Solar PV cheaper than roof tiles?

[RedRhino]

Have other people run the numbers on PV vs roof tiles?

For new build you can put the solar panels directly onto the roof so removing the cost of the roof tiles that would otherwise be there. 

We have a quote for pitched roof tiles with membrane / battens / counter battens of £150 / m^2. 

A Jinko solar panel 1.086m x 1.726m = 1.87m^2 so its fitted cost with undertray etc is surely going to be a chunk cheaper. 

I don't think we will have additional costs from the inverter. 

And of course extra PV is useful if only to extend your season into the darker months. 
Anyone else come to the same conclusion? Anything I'm missing?

[ProDave]

What would bother me is the size of solar panels does not seem particularly standard, each time I have looked different sizes are being offered.

 

So you build your in roof PV with appropriate trays, say in 10 years time one or more gets broken, can you get replacements of the same size and appearance?

 

If I were doing this I think I would buy a number of spares and store them carefully for that eventuality.

 

And a good argument for doing as I have done and have some of your own scaffold.

[sgt_woulds]

I agree with ProDave.  It is certainly the case that installed PV panel prices are now at least comparable with roofing in concrete tiles and considerably cheaper than slate, but I too would be worried about future replacement. 

 

Correctly installed, it is rare for panels on a roof to suffer physical damage, (although with a greater frequency of more powerful storms and tornados, this is no longer a given) but electrically panels do go wrong.  More so I think with modern panels that, AFAIC, are not as robust as they used to be.

 

When I began installing PV panels 25+ years ago,  PV panels were bright cobalt blue polycrystal with spangly silver frames.  Power ranged from 65 to 175w. A typical example would be an Astropower AP-120, (roughly 700mm x 1500mm).

 

When Sanyo HIT panels came on the scene (starting with their 180w panels with the weird proprietary framing) and quickly progressing to 240w after about 4 years it forced other suppliers to up their game and with the introduction of FiT the market became flooded with 'all-black' monocrystaline panels all around the same wattage, (although nowhere near the same performance in real life). 

 

Average dimensions mid-tweenies were then about 850 x 1600mm.  Solar farms were not really a thing at this stage, so panel sizes were more to do with mono cell cutting and manual handling, which fitted well with UK roofs.  Smaller panels allow more flexibility in fitting, and the sizes then, (especially the early Sanyo panels) fitted well with the typical UK roof lengths.

 

Now PV panels are being optimised for large-scale solar farms using mechanical assistance for installation.  They don't fit UK roof sizes half as well, and finding new unused stock of older panels sizes is not easy.  

 

60 cell panels average 1000 x 1650mm (300 - 400 watts)

72 cell panels average 1000 x 2000mm (350 - 450 watts)

 

These newer panels seem to use thinner glass, back sheets and framing and consequently seem to suffer more from hailstorms and wind events.  I personally doubt that PV panels installed today will last as long as the old stock early 2000's panels I have on my garage.  (Including an unbranded 35w panel from the early 80's that still outputs 80+% of its original power).

 

 

I suppose the lesson is, don't expect panels to stay the same shape, colour, performance, (or quality).    I'd buy a stock of spare panels just in case.   

 

Also budget for at least 3 inverter replacements in 30 years of operation - modern electronic transformer inverters are nowhere near as robust, (or heavy!) as the old Iron core SMA and Sputnik of yore. 

 

On the plus side, you don't have to program them with country parameters using dodgy power line coms either - so some things have improved...

 

 

 

 

 

  

[Nickfromwales]

13 hours ago, sgt_woulds said:

These newer panels seem to use thinner glass, back sheets and framing and consequently seem to suffer more from hailstorms and wind events.  I personally doubt that PV panels installed today will last as long as the old stock early 2000's panels I have on my garage. 

Have a look at SolarWatt's glass/glass offering. I think there's YT footage of them being driven over by a transit van, and iirc then having golf balls fired at them at 80kph! 

 

The SolarWatt stuff have excellent performance and product warranties too, 30 years at 90% for the panels, and 12 years at 80% for the batteries. New stuff just been released, literally the paint is drying on the logos, and I saw it for the first time last Saturday at Farnborough HB&R show.

 

Warranties and guarantees all backed by a company that is basically BMW.

 

The biggest kick with warranties for solar, is that most offer long periods of cover, but if the installer goes bust your warranty goes with them. The other gotcha is that IF you get a replacement panel under warranty, you get exactly that....a panel delivered to your front door. Scaffold and fitting (including working out which one is duff) is down to you.

 

So, if you're going to fit some solar, and it is going to be a functioning part of the fabric of your build (on the roof as the rain-screen) then you'd want to fit the best panel by the most reputable supplier, so you don't ever have to climb back on the roof.

 

Some places it's fine to tighten the purse-strings, budgets aren't infinite by any stretch, but in some places it's best practice (IMHO) to pay a little more to get the best that's out there; providing it is not grotesquely over-priced for what it is, of course.

