How complicated is it to have solar panels installed on a garage / outbuilding?

[MrTWales]

This is my second post - the first was very useful, larely in terms of how to think about a battery. My conclusion is that it's not worth it for me, at least not for now.

 

I've been considering whether it's worth forgetting the main roof, possibly just for now, and having panels installed on an outbuilding. This is something like 20 feet by 15, fibreglass roof, sloped slightly (for drainage) towards south-west. It was built a couple of years ago to building regs standard I believe but it was not covered by builing regs as it's a permitted developement. They dug down a bit, so the heighest point of the roof from the outside is just over 2 metres so I don't think there are issues with it suddenly being too high and needing planning permission if panels are added (assuming the panels aren't too sloped, which I don't want as it would look silly).

 

There is an electric feed there from the outside box where the electric comes into the house and it has it's own fuse switch inside this box. In the room itself there is a small customer unit. It seems like a way easier install than having to get on the roof and I'm thinking that if I then wanted some on the roof at some point then it would always be something close to a seperate install anyway given they'd need scaffolding etc.

 

Am I correct in thinking that there would be forms etc needed, but the installer would / should sort that, and essentially the panels would to feed to a small-ish inverter (which I guess would have to be in the outside room) and then from there into the house vis this outside box? I assume that the supplier would need to be told (current Shelll as I got switched from a green supplier and I've not yet looked into switching)? It worries me a bit that this outside box (I don't know the technical name!) is kind of crammed inside as is due to the extra fuse for the outside room. 

 

Anyway, any comments would be great!

[Dillsue]

If its a flatish roof youll need mounts to angle the panels which have to be spaced out so they dont shade each other. Youll likely get fewer panels on the roof than if it were the same area on a pitched roof. Go to your local planning web site to find out if theres any planning restrictions

 

You dont need to tell your electric supplier youre fitting panels unless you want to claim SEG

 

Post a photo of the "outside box" and maybe we can work out what it is

[MrTWales]

Thanks. That outside box has the electricity metre in and I guess is just where the grid is connected. It's just a white electric box to me!

 

I guess I'm lucky in that the panels would go lenthways so the gaps wouldn't restrict quite as much as the other way around. I was thinking that you could fit three rows maybe. I did look at a chart that showed the optimal angle and direction and it looked like there wasn't all that much difference between something like 10 degrees and 30 degrees in terms of effectiveness. That may not be correct though, hopeful thinking maybe.

 

I'm in Wales and as far as I can see the only restriction that could potentially apply is that I couldn't go within 1 metre of an external boundary. 

 

If it's viable than I'll need to look into SEG and maybe other tarrifs if any vary with peak/off peak times. This is something I'm putting off until I know whether it's a go'er 😉 I guess there is also the option of some on the roof and some on the room.

[ProDave]

Assuming the garage has it's own consumer unit you connect the inverter to that.  You need a generation meter, AC isolator and DC isolator to connect it all up.  A picture of the meter box and consumer unit would be handy.

 

You don't need an MCS installer unless you want to claim the pittance of the SEG payment, you are better off aiming to self use as much as you can and forget that.  a picture of the roof would be good as well.

[Stones]

My system mounted to garage wall:

 

 

 

[MrTWales]

That looks great! I've never seen that angle of panels before.

[tonyshouse]

I think that you may well need planning permission for PV panels on a garage

[MrTWales]

Thanks. You may be right about the SEG stuff as I work from home so would probably use just about everything in the day, and could plan to use excess. 

 

One thing that has just occured to me is that I don't have a smart meter. My old distributor (sadly no longer around), Pure Planet, were going to install one but couldn't for some reason. They probably told me to contact the supplier but I never did as I wasn't all that bothered. Whether that's bad for getting solar or not I don't know. 

 

Anyway, it's dark but I took a few pictures!

[MrTWales]

I had a look around and don't think I need planning permission based on the gov.wales site.  Even with the extra height the build would still not hit the max height threshold.

[Dillsue]

12 hours ago, MrTWales said:

One thing that has just occured to me is that I don't have a smart meter. 

You dont need a smart meter unless you want to go for an MCS install and claim SEG export payments.

 

Your "outside box" is your meter box. If you want to connect your solar inverter to the consumer unit in the man cave, youll need a slightly larger one to install another MCB for the solar inverter to connect to.

