The most efficient solar panels in the world are capable of 40 to 50% efficiency. However these are beyond the budget of homeowners looking to achieve a healthy return on investment.

To achieve the best return on your investment you should opt for a solar panel that offers a balance between cost and efficiency.

To compare efficiencies and prices of pv panels offered by installers operating in your area, fill in the form at the top of the page.

How efficient are solar panels?

Most domestic solar panels have an efficiency of around 10% to 20%. More efficient solar panels are available, although these tend to be beyond the requirement and budget of most residential installs.

When deciding the best solar panels for your circumstances, you will want to look at which solar panel will give the best return on investment rather than just simply the most efficient solar panel.

Higher efficiency solar panels tend to cost more, so a less efficient but cheaper solar panel is likely to deliver a higher return on your investment. Less efficient solar panels will need a larger space on your roof to produce the same amount of electricity as a more efficient panel.

You might still want to consider a higher efficiency panel if you have a particularly small roof or your roof only has a small area out of permanent shading.

You can enter your postcode in the form at the top of this page to compare prices from installers operating in your area. These installers will be able to advise you further on the best solution for your particular requirements.

Most Efficient Solar Panels

As we explained in the section above, you shouldn’t just choose the most powerful solar panel. However, to give you an idea of the most efficient solar panels offered by leading brands, we have compiled the table below:

The table below shows the efficiency of popular, but less efficient solar panels which, provided you have suitable roof space, often deliver a higher return on investment than the most efficient solar panels on the market:

Click here to read about the best solar panels

Five tips to improve efficiency

As the video explains, there are 5 factors which can affect the efficiency of your solar panel system:

1. Direction and angle of your roof
Your roof will usually need to be South, East or West facing and angled between 10 and 60 degrees to work at its peak efficiency.

2. Shade
The less shade the better. Your solar panels will have a lower efficiency if they are in the shade for significant periods during the day.

3. Temperature
Solar panel systems need to be installed a few inches above the roof in order to allow enough airflow to cool them down. But this is less important in the UK climate, so it works to our advantage.

4. Time of year
Solar panels work well all year round but will produce more energy during summer months when the sun is out for longer.

5. Size of system
Typical residential solar panel systems range from 2kW to 4kW. The bigger the system the more power you will be able to produce. Learn more about what size would suit you

Click here to learn more about how much electricity solar panels produce

How is Solar Panel Efficiency Measured?

This is a bit of basic maths - the ratio of incoming sunlight to power out of the panel, expressed as a percentage. So if you have 100 watts of sunlight reaching a panel and you get 10 watts of power out, that's 10% efficiency. There are two types of panel - photovoltaic (PV) panels, which generate electricity, and thermal panels, which use sunlight to heat water. PV efficiency is typically 10-20%, while thermal panels can offer 90% efficiency, but they won't power your lights, only heat your home and give you a hot shower and offer none of the feed-in tariff earning potential of PV panels. Most consumers are interested in the range of PV panel efficiencies that are possible.

Other Factors to Consider

A manufacturer will provide a figure for the efficiency of its panels. This is usually a lab-based assessment, sometimes described as a label rating, a bit like the miles per gallon figure a car maker supplies, i.e. it is a reflection of what's possible only under ideal lab conditions. Some panel makers may provide an in-situ efficiency rating for what's possible on a typical installation, called the PTC (Performance Test Conditions) rating. Clearly this rating is a better guide to what you can expect in practice.

Best of all is a 'system PTC rating', which includes not only the panel efficiency, but also that of the inverter, the device which converts the electrical output from the panel from direct current into alternating current for domestic use. Inverter efficiencies range from around 85% to 95%.

Types of PV Panel and their Efficiencies

The two main panel types are monocrystalline and polycrystalline silicon. Monocrystalline costs more to make but efficiency is higher, typically 13-17%. So you can in theory get more power out per unit of surface area. This might be a consideration where roof space is limited and could mean buying less panels to meet your needs.

Polycrystalline units are cheaper to make, but have lower efficiency, usually 11-15%. A third system combines one of these two panel types with a thin-film PV system, again more expensive, but capable of efficiencies exceeding 17%.

Next Steps

You can join the thousands of homeowners in the UK who have used The Eco Experts to compare prices of MCS accredited solar installers operating in their area. By comparing the prices of up to four local installers, you can save up to 60% on the cost of installing solar panels. To compare prices now, simply enter your postcode in the form at the top of this page.

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