SAP fail mainly due to walls

[pdf27]

7 hours ago, Iceverge said:

I'm a bit sceptical of build in panels. 

 

Will replacement parts of the same size be in available in 30 years or sooner if the panels fail? The more holes and fiddling and flashing you do with the roof the more likely it is to leak. Maybe not tomorrow but some day. 

 

With that in mind our PV is going on the garage and there's not a single penetration or hole in our hip roof. No lead no joints no nothing. Paranoid maybe!!  

PV panel failing ≠ roof leaking - it's a sheet of glass with a doped surface, and how often does one of those spring a leak. If the panel fails and you can't get a replacement, just disconnect it and keep running with the rest of the string.

[Iceverge]

1 hour ago, pdf27 said:

PV panel failing ≠ roof leaking - it's a sheet of glass with a doped surface, and how often does one of those spring a leak. If the panel fails and you can't get a replacement, just disconnect it and keep running with the rest of the string.

This is what I was thinking of.

 

I suspect you'd be unlucky to have it leak anytime in the near future but there are more areas of vulnerability than built on panels with a full roof covering below. They'll run more efficiently with ventilation behind and be easier to upgrade in future. 

 

Arguably less handsome however.   I don't know about the total installation cost comparison 

 

[pdf27]

2 hours ago, Iceverge said:

 

This is what I was thinking of.

 

I suspect you'd be unlucky to have it leak anytime in the near future but there are more areas of vulnerability than built on panels with a full roof covering below. They'll run more efficiently with ventilation behind and be easier to upgrade in future. 

 

Arguably less handsome however.   I don't know about the total installation cost comparison 

Not totally sure about that - with the GSE-type fittings any roof penetrations are inside the watertight layer, with conventional rack mounts they need to go through it. Ventilation isn't as good - so power is maybe 5% down - but it isn't totally non-existent and if you got for instance birds nesting under rack mount panels it might end up being quite close.

Costing is about £40-50 for ~1.7 m² of roof, depending on how much flashing you need. That's comparable to cheap tiles, more cost-effective than the nicer ones.

 

I'm figuring that upgrades are pretty unlikely over the life of the system - there are a few 50 year old panels out there still producing electricity, and the cost of scaffolding, etc. is pretty significant. So an upgrade of any sort only makes sense if the roof needs re-tiling anyway, and there is nothing in the GSE-style panels which looks like it won't last 50 or so years by which point the whole roof will probably need re-doing.

[pdf27]

Just looked up the numbers for a very big (18kW) PV array (split SE/NW) - Midsummer Wholesale is quoting just under £10k for all the bits, of which £6500 is the solar stuff and £3500 is the GSE bits. That's for 95m2 of roof, so £37/m². Switching to a rail-based system saves £1500, so the incremental cost of GSE over a conventional system is in the region of £15/m2 for a large installation, a bit more for a smaller system.

[Iceverge]

So roughly:

Built in is £105m2 + labour.

On Roof is £89/m2 + slates/tiles + labour. 

 

The difference sounds marginal.  

 

 

 

 

[pdf27]

7 hours ago, Iceverge said:

So roughly:

Built in is £105m2 + labour.

On Roof is £89/m2 + slates/tiles + labour. 

 

The difference sounds marginal.

All comes down to what you expect to pay for your tiles/slates. It's about break even for bog standard interlocking tiles, if you want slate or something a bit nicer it starts to get a little bit cheaper. It's certainly not a major cost saving, but I think it makes sense if you want PV and IMHO it certainly looks a lot better.