[Nickfromwales]

EDIT, it wasn't a transit van lol, of course, it was a BMW  

 

 

[G and J]

So, the panels I fit are part paid for by the saving in slates.  I fit optimisers that are accessible from inside the loft and I accept that some panels will die in the next 25years so the solar output will diminish, but not terribly, and the rest can keep going thanks to the optimisers.  I can live with that. I still get lots of kWh.  

[Alan Ambrose]

I have seen one supplier that does a 100% panel roof - no tiles at all. Looks great. But … does this not generally fall foul of the general installer guidelines? That is, are you expecting to have ‘tiles around the edges’?

[SteamyTea]

53 minutes ago, Alan Ambrose said:

fall foul of the general installer guidelines

Unless MI trumps it usually.

[G and J]

1 hour ago, Alan Ambrose said:

I have seen one supplier that does a 100% panel roof - no tiles at all. Looks great. But … does this not generally fall foul of the general installer guidelines? That is, are you expecting to have ‘tiles around the edges’?

I saw an ad for them.  Looked fab, PV one side, almost matching standing seem roof the other.  However, I looked at the gloss of the marketing, thought fondly of our budget and the fact that we want slates, and I didn’t save the details.  I categorised it as something for someone else’s grand design.

[Dillsue]

2 hours ago, Alan Ambrose said:

I have seen one supplier that does a 100% panel roof - no tiles at all. Looks great. But … does this not generally fall foul of the general installer guidelines? That is, are you expecting to have ‘tiles around the edges’?

I think the general guidelines are for on roof mounting where there's plenty of opportunity for the wind to get under the panels the nearer to the edge of the roof they are. If it's an in roof install then I guess its the detail of how the mounting trays are fixed on the edge of the roof??

[Alan Ambrose]

>>> If it's an in roof install then I guess its the detail of how the mounting trays are fixed on the edge of the roof??

 

Ah good point.

[Nickfromwales]

14 hours ago, G and J said:

So, the panels I fit are part paid for by the saving in slates.  I fit optimisers that are accessible from inside the loft and I accept that some panels will die in the next 25years so the solar output will diminish, but not terribly, and the rest can keep going thanks to the optimisers.  I can live with that. I still get lots of kWh.  

You’re no longer allowed to mount the optimisers remotely, I did this on a previous project, when it was ‘permissible’, but it was frowned upon by the solar company that I was instructing.

 

The optimisers are only needed if there’s split elevations on the same string, or shading. If you have optimisers it allows you to address each panel, so if a panel fails you can identify its location. 
 

If you got a solar PV panel such as the ones I mentioned above, then you’ll be at > 90% productivity in 30 years from now, guaranteed.
 

Why accept diminishing returns or possible early failure from buying cheaper Chinese stuff, even more so when you’re already saving on the slates etc??
 

Poor place to economise imho. 

[Alan Ambrose]

@sgt_woulds - thanks for your thoughts re panel sizes and suppliers. So, do you think we're trending to one panel size now, and, if so, what is it ?

[SteamyTea]

2 minutes ago, Alan Ambrose said:

do you think we're trending to one panel size now

I doubt it.  There are new chemistries coming on stream (Perovskite, Organic, Dye-Sensitive, Quantum Dot, CZTSSE) and new manufacturing processes (Printing, Vacuum Deposition) and design (Flexible, Irregular Shapes).

 

Probably the safest way to design is to pick the largest panel that is available and will fit, and hope that size will stay available for longer.

The problem with large panels on domestic properties is fitting, hoists and cranes may be needed because of HSE.

[Alan Ambrose]

>>> The problem with large panels on domestic properties is fitting, hoists and cranes may be needed because of HSE.

 

Maybe this is also limited, in practice, by the size of the largest trays.

[Dillsue]

2 hours ago, Nickfromwales said:

You’re no longer allowed to mount the optimisers remotely, I did this on a previous project, when it was ‘permissible’, but it was frowned upon by the solar company that I was instructing.

Is that a statutory requirement, manufacturer guidance or word on the street??

[Nickfromwales]

1 hour ago, Dillsue said:

Is that a statutory requirement, manufacturer guidance or word on the street??

When I contested it on another downstream project, because I like the idea of possible points of failure going where I can get at, I got a firm FO. Apparently MCS guidelines said (then?) that they now need to be with the panel with the factory leads from the optimiser attached directly, un-bastardized, vs connected via the 'extension leads' I had the fitters make up to set these in the attic plant space.

 

If I ask someone to MCS a solar PV install for me, I have to bow to their terms, so the next one had the optimisers under the panels. The fail sate with them is negligible anyhoo, so it's not like these things are dropping out 1 a year etc. 

 

You can 'address' the array with optimisers, so if one does snuff it you know exactly which panel its behind. 

