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Comparing the performance of solar PV panels

Posted by Gabriel Wondrausch on 5 September 2011 at 9:45 am

You wouldn’t buy a pair of shoes without trying them on in the shop first. They may look great on the model in the advert, but that doesn’t mean they’re going to be the perfect pair for you.

The same principle applies to solar panels.  Most of the panels and components that we use in the UK have been designed and tested in different parts of the world in very different conditions*.  So, until they’re fitted to your property you have no way of knowing if they’re going to work well on your property? Or do you?

Well, luckily, you do, and I’ll tell you why.

At SunGift Solar, in Exeter, we think it’s essential that we know which solar panels ‘fit’ best in this part of the world, so we built our own test array. Using this test array we can see how the individual panels actually perform in real life – in real time.

Our monitoring system allows us to monitor each panel individually and chart the different outputs of each panel. This means that we can give our customers the best possible service by offering them products that are not just tried and tested – but tried and tested in the climate in which they’ll be installed.

It also means that we can install, test and monitor all of the preferred solar PV panels and components on the market.  

Using the right equipment

Our test array uses Solar Edge technology, which allows us to use lots of different modules – a technology we are increasingly using on our customers’ installations. It would not have been possible to install the array using the more common method of having the panels connected in ‘series’ to one inverter, as the differing panel voltages would have caused problems.  

The Solar Edge system we use includes ‘optimisers’ that have been installed on each panel. This allows them to work independently from one another, optimises energy output, and enables us to monitor the performance of each module.  It then feeds back into a national-grid-connected central power box, which enables us to use an inverter and convert the DC voltage to AC voltage. This provides the highest conversion efficiency of greater than 97 per cent.

We fitted our test array in February 2011, and the results give us a clear picture of exactly what products will provide the best value for money for you if you’re thinking of fitting solar PV in this part of the country.

The test array consists of five different manufacturers’ PV ‘modules’ and gives location-specific results. The information from each solar panel is sent back to monitoring software, where our design team can assess their individual performance, see which ones generate the most electricity, and decide what product will do the best job for our customers.

Currently, we are testing the Siliken 245 Mono, REC 235PE, Sanyo HIT240, Conergy 225P, and Sharp NU185 modules, all of which are regarded as high quality systems with their own benefits. Our results show clear leads for both the Siliken and REC panels. This is quite an achievement, as they are currently the most cost-effective systems we install.

Manufactured in Spain, the Siliken 245 Monos may be the new kids on the block, but they have already won international acclaim for their high levels of efficiency and value. They won the 2010 Photon International tests, so we’re pleased to be one of the first UK installers to get our hands on them and check how they perform over here.

The REC 235PEs are also performing well, and we’re looking forward to testing the new REC 245 PE modules that are a top performing panel in leading industry tests. The test array has, in just under six months, generated a feed-in tariff revenue of £1,300. You can see a full comparison of all five systems in the results table above:

These results give us a great guideline as to how panels might perform best on a property in the Westcountry, or indeed the UK.

However, we’re also very aware that to be happy you want your shoes to fit you perfectly.  That’s why, despite the results you see in the table above, the best idea is always to get a renewable energy specialist in to take a look at your property. That way they can carry out a survey, analyse your situation, and advise you on the very best solution to suit your needs.

You can see total up-to the minute results from SunGift Solar’s test array in Nadderwater, Exeter by visiting the online monitoring page.

* Technical bit: the standard test conditions for PV modules are 1000 W per m² at 25˚C cell temperature. 

More information about PV panels from YouGen

Solar PV information page

Estimates of solar PV will improve with launch of new PV guide

Solar PV: Check whether it's suitable for your home

What types of solar PV panels are there?

Solar PV tiles: the pros and cons explained

Find a solar PV installer

About the author: Gabriel Wondrausch is founder and director of SunGift Solar, which installs solar thermal and other renewable energy systems in the South West of England.

If you have a question about anything in the above blog, please ask it in the comments section below.

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13 comments - read them below or add one


paul53Comment left on: 29 February 2016 at 4:36 pm


no  your  solar  meter  should never  go  backwards though  an old  grid  one will, i think you should give your  installer  a ring to  check everything is ok,this  week you should be  getting  at least  8  units  a day upwards depending  on your location  ect i  have  not  had  a  zero output day in  2  years.  there are  sites where you can  compare your  output  to  a similar set up as  yours ,one  is

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CarolineAnnComment left on: 29 February 2016 at 12:58 pm

I am new so sorry if adding in wrong place.  I has 16 panels installed 16.12.15 and I am having issues with the system. by day 70 they had only produced 97.37 units nad had not started on a minimumof 15 days.

The solar panel meter not the mains one has started to go backwards and my electricity bills have gone up.

Who can I ask if the above is normal?  Feeling very frustrated as the installer is not being very helpful.


