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Discuss Solar PV Performance Comparison Tool/Calculator in the Solar PV Forum area at ElectriciansForums.net

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Leighton Gill

EF Member
Hi All,

I've been curious for a while as to how my Solar PV is doing compared to a 'typical' install.
Recently, I purchased a Smappee (which is darn useful), and I have also now joined pvoutput.org which is now building a clear picture around my generation and usage.
However, I wanted a simpler way of calculating how well (or bad) my Solar PV array has been doing since install, which was way back in 2011.

So, being a fan of MS Excel, I have created the attached spreadsheet to do the job for me.
Please note that I had to upload it in ZIP format, so you'll need to unpack it before using it.

It is a simple tool to use, all you need to know are the following details:

1. Your Solar PV array size (in KW)
2. Your orientation (Only does South or East/West at the moment)
3. Your installation date
4. Your latest PV generation meter reading.

Enter these into the spreadsheet and it will show you the following:

1. Your FIT Rate (in pence)
2. Your export rate (in pence)
3. The Current FIT rate
4. The current Export rate
5. Your average generation in Kwh per day
6. Your average £ earned per day (including export)
7. Your average £ earned per year (including export)

And also it will show you the comparison of your PV array compared to 'standard' UK solar generation figures. (I know these are going to be approximate, but you'll at least get a rough idea).

There's also a Chart at the bottom, showing you where you sit amongst the different types of PV arrays.

If you want to check where I'm getting the comparison data from, the second tab called "Data" has the data and the links included).

Feedback would be great on whether this is actually useful to anyone out there, but it's satisfied my own curiosity on how well my system is apparently performing.

Cheers,

Leighton
 

whinmoor

Electrician's Arms
Solar Guru
Hi,

Thanks for this. I’ve had a little play with it and can offer some thoughts:

1) Does it consider the annual inflation-linked increases? My own system started off at 43.3p in 2011 but will receive 50.67p from April 2016 – that’s if I’m reading the link below correctly

Feed-in Tariff (FIT): Tariff Table 1 April 2017 - https://www.ofgem.gov.uk/publications-and-updates/feed-tariff-fit-tariff-table-1-april-2017

2) Your “typical” figure is presumably based on “Middle England” and doesn’t factor in location or shading. I think the 3400 kWh p.a. for a 4kWp system is an under-estimate for a south-facing PV system with no shading.

3) If you’re really into this, you could ask for the purchase price and try to work out when the investment will pay for itself (break-even point). However, to be totally fair, you really need to calculate inflation and fuel price inflation. I'm not convinced that this is the best way to view a solar investment but some people might like it. The hardest part is calculating how much effect it has had on energy bills as maximising in-house consumption should be a priority.

4) I believe that the FiT rate from 01/04/17 til 30/06/17 will be 4.04p

I think it’s more useful to look at: PV potential estimation utility - http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Here you can input your precise location, orientation and tilt. You can see a monthly breakdown of output and compare against generation meter readings to see how your system is performing.

As an installer, I can cheat a bit because I can see the performance of plenty of systems we have installed in our local area so I can compare my own system against those!
 

Leighton Gill

EF Member
Hi Whinmoor,

Thanks for the detailed feedback, much appreciated. I've put my answers/comments in-line below:

1) Does it consider the annual inflation-linked increases? My own system started off at 43.3p in 2011 but will receive 50.67p from April 2016 – that’s if I’m reading the link below correctly
Good point, no it doesn't. I guess I can look at adding an 'inflation' table and/or doing the maths.

2) Your “typical” figure is presumably based on “Middle England” and doesn’t factor in location or shading. I think the 3400 kWh p.a. for a 4kWp system is an under-estimate for a south-facing PV system with no shading.
Exactly right, I chose "Middle England" figures to stay generic. I can add regions, and even shading with some additional data.
Regarding the 3,400kWh pa figure, that was showing the same across a few different 'typical' sources. Happy to increase it if you can point me at some different sources.

3) If you’re really into this, you could ask for the purchase price and try to work out when the investment will pay for itself (break-even point). However, to be totally fair, you really need to calculate inflation and fuel price inflation. I'm not convinced that this is the best way to view a solar investment but some people might like it. The hardest part is calculating how much effect it has had on energy bills as maximising in-house consumption should be a priority.
Yesm I did think of trying this, and even added a column to the 'Typical' array data in readiness. But as you say, I'd need to consider inflation. Although would I need fuel price inflation?

4) I believe that the FiT rate from 01/04/17 til 30/06/17 will be 4.04p
Ok, I'll go and re-check. I got the table for the FIT rates from another website, so it might be a mistake.

I think it’s more useful to look at: PV potential estimation utility - http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Here you can input your precise location, orientation and tilt. You can see a monthly breakdown of output and compare against generation meter readings to see how your system is performing.
This is great! Thanks for sharing. One of the main reasons I created the Spreadsheet was because I couldn't find anything else that would satisfy my curiosity!

So, not sure I need to do further updates to the spreadsheet, but if I do, I'll post the newer version on here :)
 
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