The Truth on Solar Panel Efficiency

by Solar Selections on October 3, 2011

Many of us spend a lot of time researching which solar panels we want to to invest in. There are a number of characteristics that we should be considering; however, the key indicator seems to be solar panel efficiency. It seems that the UK market has an obsession with panel efficiency and I just want us to ask ourselves why.

The Meaning of Solar Panel Efficiency

A happy 4kWp Solar Selections Customer A happy 4kWp Solar Selections customer

We all know that a solar pv panel comes with a specific efficiency rating, with the likes of Sanyo and Sunpower leading the way at approximatley 19% efficiency. However the majority of the products on the market are within the 13 – 15% efficiency bracket. So are the higher efficiency products superior?

The efficiency of a panel is simply how much of the solar radiation within a given area the solar pv panel can convert into useful energy. Therefore, in order for a less efficient panel to produce the same amount of power as a high efficiency panel it requires more roof area. Taking this into consideration, how much solar power will a high-efficiency 4kWp system (Sanyo) produce compared to a low-efficiency (Suntech) 4kWp system? They will produce the SAME amount of electricity! Yes, the less efficient system will need more roof space but the output should be almost identical. It is a little like the old saying: which is heavier, a ton of gold or a ton of feathers–a 4kWp is a 4kWp regardless of the panel efficiency. The efficiency of a solar panel only determines how much area is required for a given level of output.

Roof Space; High Efficiency vs Low Efficiency

We now need to address what the differences in required roof space are between the high and low efficiency products:

4kWp – Sanyo HIT 250W 18% efficiency (1.6m x 0.86m):

Number of panels required: 16
Total Output: 4kWp
Total Area Required: 22 square metres

4kWp – Suntech 190W 15% efficiency (1.58 x 0.8m):

Number of panels required: 21
Total Output: 3.99kWp
Total Area Required: 26.5 square metres

Overall difference: 26.5 – 22 = 4.5 square meters

As you can see the difference is not dramatic. If you have sufficient roof space, you need to ask yourself if it is worth the extra investment.

Have more questions about Solar Power? Contact us.

For further impartial information on solar panels and inverters, please feel free to get in touch with Solar Selections (

In addition, if you are looking for a free and informative solar quote comparison of up to 7 pv installers, simply fill out the “Request a Solar Quote Comparison” form to the right. Once completed you will instantly be emailed a quote comparison and your personal solar broker will be in touch to offer help if required.

Written by Tom Charlesworth

Phone: 020 7205 2267

© 2011 Solar Selections Pty Ltd

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