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Confused Barry

Confused BarryComment left on: 22 October 2011 at 3:39 pm

Thanks Cathy for getting up so early to answer my question. I have today removed 2 soil pipe stacks from my roof at a cost of about £40 which has made a lot more roof available. I just had this nagging little doubt about the Poly type not being quite so good will let you know what I eventually go for!

Cheers Barry

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Cathy Debenham

Cathy DebenhamComment left on: 22 October 2011 at 3:59 am

Barry, click here to read a blog by Paul Hutchens which looks at the different types of panel. If you've got enough roof space, then polychrystalline should be fine, and cheaper.

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Confused Barry

Confused BarryComment left on: 21 October 2011 at 1:19 pm

 Please could you help me to resolve a question I have re Solar Panel types. I am about to place my order for a PV system. I have had 4 estimates and all ecept one have not mentioned the problem of installing 4kWp system with the local DNO. However, the one supplier that did tell me about this was not a "salesman" type but very honest and very practical person & local. The one problem I cannot come to terms with is the panels he provides are 240watt Viessmann (Germann) Poly Chrystalline. When I challenged him over this as all the reading up I had done said Mono Chrystalline were better. However, he was adament that the Poly type work much better in the cloudier conditions we ge get in this country. Could you please offer me some advise. I have one more quote to go from E-on on Tuesday who use Sanyo HIT N240SE10 so more confusion on the way!!

Thank You Barry.

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Gabriel Wondrausch

Gabriel Wondrausch from SunGift EnergyComment left on: 3 October 2011 at 5:22 am

Thank you for your comments.

There are some very good points raised, and I think it’s important to first address why we aren’t using ‘standard’ test conditions for our array.  There are already many highly-regarded tests run in these conditions (such as the Photon International test), which give comprehensive results.  However, our sole intention with the SunGift test array is to monitor how different systems perform in real-life conditions in the south west of England (where most of our customers are based).  This then enables us to make price/performance-related decisions with a better understanding of the facts, rather than simply relying on the standard information from manufacturers. We feel that it is a useful tool to be able to advise customers on their options.

In terms of the link, we’re sorry that it doesn’t seem to give all the information it should.  This is something we are working on and hope to have resolved soon.  Unfortunately, we will not be able to give full access to the suite, as this would allow access to change the parameters, but we should be able to give more details on the individual performance of the different modules.  In the meantime, we have formulated an up-to-date chart comparing the output of the panels which can be found here, and a couple of screen grabs showing the performance of the Solar Edge Panels: here and here

If you are interested in further details on our test array, please come and visit us at our offices in Exeter.

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Sunny Jim

Sunny JimComment left on: 26 September 2011 at 4:51 pm

As others have also commented, the links fail to provide access to the table that is supposed to support the claims in the text.  The Sheffield University solar farm trial gives detailed information on a much wider range of PV systems and has the advantage of not being in the business of selling anything.  By inviting micro-generators from all over the country to submit their readings it provides regular performance data in a wide variety of settings.

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newzealComment left on: 26 September 2011 at 4:31 pm

Can I see the online monitoring figures for each of the panels on your test array anywhere online? I went to the SolarEdge dashboard but could only find array totals. Thanks..

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sashtonComment left on: 26 September 2011 at 3:10 pm

This review seems a little simplistic. If one was to seriously compare panels one would want consideration of the behaviour of the panels over a temperature range (Monos generally behave worse at higher temperatures) possible consideration of colour temperature performance. No reference to sample sizes and possible variation of performance within samples. Finally, something that will concern many, as the panels are a long term commitment, how badly they degrade over time. I see many guarantees but I doubt many customers have access to reference test rigs to be able to substantiate a claim.

For those reasons alone I'm happy with my "poor performing" Sanyo HITs

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JWDComment left on: 26 September 2011 at 1:25 pm

I was dissappointed with the data available on this comparison which is a great idea - the graph at the top is too small to be useful and the link doesn't actually provide any panel type comparisons - is there not more useful data you could make available?

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kenwComment left on: 13 September 2011 at 3:06 pm

I recently installed Solar PV and during my selection process this was a big concern. How to find out if one panel make had an advantage over another. Also to consider is the visual appearance. Blue, black, frame style. I am happy with my final choice of Mitsubishi black MLT250 but it was not easy getting there. 

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raphComment left on: 5 September 2011 at 10:25 pm


I'm seriously considering having solar panels fitted and have had a few surveys carried out. All installers recommended different panels and claimed the one they recommended was best suited to my property.

Sungrid, Sanyo Hit, Sun station, Conergy, Solarcentury

I was beginning to believe the Sanyo was the best product but after reading your test results it seems I may be wrong.

Any advice would be very much appreciated asap. 

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chriswComment left on: 5 September 2011 at 9:27 pm

Sheffied University are also doing a study: The Sheffield Solar Farm

designed to measure the use of real world devices in Northerly locations.

If you have solar PV installed you can "donate" your data to help them

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