[MrTWales]

Thanks. To be honest though, if I get solar then I think I'd like a smart meter as I'd like to know what is going on. I can't get my head around how it works when you have some solar but only enough to cover some things for some of the day. I assume that extra is needed is somehow drawn from the grid without you having to do anything as if by magic.

On 09/05/2022 at 10:20, Dillsue said:

You dont need a smart meter unless you want to go for an MCS install and claim SEG export payments.

 

Your "outside box" is your meter box. If you want to connect your solar inverter to the consumer unit in the man cave, youll need a slightly larger one to install another MCB for the solar inverter to connect to.

 

[Dillsue]

13 hours ago, MrTWales said:

Thanks. To be honest though, if I get solar then I think I'd like a smart meter as I'd like to know what is going on. I can't get my head around how it works when you have some solar but only enough to cover some things for some of the day. I assume that extra is needed is somehow drawn from the grid without you having to do anything as if by magic.

 

Pretty sure smart meters are free so no harm in asking for one to be fitted, if thats what you want. 

 

As you say, if your solar isnt generating enough power for what the house needs then any shortfall is drawn from the grid and your import meter records the top up youve taken.  Conversely, if your solar is generating more power than the house needs then any excess flows into the grid and if youve got a smart meter the export meter records the excess thats gone to the grid to power your local hospital/school/cannabis farm off green eleccy.

[SteamyTea]

1 hour ago, Dillsue said:

excess thats gone to the grid to power your local hospital/school/cannabis farm off green eleccy.

Thankfully I don't have PV, it would just be powering my neighbours 500 W external flood light.  Odd as she is in all day and night and never seems to notice it.

[MrTWales]

Honestly, this is so annoying. Just spoke to someone who said that the main house roof isn't really suitable due to the shape. They don't deal with flat roofs but he said that you always need planning permission (despite the low height) and there are likely issues with weight as the panels have to be weighed down as they can't attach them to the beams without risking leakage etc. Urghhh.

[Ronski]

I'm currently trying to clarify whether or not planning permission is required for a flat garage roof. Have emailed the council, but no reply yet. I think as long as they are not meet 200mm height on top of the roof then this is permitted development, but that would require the panels to be almost flat, which is not good.

 

You can now get through roof mounts, I don't have the link handy as I'm at work, they have a plate that screws to the existing structure, then a large piece of roofing membrane that's bonded to the mount, then once screwed down is then sealed the same way as your existing roof. This is what I'm looking to use, as I don't want loads of weight on our garage roof, the beams are not up to it.

 

Many roofing manufacturers now accept the above mounts, and they won't invalidate their roof guarantees.

[MrTWales]

That is very interesting. 

 

I've looked into this as well and the current rules really annoy me. We are trying to do the right thing here so why are the rules making it awkward? For example, surely if the build with the panels on still meets the permitted developement rules in terms of height then you shouldn't need permission? This is the case with me as the overall height would still be below the 2.5m limit.

 

What worries me is the text I saw that said "They should not be installed above the ridgeline" as this would always happen. It makes no sense imo for a flat roof but I think this is why the guy on the phone I spoke to believed that you essentially always need planning permission. Maybe the rules will change at some point though as it's nonsensical. 

 

The angle is intersting too as I don't think the efficiency loss is all that great if the angle is fairly flat (say 10 degrees or even less) and the upside is that you don't need as much seperation (as there is less shade) and the potential wind pressure is lower, so it may mean that you can fit more panels.

 

Another thing is that I think there is a rule, unless you get planning permission, that you can't go within 1 metre of the edge of the roof. Not sure why this is, maybe a wind thing, but I'd want to go closer to the edge (esp as the edges can take more weight) so that maybe requires planning permission anyway. It may be that this only means that you can't be within 1 metre of the edge of the property (?), so you'd be OK on an edge that faces your garden. Not sure!

 

My roof structure is pretty strong (I found a picture of a half built structure) but if you have a link to those roof mounts it would be interesting. 

 

[Ronski]

I'm still getting quotes, as I'd prefer an installed system, but that depends on how much the quotes come in at. One of the quotes I'm waiting on by Convert Energy seems very thorough, but he's said there is a mandatory 300mm setback between the panels and the limits of the building envelope. So rather than south facing he's going to quote on east/west, which means the panels can be fitted closer together, and thus use larger panels. So the actual estimated annual energy is actually slightly more than south facing with smaller panels 330 v 405w, the 405w would produce more south facing but won't allow for the 300mm around the outside.

