Hi, we put solar panels on our garage (4kw) and woodshed (1.8kw) roof for similar reasons to yours. We used roof integrated ones on the garage and I made the ones on the shed roof look integrated with raised battons and slates (see attached pic).

Our shed is partially shaded in winter, early spring and late autumn when the sun is low behind some trees, so we fitted Tigo Optimisers to each panel which stops one shaded panel from bringing down the output of all the others in the string. They can be used with pretty much any inverter.

We fitted 6 x 300w panels on our woodshed and these seem to be pretty cost effective (you can get higher wattage, but much more expensive). If you fitted 10 x 300w you'd get a 3kW array, which is a reasonable system.

In winter, our panels are completely in shade due to the low height of the sun, but on really bright days we still get a few hundred watts from ambient light.

Just to check though before you go down this route, have you made sure with the council that they won't allow solar panels under any circumstances? Ours refused us at first but changed their minds when I pointed out that they were roof integrated, black panels with black frames and didn't stand out at all.

Posted By: aclarkyI live in a conservation area and can't put solar PV on the roof.

I don't believe that's correct. e.g.:

https://www.quotatis.co.uk/advice/regulations/solar-panels/solar-panels-conservation-areas/

"Can I install solar panels in a conservation area?

"You can install solar panels in a conservation area. You can even do it without planning permission, but you do need to follow a number of rules. These include:

* "Not attaching solar panels to walls facing a road
* "Not installing stand alone solar panels in the area between your home and a road

"You’ll also need to follow the planning rules that apply to solar panel installations everywhere unless you want to make a planning permission application."

Posted By: aclarkythis is in Glasgow

Ah, Scotland is different and more awkward apparently.

https://www.gov.scot/publications/guidance-householder-permitted-development-rights-9781780456836/pages/6/

See §4.61 onwards, especially §4.70 "There are no Class 2B permitted development rights in a conservation area." and also the legislation under §4.73 "In the case of dwellinghouses in a conservation area or within the curtilage of a listed building , the floor area of the ancillary building can not exceed 4 square metres." That doesn't give much area for PV panels.

There was a whole series of cases some years ago in England where people fought councils to be allowed to put PV on properties in conservation areas. TL;DR they won and the law was subsequently changed. I have no idea whether there's any kind of equivalent situation in Scotland. Maybe some of our Scottish residents can help?

thanks guys, that explains why they said what they said.

I am just about to re-roof and as I am changing from scottish slate --> spanish I have to apply for planning anyway, I was going to try and tag a shed on the same application so it could be 3m x 4 or something.

So to think about repayment timescales - how many kwh could a solar array with say 8 panels produce if they are less than optimally sited - side of west elevation of house, some shading. Is it a waste of cash?

thanks again

without trying to be too accurate (since we don't have much control over the sun), you would be lucky to get 1500kWh/yr.

You might use 30% of that yourself, so say 400kWh/yr.
Assume 15p/kWh that you would not be paying for that 400kWh, so £60/yr (in reduced energy bill).

I think the export payment is around 5p/kWh if you're supplier is set up to do the export payments (or chnage to one who does), so that's 5p for 1100kWh/yr = £55/yr

So £120 saving per year. You can play about with amount of energy produced, used at home, etc, etc, but if you double, or half £120/yr, it's not lots of cash.

You'd maybe be looking at £3000 to get it installed and hooked up with tariff meter, so 20 yr pay back. That's still 5% return. If you've money resting idly in the bank at less than 1%, do it as a low risk investment, and because you're at least doing something to reduce your footprint, but it's not a big money earner.

You might consider a cheaper install, that doesn't include the export metering/payment, so not a registered installer with those additional costs, and just divert the excess power you don't consume in the house into your hot water cyl, via your immersion. Plenty here think that's un-green, but you're using solar energy to create hot water, and not importing elect or burning gas. Your gas will be about 5p /kWh, so you're no worse off financially for losing the export payments.

Alternatively, spend the money insulating your house, and reduce your footprint that way. If you're re-roofing, what are you doing about insulation in that part of the house (ceilings, coombes, draughty eaves)?? If you have traditional sarking boards (likely) and you fit the right roofing membrane below the slates, you can fully fill the rafters with insulation, and NOT require the 50mm ventilated void, and all the drafts and cold air washing that brings with it.

Personally I'd focus very hard on those opportunities, rather than taking the obvious route of consuming more earth's resources to have solar PV, and meanwhile leaking heat/energy from a new part of the house fabric...
...just some thoughts, not tablets of stone

Posted By: GreenPaddy

You might consider a cheaper install, that doesn't include the export metering/payment, so not a registered installer with those additional costs, and just divert the excess power you don't consume in the house into your hot water cyl, via your immersion. Plenty here think that's un-green, but you're using solar energy to create hot water, and not importing elect or burning gas.
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I dont think the objections to using a PV diverter for water heating are that its un green but more that its taking the pee out of the FIT system and "public" money. That veiw is based on the FIT recipient receiving payments for unmetered export units but grabbing all surplus energy for their own use rather than exporting a reasonable proportion in return for the payments received.

If youre not on the FIT system and not getting paid for deemed export, then grab as much PV as you want of your own generation. Only criticism that could attract is it may not be the most efficient use of energy??

god I love this forum! Thanks GP and WA. That sums it up for me, and interesting re investing in solar farms..

Yes there is lots of attention needed for insulation. The roofer is (happy) to remove sarking on the hard to reach areas in the roof and insulate - how sure are you I can fill the rafter with insulation? I'd love to but most people suggest the 50mm gap. And as it is room in roof the attic space is vented from the eves so if I blocked that off I would need tile vents in the attic space?

I had considered if it would be possible to create a warm roof entirely?? any thoughts or is that a condensation time bomb/ridiculous expense?

thanks again

Sounds like adding solar PV panels to your roof has been ruled out, and given the complex roof line I'd agree that it might have a negative impact on the visual appeal of the property (though this can be mitigated if you get roof integrated panels) and may not be cost effective.

However, your original idea of a DIY install on a shed roof, especially as it's such a large roof, could still be worth looking at, especially if you fit Tigo optimisers to reduce the impact of shading.