How efficient are solar panels?

Measuring the efficiency of any renewable energy type can be a complex metric to understand; however, if you are considering installing solar panels then you might be trying to make an informed guess. 

Luckily, you don’t have to, because the team at BOXT have done the hard work for you. 

Here, we provide you with all the information on solar panel efficiency, how to best maintain their efficiency when installed and which panels are the most efficient. So read on and start your money saving, energy reducing journey today. 

How is solar panel efficiency calculated? 

Typically, the amount of sunlight that a solar panel converts into usable energy in relation to the total amount of sunlight that hits the panel, is used to determine the efficiency of each panel, and the overall system. 

A solar panel's energy output is measured watts (W) and, in order to calculate the efficiency, you will need to work out the following: 

• Solar panel output per day (measured in watts)
• Size of panel(s) in square metres x 1000
• Divide by 1000

It is important to keep in mind that it is not the same for every unit as each solar panel is unique. 

How efficient are solar panels, really?

The energy efficiency of solar panels differs from manufacturer to manufacturer and is dependent on a number of environmental factors, too. Whilst some manufacturers claim that their solar panels can reach up to 40-50% efficiency, the reality of this being achieved in practice is slim. What’s more, ultra-efficient solar panels typically aren’t the ones that are available for domestic use since they are incredibly expensive.

The majority of solar panels for homes will be between 15% and 20% efficient. This means that, on average, the solar panels on your roof or in your garden will convert 17.5% of the solar energy they capture into electrical energy.

Consequently, if the wattage rating is higher, the panels will generate more power. Depending on the size of the panel and how well they convert sunlight into energy, most residential solar panels have power output ratings between 250 and 400 watts.

What materials are solar panels made from?

There are four main types of solar panels, all of which perform slightly differently to each other. These are:

• Crystalline solar panels
• Monocrystalline solar panels
• PERC solar panels
• Polycrystalline solar panels 

Whilst crystalline and polycrystalline panels are more affordable, monocrystalline, and PERC solar panels are made of higher-grade silicon, meaning they perform more efficiently.

Despite being different to one another, most solar panels are constructed from these materials: 

• Sand: Most solar panels are made from silicon, which is the natural component in sand
• Ingots: Once collected, silicon is melted down at a very high temperature to form ingots in the shape of a cylinder
• Wafers: The silicon ingots are sliced into thin disks, known as wafers. It is named as such because they are usually as thin as a piece of paper
• Solar cells: Metal conductors are added to the surface of each wafer to give a grid-like matrix. Solar cells are then soldered together to create a panel 

What factors determine the efficiency of solar panels?

Photovoltaic (PV) cell efficiency and total panel efficiency are the two metrics that determine a solar panel’s efficiency rating. And, whilst you might think sunlight would be the driving factor that determines the efficiency and longevity of a solar panel, there are five other  elements that go into the equation, these are: 

1. Sunlight intensity

The strength of sunlight received has an impact on solar panel efficiency. When the sun is more intense and direct, more energy is produced for your home. Contrary to popular belief, solar panels can still operate in cloudy and overcast conditions. So, even if you live in the Outer Hebrides, you can still benefit from solar power!

2. Temperature

Solar panels are made up of hundreds of cells, and these are used to collect sunlight which then transforms into energy. As they are sensitive to temperature, excessive heat can reduce a solar panel's efficiency - so the warmer it gets, the quicker a solar panel's efficiency will decline over time. 

The term for this is temperature coefficient, and panels installed in warmer climates tend to have lower temperature coefficients. 

3. Material and technology

The different materials that make up each panel will have a direct impact on the efficiency of the overall system. Typically, solar panels are made from materials such as monocrystalline silicon, polycrystalline silicon, or thin-film solar cells, all of which have varied efficiencies. 

Generally, monocrystalline silicon offers higher efficiency compared to the other types of panels, but they are more expensive. 

4. Angle and orientation

For peak performance, you’ll want to consider the angle and orientation of where your solar panels are mounted, as this will impact their overall efficiency. Ideally, depending on the specific latitude of the installation location, you'll want your solar panels to be angled to capture the most sunlight during peak daylight hours.

However, you might need planning permission if you have a flat roof and want solar panels installed on it - read more in our blog.

5. Absorption and reflection 

Although solar panels are made to take in sunlight, some materials can reflect or absorb some of the incoming light, which lowers their efficiency. The panel's layout and any anti-reflective coatings that have been applied to the surface can reduce reflection and increase absorption.

Regardless of whether your solar panels are made from crystalline, monocrystalline, PERC or polycrystalline, you must take these aspects into consideration if you want to maximise their performance.

5 ways to maximise the energy efficiency of your solar panels

There are numerous ways you can get the most out of your solar panels. From storing energy to sending it back to the national grid, having efficient sources of renewable energy will cut electricity bills and reduce your carbon footprint. 

1. Regular cleaning and maintenance

Whilst solar panels are considered low maintenance, it is important to keep them clear of dirt, leaves, and other objects that could interfere with their performance, such as bird droppings. 

Take a look at our guide to pigeon-proofing solar panels for more information. 

Make sure you check the panels frequently for damage or other problems, and take proper care of them to ensure their efficiency and longevity. 

2. Using a high-quality inverter

You will need to install an inverter in order to use the energy generated from solar panels, as they produce direct current energy (DC), whereas most appliances in the home require alternating current energy (AC).

To minimise energy losses, look for inverters with excellent conversion efficiency.

3. Storing extra power 

Think about upgrading your solar panel setup with a battery storage system. You can do this to store extra energy produced throughout the day and use it when there is little or no sunlight.

4. Close monitoring

To monitor and control the operation of your solar panels, use an energy monitoring system. This can aid in identifying problems, help you understand your home's efficiency in more detail, and allow you to control your energy usage based on generated power.

Discover more about smart home technology in and what it is in our blog. 

5. Using high-quality solar panels

Simply, invest in solar panels of outstanding quality and efficiency. Even though they might cost more up front, over time they will perform better and provide more electricity during their lifespan.