon footprint.

By installing solar panels, UK homes could save up to £610 a year on their energy bills. Better yet, UK homes with solar panels could get paid £110 a year from the Smart Export Guarantee (SEG).

How to work out solar panel efficiency

Solar panel efficiency is calculated by how well the solar panels capture and convert sunlight into usable energy in relation to its size.

To work out how efficient your solar panels are, you’ll need to know how many kWh of electricity they generate, the panel length and width (both in metres), and how much sunlight they receive.

However, it is important to note that solar panel efficiency is a matter of area, not power. For example, a 10% efficient 75W panel will produce the same amount of energy as a 20% efficient 75W panel. The only difference is that you should expect the 20% panel to be half the total size of the 10% panel.

The theoretical efficiency limit for solar panels is 33.7%. Labelled the Shockley-Queisser limit, this is a peak unheard of in domestic use and needs lab conditions to be met. However, your typical solar panel can reach a maximum efficiency of 25% in ideal conditions.

At midday near the equator, the sun generates 1kW (or 1000W) of sunlight per square metre. This decreases as you get further away from the equator, but these are the standard test conditions (STC) used to test every solar panel’s efficiency rating.

To calculate the efficiency of a solar panel you must:

Just remember to convert all dimensions into metres before calculating area as 1 square metre is not equal to 1000 square millimetres.

The equation looks like this:

What solar panel type is most efficient?

When installing solar panels, there’s no one-size fits all approach.

Your budget can have a massive effect on what type of solar panel you install on your property, but they all yield different results in their efficiency. So which is best?

Thin film solar panels:

UK homes on a budget should consider thin film solar panels as they are the most affordable, however, they are also the least effective.

Made from a substrate of plastic, glass or metal with one or more thin layers of photovoltaic materials, they can only convert around 10-12% of sun rays into usable electricity. Because they are so thin, they are more easily affected by weather conditions.

Polycrystalline solar panels:

Polycrystalline solar panels are more efficient than thin film solar panels but are still not the top of the chain

Also called multi-crystalline cells, they are made from multiple silicon crystals, giving them a more efficient conversion of solar energy. However, the spaces in between the silicon reduces the efficiency of the solar panel.

Monocrystalline solar panels:

Also known as single-crystalline cells, these are the most expensive option out of the three, but definitely the most efficient type of solar panel available on the market.

Monocrystalline solar panels are constructed from one piece of silicon, giving them an edge with how much energy they can capture.

What reduces solar efficiency?

The effectiveness of solar panels depends on how they are used and their surrounding environment. The following are some of the most common causes of a solar panel’s reduced efficiency:

  • Shading: Shading from trees, buildings or other objects around your home can massively affect how much solar energy your solar panels will capture. Some reports state constant shade can reduce efficiency by 50%.
  • Panel placement: In the UK, solar panels on south-facing roofs are the most effective and efficient as they capture the most amount of solar energy from the sun.
  • Roof pitch: In addition to the panel placement, how steep your roof is can also affect how efficient solar panels are. Find out more about the best position for solar panels in the UK in our blog post.
  • Maintenance: Although regular rainfall can clean solar panels, this is not always enough to maintain them. Dirt, dust and bird droppings that accumulate on the surface of your solar panel reduce its efficiency. Make sure to regularly clean your solar panels for the best performance
  • Temperature: While solar panels rely on the sun to create energy, they can actually get too hot and see a reduction in their efficiency as a result. On hot days, an increase of 10°C can reduce efficiency by 37%.

Is A Solar Battery Worth It?

Solar panels can only use up so much energy, and without a solar battery any excess energy is sent back to the National Grid.

By installing a solar battery to your solar PV system you could take one step closer to becoming energy independent. A solar battery can store excess energy generated during the day, meaning you can use it in the evening when your solar panels are not producing.

Additionally, with a solar battery installed you could potentially benefit from some of the additional government incentives, like the Smart Export Guarantee.

Find out more about how solar batteries work in our blog post!

Install Solar Panels For Free

Are you considering installing solar panels in your home?

You might be able to get them for free (or heavily discounted) through the ECO4 Scheme. The Energy Company Obligation (ECO) Scheme is a both government-funded initiatives that aim to improve the energy efficiency of homes across the UK.

And with there being 0% VAT on green energy until 2027, there has never been a better time to invest in solar panels!

To find out if you’re eligible for an energy saving scheme, complete our free online eligibility checker and we’ll help you to improve the energy efficiency of your home!

Save on energy bills.

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