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How Efficient Are Solar Panels?

Solar cells have reached 47.1% efficiency in laboratory conditions

The most efficient solar panel material is monocrystalline

Many factors affect the efficiency of solar panels, including the weather

Solar panels are booming in the UK, millions of UK residents benefiting from lower energy costs, fewer emissions, and the ability to generate their own clean electricity. And with the cost of solar panels continuing to decrease, there’s never been a better time to get involved.

But are solar panels efficient enough to really lower – and potentially remove – our reliance on fossil fuels? We’ve done the research, investigating how efficient current solar panels are, what factors affect efficiency, and whether solar panel efficiency will improve in the future.

Man in yellow hard hat installing solar panels

What is the typical efficiency of solar panels?

Most solar panels on the market have an efficiency rating of 15-20% – but if you’re after a really efficient model, you can choose from multiple panels that top 22% efficiency. However, you should bear in mind that these are typically the most expensive solar panels on the market.

Solar panel efficiency is constantly being improved in laboratories, with some experimental panels reaching over 47% efficiency.

There are a few factors that affect how efficient residential solar panels can be, including the type of material they’re made from, local weather conditions, and how old the system is.

Why does solar panel efficiency matter?

Solar panel efficiency matters because the more efficient a solar panel is, the more of the sun’s energy it can convert into electricity.

So if a solar panel is 22% efficient, it means that it’ll convert 22% of the sun’s electricity into energy, with the remaining 78% being reflected back.

What are the main factors that affect solar panel efficiency?

Although most solar panels have an efficiency rating of 15-22%, there are a number of factors that can affect this rating. Check out the main factors that affect solar panel efficiency below.

Solar panel orientation

The direction a solar panel system is facing will determine the amount of light hitting it, which will either increase or decrease efficiency because it won’t be exposed to much solar energy.

If you live north of the equator, for example, you should place your solar panels facing south to generate the maximum amount of electricity.

Solar panel angle

Solar panels are most efficient when they’re angled between 20–50°. This is why solar panels on flat roofs are typically angled to absorb more sunlight.

Homeowners shouldn’t worry too much about their roof’s angle because mounting brackets can alter the panels’ placement and face them at different angles.


Shade can greatly impact the efficiency of solar panels because it limits the amount of sunlight hitting them and thus how much electricity they generate. You should factor this in when deciding where to place a solar system.

Even though south-facing roofs are the best orientation for solar panels, the efficiency rating will still drop if something is blocking the sunlight from the panels.

Type of solar panel

Different types of solar panels have different levels of efficiency, as does the material they’re made from. For residential solar panels, the three most common types are:

Monocrystalline solar panels

Monocrystalline solar panels get their name from the fact that they’re made from a single silicon crystal. Silicon is the material that most solar panels use to absorb sunlight and convert it into electricity.

This single-crystal silicon is formed into bars and cut into wafers, which are then connected to other single-crystal silicon wafers to make up an entire solar panel.

Of all the common types of solar panels, monocrystalline is the most efficient, and the most expensive.

Monocrystalline panels typically achieve an efficiency rating of 18–22%, and have an average lifespan of 25–40 years.

Polycrystalline solar panels

Polycrystalline solar panels are panels made from silicon crystals that have been melted down and poured into a square mould, which gives the panel its distinctive blue mosaic appearance.

They have a lower efficiency than monocrystalline panels — typically 13–16% — and are cheaper as a result.

Polycrystalline is also generally more eco-friendly than monocrystalline, as the production process wastes less silicon.

But a polycrystalline solar panel system won’t last as long as a monocrystalline one — 25–30 years, on average, compared to 25–40 for monocrystalline.

Want a more in-depth comparison? Head to our page: Monocrystalline vs Polycrystalline Solar Panels.

Thin film solar panels

Thin film solar panels are made by placing several thin layers of photovoltaic material (not exclusively silicon) on top of each other.

Their flexibility makes them ideal for curved surfaces, as you can mould thin film solar panels around shapes you otherwise couldn’t with monocrystalline or polycrystalline.

