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I have an imminent installation of 9x410W on a West sloping roof, and 6x410W on the East sloping roof, but having checked the predicted output using PVGIS5 I have found the average December output is only 80 kWh, so only 2.8 kWh per day on average, and the Summer output is more than I can usefully utilise so much will be exported.

My thinking is to put 3 or 4 panels on the upper part of the South facing gable wall, with a predicted December output of 77 kWh (4 panels). It will then be a 3rd PV string so would need an additional inverter, but could be a basic single string inverter rated say 1.5 or 1.6 kW. The seasonal total PV output is then flattened off with a raised output in Winter, and lower in Summer, compared with the just West and East configuration.

The gable wall has just a first floor en-suite window (900H x 600W, roughly in the centre) and a ground floor kitchen door with a rain canopy above.
The next door house to the South has a single storey extension/garage and is approx 1m lower than my house, so the sun does catch the upper part of my gable wall all year round. Probably around 4.5 to 5 m from my gable wall to their full height gable wall.

Initial thoughts on potential issues are:-

1/ Planning permission. Is it different to sloping roof mount?
2/ Pigeon perch, and associated noise and fouling.
3/ Rain run off, and dripping to the walkway below.
4/ Ensure the inverter startup voltage is readily achieved if only 3 panels are used.

Has anyone experience of potential issues with vertical mounting on a gable wall?

Since you are normally limited to 3.68kW export, and I presume the main PV will be utilising that, will/have you get DNO permission to export more than 3.68kW or how wil you limit things?

You don't mention batteries at all, which means you might well be exporting more than you anticipate if you have to use the electricity whe it is produced.
Some (most?) hybrid inverters can take a pv input and batteries, but also I believe look at whether there is import/export on the mains and act accordingly. You would need to make a G99 or G99 fast track application to your DNO to use a hybrid inverter in addition to a normal one.

The already planned install includes a GivEnergy 5kW Gen2 hybrid inverter with 1 x 9.5 kWh battery, and has G99 approval for 5 kW export by the DNO.

I take your point though, in that a new application may be required.

Sim_C wrote: ↑Tue Oct 11, 2022 4:54 pm The already planned install includes a GivEnergy 5kW Gen2 hybrid inverter with 1 x 9.5 kWh battery, and has G99 approval for 5 kW export by the DNO.

I take your point though, in that a new application may be required.

If the panels get loaded onto the same inverter then you don't need another application assuming the inverter can take it. Or you DC couple them to the batteries via a charge controller, if that's possible with your system.

I have a couple of single panels on a wall or facade tied into existing strings via TIGOs (voltage optimisers) and that works for me. No planning permission required either as long as its no more than 200mm off the wall.

I took this photo on 25/11/2021 at 1330 GMT, so almost worst case shading from next door, which would be on 20/12/xxxx.

It looks like 4 panels would have to be 2+2 each side of the window, in landscape mode, as high as possible, but they would still get some shading in December.
With 3 panels in inverted 'V' shape, they could go higher up the wall, and possible avoid the shading.

I asked my installer about the pitfalls of mounting on vertical walls, and he advised the difficulty for him would be getting a commercially available mounting system that is officially rated/tested for the different loading on a vertical wall.
I guess he does not want any comeback on his company if a panel comes off in a strong wind and takes out the homeowner or a passer by.

Sim_C wrote: ↑Tue Oct 18, 2022 5:54 pm I asked my installer about the pitfalls of mounting on vertical walls, and he advised the difficulty for him would be getting a commercially available mounting system that is officially rated/tested for the different loading on a vertical wall.
I guess he does not want any comeback on his company if a panel comes off in a strong wind and takes out the homeowner or a passer by.

The panels I have on the wall have particularly strong frames, so I simply hang them off bolts like a picture frame. Then I use standard rails to simply secure them so they don't move. I have literally swung on them with my own weight and they aint coming off. But your right that there is not much call for commercial solutions and mine are also near the ground, so I just need a step ladder to deal with them.

I would caution having them on a gable end though, as they are particularly weak structures, especially the higher up the gable you go. Many fail in strong winds.
https://www.bbc.co.uk/news/uk-england-dorset-57253967

nowty wrote: ↑Tue Oct 18, 2022 6:13 pm I would caution having them on a gable end though, as they are particularly weak structures, especially the higher up the gable you go. Many fail in strong winds.
https://www.bbc.co.uk/news/uk-england-dorset-57253967

I'll second this. At our old house we struggled to get a TV signal (in the days of analogue TV). I made up some wall mount brackets to rawlbolt to just about the highest point of the gable and take the longest bit of 2 1/2" alloy tube I could buy (5m I think) to try and get the highest gain antenna I could find as high as possible. Barely lasted a month before it pulled the very top of the gable away, luckily without actually crashing to the ground.

When I got up there and replaced all the brickwork, I noticed that there were no ties between the inner block skin and the outer brick skin. I added ties when I rebuilt the gable, and also drilled right through the wall and fitted two vertical bits of 2" x 2" steel angle inside the gable, in the loft space, so the load was transferred into the block inner skin as well. I just used 12mm threaded bar to make the fixings through the two skins. Worked OK for a few years, until Freesat came along and I got rid of the long pole and fitted the dish on the same mounting.

Might be able to do something similar with some fail-safe mounting points for panels. Doesn't need to be every fixing, as long as there is something strong enough going right through the wall in the event of something failing.

Oldgreybeard wrote: ↑Tue Oct 18, 2022 6:25 pm

nowty wrote: ↑Tue Oct 18, 2022 6:13 pm I would caution having them on a gable end though, as they are particularly weak structures, especially the higher up the gable you go. Many fail in strong winds.
https://www.bbc.co.uk/news/uk-england-dorset-57253967

I'll second this. At our old house we struggled to get a TV signal (in the days of analogue TV). I made up some wall mount brackets to rawlbolt to just about the highest point of the gable and take the longest bit of 2 1/2" alloy tube I could buy (5m I think) to try and get the highest gain antenna I could find as high as possible. Barely lasted a month before it pulled the very top of the gable away, luckily without actually crashing to the ground.

Interesting...
A [road] engineer friend - who likes to be the centre of attention but I think is quite honest - told us a story about using the loo at a friend's house when he and his wife were having dinner there. He went to the loo which was upstairs against a gable wall and leant forward with his hand against the wall above the chinaware... to find that the wall fell away in front of him!
A

I'm glad I've seen the horror story posts before I ordered more panels and clambered up a ladder!
I might have to see if I can rig up some internal structure to distribute loading, luckily there's good access in my loft.

Has anyone any good tips on how to get a panel up to that height without scaffolding?