 

These are the mounts I found, but couldn't find any prices online, they do different ones for different roof materials and cold roof/warm roof etc..

 

https://www.nicholsonsts.com/products/rooftrak

https://source.thenbs.com/category/uniclass/roof-anchors-for-solar-modules/wyCiF7pKPZkGMc1XvA1ejY/search-results/products?f=Category&v_1=Roof anchors for solar modules&score=0

 

Technically I'd argue that by definition a flat roof does not have a ridge line, I think you need to be within 200mm height to count as permitted development, put a parapet along the side that won't cause shading, and suddenly you have more height. If you put the panels at too shallow of an angle they won't self clean, and dirt and debris will build up, unfortunately I've no idea what that angle is.

 

[MrTWales]

I hope you are right about the ridgeline point.  I fired off an email to the council planning permission email yesterday but I'm not sure I'll get a reply. 

 

Not sure why you need 30cm from the edge. There must be a reason though. I guess it's not that much but it would be a miracle if you could use all the space with limited panel size options as you say.

 

Is the east/west thing as they want to fit rows along the long edge to minimise the gaps? In my case I'd want to line the panels along the longer edge so hopefully that helps, but I'm not finding it easy to even get quotes at the moment.

[Ronski]

The east west thing is to get bigger panels on, with the panels all facing south, you need spacing to stop one row shadowing the next, with east/ west think of a flattened upside down W, so you don't need space between the panels so they fit better in the limited space.

 

I actually like the appearance better as well, and another benefit is its easier to fit bird protection to stop those pesky pigeons nesting under there.

 

 

I think there's two possible reasons for the 300mm gap, one is access, the other could be related to wind, but the panels on my main roof are about 200mm from the edge, so I don't think everyone adheres to it.

 

I've had a hard time getting quotes as well, emails just deleted, silly prices, systems that don't do what I've asked them to quote for etc.

[MrTWales]

Just measured and, allowing for 30cm from the roof edges (not the wall edges as the roof extends a bit), I've got 6 meters by 5 meters. It seems like I could have 4 long rows of 3 panels potentially, which would be a decent size. No doubt there are a million reason why it won't happen though ... SIGH.

[MrTWales]

Thanks - love the diagram. Did they say how much space you need between panels? Can you tell me how big your roof is and what overall (theoretical) power the panels would amount to? You have 12 panels there which is what I was coming up with, but I'm just assuming that the gap doesn't have to be huge and I was looking at 169cm x 105cm panels. In theory, 12 of those panels is 4.5kw/h (though less for the angles etc). 

4 minutes ago, Ronski said:

The east west thing is to get bigger panels on, with the panels all facing south, you need spacing to stop one row shadowing the next, with east/ west think of a flattened upside down W, so you don't need space between the panels so they fit better in the limited space.

 

I actually like the appearance better as well, and another benefit is its easier to fit bird protection to stop those pesky pigeons nesting under there.

 

 

I think there's two possible reasons for the 300mm gap, one is access, the other could be related to wind, but the panels on my main roof are about 200mm from the edge, so I don't think everyone adheres to it.

 

I've had a hard time getting quotes as well, emails just deleted, silly prices, systems that don't do what I've asked them to quote for etc.

 

[MrTWales]

I'll just add that my cat walks over the roof a lot and no pigeon is going to go near the place so I guess that helps me!

[Ronski]

I have a thread here which detail some of what you ask

 

If the panels are all facing the same direction then panels shading panels will be an issue on your roof, it is on mine, mainly in the winter months though when the sun is low, even with the panels at a shallow angle. I modelled the garage/panels in Sketchup, and can then see how the shading is:

 

 

 

The above is at 13:30 on the 1 January, the shading only gets worse as the day goes on, and in winter you need every bit of sun you can capture, days are short, the suns low, and not very powerful. The panels are at 15 degree's, and they are 1722 x 1134.

[Ronski]

10 minutes ago, MrTWales said:

I'll just add that my cat walks over the roof a lot and no pigeon is going to go near the place so I guess that helps me!

 

Our cat would probably be scared of the pigeons! But there are plenty of others which aren't, but it was the main house roof that was the problem with pigeons.

Edited May 11, 2022 by Ronski
typo

[SteamyTea]

One of the problems with very shallow angles <15°, is dirt build up.

Rainwater just starts to stick to the modules.