Solar PV Conflicting Quotes SE NW

onejump

I have had a number of quotes for solar I dont have a problem with prices or how it works. The thing is some are saying just have them on one roof whilst some say a split system would be best. The roofs in question are 130º SE and 300º NW on compass it says magnetic heading 210º. I have a shallow slope off only 25º. Who is right some guidance would be appreciated.

groovyf

I had a similar set of quotes just the previous month. One installer said don't bother with NE, just stick some (a small amount) on the SW. Whereas another said stick as many as you can on SW and the remainder on NE.
I think with some sound calculations, as well as advice from tunnel and Martyn1981 on here about checking out the PVGIS site: http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php# (stick in your post code, roof pitch, estimated size per roof and azimuths - note, they don't use 0-360 degrees of the compass), I decided to go with both panels on both roofs.
For the price I was quoted for just SW (6 panels), and the price of the quote for 6 on SW and 10 on NE, it worked out better to spend the extra and maximise the roof space available.

Martyn1981

Hiya onejump, and welcome.

It sort of depends on the size of your rooves. If you can get 3kWp+ on the SE, then it's probably not worth looking at the NW. But if say, 2.5kWp SE, then an extra 1.5kWp on the NW could well be worth it as the total cost per kWp drops as you add more panels.

This recent thread, pages 1 & 2 has lots of info on the economic arguments of 'going large' on less favourable rooves:

https://forums.moneysavingexpert.com/discussion/4909999

Mart.

onejump

Two answers two conflicting views not exactly what I was looking for. Can anyone give a sound explanation for either.

tunnel

Is there a reason you ask? ie, your roof is only small?

As Martyn says, if you only have a small roof then it may be worth considering putting panels on the other side as install costs are lower for bigger kWp.

If you have a large roof(SE) that can accomodate up to 4kWp of panels then its better to stick with that as going above that figure takes you into the 4-10kWp FiT rate which is lower.

It really does come down to your roof, so what is it?

Martyn1981

onejump wrote: »

Two answers two conflicting views not exactly what I was looking for. Can anyone give a sound explanation for either.

That's strange, as I'm in complete agreement with groovyf. The better orientation was small, so also using the less favourable roof worked in bringing down the total cost.

If you'd read the thread I linked, I think you'd have found the sound explanation you were looking for. You'd see that the first couple of kWp's cost the most (but you said you were ok with prices and how it works?) so going large helps to bring down the cost per kWp, so long as the lower generation available from the less favourable roof(s) is matched by proportional cost savings.

The explanations also go on to consider spread of generation, and time of day.

By 3kWp or more, you'll be getting better prices, and the amount that can go on the other roof(s) is getting too small >1kWp so probably/possibly not worth it.

Every job and every roof is different, without any details, I doubt any detailed explanation is possible.

So, give us a clue?

Mart.

Ageing_Stick_Insect

onejump,

The first thing I did was to post pictures of my roofs so the guys here could better understand my situation. Why not do that and it makes their lives easier. Use dropbox.com for the pictures.

onejump

Hope a goole earth snap is good enough.

hxxp://postimg.org/image/3rf1l8nvh/8820ab7b/
as a new user unable to post links
Another area of confusion 2 companies say they can fit 14 others say 12 the split system says the maximum is 8.

Ageing_Stick_Insect

Firstly, edit your link and replace xx with tt so it read http.

If the image you posted has north at the top then you have a 120 /300 (ESE / WNW) orientation. From my limited experience I would say you can mount panels on both but perhaps slightly more on the ESE roof as it's closer to south.

Use the PVGIS calculator to get an idea of how much panels on each roof will generate. http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php?lang=en&map=europe

Bear in mind the Azimuth you enter is degrees away from true south so WNW would be 120 and ESE would be -60.

tunnel

Hi OJ(simpson?:D)

There is no conflict, lets say you can get a minimum of 12 on the ESE, there's a panel called sunpower or benQ, both are the same and both are 327W making a combined 3.92kWp on your ESE roof.

If you wanted you could to keep costs down you could put 10 on the ESE and 6 on the WNW but use "standard" 250W panels with a dual string inverter.

You have plenty of choice, possibly even 12 panels either side but then you'd only be eligible for the 4-10kWp rate which is currently 13.5p(would also need DNO approval)

Don't be afraid of what the installers offer, just post the kit and cost they offer on here and someone will hopefully point you in the right direction.
I have both ESE and WNW and do quite nicely out of them(just under 6kWh on the WNW on its own today)

tunnel

Ageing_Stick_Insect wrote: »

Firstly, edit your link and replace xx with tt so it read http.

If the image you posted has north at the top then you have a 120 /300 (ESE / WNW) orientation. From my limited experience I would say you can mount panels on both but perhaps slightly more on the ESE roof as it's closer to south.

Use the PVGIS calculator to get an idea of how much panels on each roof will generate. http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php?lang=en&map=europe

Bear in mind the Azimuth you enter is degrees away from true south so WNW would be 120 and ESE would be -60.

Wow Ray, we created a monster:rotfl: