How efficient are solar panels? Everything you need to know
How well do solar panels generate electricity and can they produce enough to power your entire home? We investigate
Industry figures reveal that 1.3 million UK households now have solar panels installed, with more and more people turning to solar as an alternative to spiralling energy bills. But how effective and reliable are they as a source of power? In other words, how efficient are solar panels?
As a measure of how well solar panels can convert sunlight into usable electricity, a more efficient solar panel will generate more electricity than a less efficient unit when exposed to the same amount of sunlight. This is particularly important for homes with limited roof space, as well as those which don’t get much sunshine, in order to help you make the most of what light you can get.
In this article, we’ll examine the current efficiency of solar panels and explain what this might mean for you when choosing the best solar panels for your home. To compare quotes from reputable local installers, use our free quote-finding tool.
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What is solar panel efficiency?
All solar panels perform basically the same task: they capture the light from the sun and then convert that energy into electricity that can be used to power devices and appliances in the home.
Manufacturers are able to measure the efficiency of their solar panels as a percentage of the sun’s energy that a panel’s solar cells can convert to electricity, based on a set of standard test conditions. If a panel is 20% efficient, it means 20% of the energy in the sunlight reaching that solar panel is turned into usable electricity.
The more efficient your solar panels, the less reliant you’ll be on perfect conditions to generate electricity, and the fewer panels you might need.
This is the reason solar panel efficiency matters in the UK. Unlike in the Spanish countryside, for example, where you might have plenty of sunlight and roof space, in the UK, roof space and sunshine tend to be more limited. So you’ll want to look for more efficient panels that can generate decent amounts of electricity in less-than-perfect conditions, while also taking up less of your roof.
What makes one solar panel more efficient than another?
Solar panel efficiency is largely a result of the type and quality of a panel’s components. The three most common types of solar panels used for domestic purposes are monocrystalline, polycrystalline, and thin-film solar panels – of these three, monocrystalline panels are the most efficient.
Efficiency can also improved by using better-quality photovoltaic (PV) cells – also known as solar cells – in a more advanced cell configuration. The colour of the solar panel’s protective backsheet plays a role too. Since higher temperatures reduce efficiency, more heat-resistant colours, such as blue or green, are more effective than black, which absorbs heat – something you’ll quickly discover if you wear black from head to toe during a heatwave.
READ NEXT: How do solar panels work?
How efficient are solar panels in 2023?
The efficiency of solar panels has improved dramatically in recent years, from around 15% conversion of sunlight to usable energy, to around 20%. In fact, the current industry-average efficiency for a single residential solar PV panel is about 21%, with the top-performing units able to achieve up to 23%.
At present, most solar panels contain silicon-based cells, and these aren’t thought to be capable of exceeding around 23% efficiency, but as manufacturers explore the use of other materials, efficiency ratings are set to rise fast. A solar panel containing tandem cells made from silicon and the “wonder material” perovskite holds the world record for solar cell efficiency, clocked at a whopping 32.5%. This measure, recorded in December 2022, meant that nearly a third of solar light hitting the panel was able to be converted into usable electricity.
That record may soon be standard: Qcells has developed a tandem perovskite-silicon solar cell with a 29.3% efficiency and, in May 2023, the South Korean firm announced a $100 million investment into this technology, with a pilot production line planned for late next year.
Is solar panel efficiency the same as solar panel power?
No, but these measures are related. A solar panel’s rated wattage refers to the maximum amount of electricity it can produce under ideal conditions, known as “peak sun”. The power rating of a standard-sized panel has gone up, from 250 Watts a decade ago, to around 370W now.
However, a panel’s stated power rating only provides an indication of how much electricity it could potentially generate, dependent upon perfect conditions, while the efficiency rating tells you more about how well the panel will deliver in all conditions.
Are more efficient solar panels more expensive?
Yes, higher-efficiency monocrystalline panels are more expensive than less-efficient polycrystalline panels. But, since efficient panels produce more electricity than cheaper panels, over time they tend to be a better investment – especially since solar panel prices are falling, while the price of non-renewable energy remains very high.
Do solar panels lose efficiency over time?
Solar panels do degrade over time, gradually producing less electricity from the same amount of sunlight as the years go by. However, this degradation happens at a much slower rate than with most household appliances.
According to the National Renewable Energy Laboratory, solar panels and their output degrade at a rate of about 0.5% per year, adding up to a 5% drop in efficiency per decade. So, a 20-year-old panel will still produce around 90% of the electricity it was able to produce in its first year of life, and a typical solar panel will have a productive life of more than 30 years. Some panels now come with 40-year warranties – compare that with your boiler, which will probably need replacing after just 15 years.
What are the most efficient solar panels I can buy?
In our roundup of the best residential solar panels, we named the SunPower Maxeon 6 AC (pictured below) as the best solar panel for UK homes – in part because of its superb efficiency rating at just under 23%. So, even if you live in a tiny house with limited roof space, seasonal leaf fall, and regular cloud cover, SunPower’s lightweight panels adeptly convert the sun’s rays into electricity for your home. Their 2 x 1 metre panels cost £350 each, plus installation, provide up to 440W of power, and come with a 40-year warranty.
Other panels that impressed us with their efficiency were the relatively large Jinko Solar Tiger Neo 72HL4, with a 22.26% efficiency rating, and the smaller Qcells Q Peak Duo BLK ML-G9, with 21.4% and which we named the best solar panels for those living in a shady spot.
If you’ve decided that today’s solar panels are enough to meet your electricity needs, the next step is to get a few free quotes from local installers. Enter your details into our quote-finder tool, and our approved installers will be in touch.
