Solar PV Calculations

barrymung

I have a house with approx 16-18 sqm of roof, unshaded and south facing.

All the 'free' solar companies seem to want a roof about twice the size so I'm considering paying 2 having a system installed. I assume it'd be viable as I have seen a number of PV arrays installed on houses round this way that are smaller than the roof I have.

So..how do I calculate how much electricity a 16-18 sqm panel would produce? How much would it cost? How much feed-in tariff would I get? What grants are avaliable?

I suppose what I'm asking is whether there's a website with all this stuff listed so that I can do some calculations and see if this project is viable.

(Yes, I have googled)

Cardew

A typical output is 150Wp from a panel 1 square metre. So your roof would support a system of 2kWp to 2.5kWp.

If we take a 2kWp system, the cost would appear to be between £8,000 and £10,000.

The output depends where in UK you live. In Northern Scotland as low as 1,300kWh per year. Southern England as high as 2,000kWh per year.

Taking an average for central UK of 1,600kWh pa you would get £660 pa from FIT, £24 pa from selling electricity and what you could use in the house - say £40 to £80 pa.

I suggest you get some firm like Tesco to give you a quote, and the installer can give you a pretty accurate predicted figure of generated output.

zeupater

Hi

For calculations remember that you can't put the panels right up to the roof edges, so allow for a border of around 400mm-500mm all around the array and, depending on the mounting system, about 5mm to 10mm gap between panels ... a 17(ish)m2 (5(ish)m x 3.5(ish)m) roof suddenly becomes capable of only supporting 10m2 of panels, which would likely be around 8 x 175W panels (similar to .... (http://www.sharp.eu/cps/rde/xchg/eu/hs.xsl/-/html/product_details.htm?product=ND175E1F&cat=46005), so you'd likely be limited to something like a 1.4kWp system costing around £8K.

As the size of the system increases, the cost/Wp reduces significantly, hence with the rent-a-roof companies aiming at maximising their FiT income they're not at all interested in small systems ... or ones which either don't face close to south ... or have any form of shading ... or ....

HTH
Regards