This flexibility does come at a cost of efficiency though — expect efficiency ratings of 7–13%, depending on the type of material used, and a lifespan of 10–20 years.

What impact does the weather have on solar panel efficiency?

Solar panels work best when they’re in bright, direct sunlight. This shouldn’t be surprising, but there are nuances that affect solar panel efficiency – even when the sun is shining clearly.

For example, solar panel efficiency actually starts to drop when the weather exceeds 25°C (77°F) because the electrons needed to generate electricity move around faster. This reduces the voltage and, subsequently, how much electricity the solar panels will produce.

Cloudy weather obviously impacts solar panels too. Thankfully, they’ll still work during cloudy days, just with a reduced efficiency rating — 23.8% for light clouds, falling to 66.8% during heavy cloud cover.

Solar panels can even work in hail and snow, which means those living in colder climates can still benefit from clean electricity. But bear in mind that you’ll need to remove snow buildup – any thicker than 5cm and your panels won’t be able to generate any electricity.

If you live in cloudy areas with snowy winters, you’ll fall back on the grid to power your home more often than people with solar panels in warmer, sunnier areas – unless you pair solar panels with another renewable energy source, such as a small wind turbine.

Do solar panels become less efficient over time?

Solar panels lose efficiency the older they get, producing less electricity as the years go on – at a rate of around 0.5% each year, according to the National Renewable Energy Laboratory.

This gradual decline in efficiency means solar panels have an average lifespan of around 30 years. But even after this point, solar panels will continue to work – just not as well.

This is why it’s usually worth considering replacing a solar panel system that is 30 years old or more. And if you have a thin film solar panel system, bear in mind that it should typically be replaced after 20 years or so.

But why do solar panels become less efficient over time? It’s typically down to three factors:


  • Light-induced degradation (LID): This is the process of solar panels being exposed to solar irradiation (radiation from the sun that degrades solar panels) and cannot be avoided
  • Potential induced degradation (PID): PID occurs when the solar panels’ voltage causes friction between the semiconductor material and other elements (such as the glass and the solar panel frame), which reduces efficiency over time. You can avoid this by purchasing high-quality solar panels from manufacturers registered with the MCS
  • Age-related degradation: The natural passing of time brings all sorts of things that can weather and degrade solar panels: heat, cold, rain, snow, hailstorms, you name it. That’s just part and parcel of what solar panels have to go through during their lifespan

How has solar panel efficiency developed over time?

Solar panels have come a long way since the very first photovoltaic panel was created in 1883, which had an efficiency rating of just 1%.

Jump forward to 2011 – just 12 years ago – and solar panel efficiency had increased to an average of 12%.

The methods for improving solar panel efficiency have continued to get better too. Now, you can easily purchase solar panels with 22% efficiency, and it won’t likely be long until even more efficiency is achieved.

What will solar panel efficiency look like in the future?

We’ve already seen a world-record solar cell efficiency of 47.1% reached by a team of researchers in 2019. Although this was under laboratory conditions, it’s still a huge milestone.

There’s also ongoing experimentation with different photovoltaic materials to achieve greater efficiency, such as perovskite – a material that, while more efficient than silicon, isn’t yet commercially viable.

However, one thing is for sure, we’ll probably never see solar panels with 100% efficiency because there’ll always be a portion of sunlight that gets reflected off of the surface. But with efficiency ratings improving as the years go by, solar panel owners should at least be able to harness more energy in the near future.


Solar panel efficiency is continuing to increase over time, allowing people to power their homes while using less space.

And despite having a maximum efficiency rating of 22% on the market, solar panels are still able to power almost any type of domestic property.

So are solar panels efficient enough? Yes, absolutely. Getting your own system will immediately start reducing your energy bills, shrinking your emissions, and making the planet a greener place to live.

Written by:
Tom Gill
Tom joined The Eco Experts over a year ago and has since covered the carbon footprint of the Roman Empire, profiled the world’s largest solar farms, and investigated what a 100% renewable UK would look like. Tom has a particular interest in the global energy market and how it works, including the ongoing semiconductor shortage, the future of hydrogen, and Cornwall's growing lithium industry.
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