[Nickfromwales]

7 hours ago, Alan Ambrose said:

>>> If it's an in roof install then I guess its the detail of how the mounting trays are fixed on the edge of the roof??

 

Ah good point.

If you click on a comment / post, then highlight it, an option to quote selection will pop up. Click on that and you're off to the races  

[LnP]

What are installers currently doing about fire risks for in-roof installations?

 

This guidance from the Fire Protection Association recommends (para 5.1.3):

 

New rooftop PV installations, including panels and fixing systems, shall not lower the fire performance/classification of the roof. In-roof systems should have the correct fire qualification to satisfy the requirements of the Building Regulations. If installation on a combustible or partly-combustible roof is unavoidable, then a fire resistant covering should be applied.

 

Perhaps sheathing the roof under the panels with cement board rather than OSB sarking?

[SteamyTea]

17 minutes ago, LnP said:

New rooftop PV installations, including panels and fixing systems, shall not lower the fire performance/classification of the roof. In-roof systems should have the correct fire qualification to satisfy the requirements of the Building Regulations. If installation on a combustible or partly-combustible roof is unavoidable, then a fire resistant covering should be applied.

Is that another example of my theory that for every rule or law we have that says we must do something, we have another one that says we must not do it.

Edited Tuesday at 21:12 by SteamyTea

[G and J]

1 hour ago, Nickfromwales said:

When I contested it on another downstream project, because I like the idea of possible points of failure going where I can get at, I got a firm FO. Apparently MCS guidelines said (then?) that they now need to be with the panel with the factory leads from the optimiser attached directly, un-bastardized, vs connected via the 'extension leads' I had the fitters make up to set these in the attic plant space.

 

If I ask someone to MCS a solar PV install for me, I have to bow to their terms, so the next one had the optimisers under the panels. The fail sate with them is negligible anyhoo, so it's not like these things are dropping out 1 a year etc. 

 

You can 'address' the array with optimisers, so if one does snuff it you know exactly which panel its behind. 

So it’s simply mcs rules.  Hmmmmm.

 

Taking the tails from the panels into the loft to allow reconfiguration to me seemed such a patently good idea, but I guess it allows users to meddle, perhaps the source of their rules.  The more I read about mcs the less enamoured I am.  The reactionary in me feels like spreadsheeting a diy instal and comparing the saving (and the little bit of engineering freedom) to the estimated export payments over, say, 15 years.  
 

Then I think about all the other things I’m going to try and do myself….  Sigh. 

[G and J]

Thinks…..  is there a solar pv equivalent to Cool Energy for heat pumps?

 

I buy the bits from them, get them installed, said company commissions and het presto, I’m mcs’d.  

[Nickfromwales]

1 hour ago, G and J said:

The more I read about mcs the less enamoured I am

But, without it people would be using cheap BZP fixings to hold solar panels, badly, to roofs. Because people like cheap short cuts. 
 

If one of those broke free and hit somebody you held dearly…. What then?
 

Then you’d be screaming “why isn’t this regulated?”  😌.

 

If your house burned down, because an optimiser set your attic on fire…..?

 

Regs are there to stop people doing things poorly, badly, or downright dangerously; this isn’t just to save them, but also to protect property and 3rd parties.

 

1 hour ago, G and J said:

The reactionary in me feels like spreadsheeting a diy instal and comparing the saving (and the little bit of engineering freedom) to the estimated export payments over, say, 15 years.  

That’s been done here numerous times Where have you been? lol   
 

40 minutes ago, G and J said:

I buy the bits from them, get them installed, said company commissions and hey presto, I’m mcs’d

Any mcs certified company would likely not appreciate you taking to meat off their bone, given their company running costs / overheads etc, and most would (should) refuse to do that.

 

Plenty of people out there who will do as you ask, they’re running the gauntlet unless they have evidence of every single thing you did from A-Z, including proof of fixings used etc. After it’s all installed, how the feck would they know?

[Nick Laslett]

15 hours ago, G and J said:

Thinks…..  is there a solar pv equivalent to Cool Energy for heat pumps?

 

I buy the bits from them, get them installed, said company commissions and het presto, I’m mcs’d.  

 
I bought my solar panels, GSE in roof trays and associated components from https://midsummerwholesale.co.uk

 

They have a web based tool called EasyPV that will tell you exactly all the components you need. Although I fitted my panels myself, I had already discussed with my electrician getting the MCS paperwork from him. 
 

I went with Enphase micro inverters. They may be a little more expensive, but they have many benefits, and are considerably safer, because each panel is electrically separate, whereas a string inverter all the panels are live, so there is a lot more volts. Remember a solar panel is essentially live as soon as it is receiving sunlight. 
 

The YouTube channel GaryDoesSolar was initially sceptical about micro inverters, but for some reason 6 months after his video dismissing them, he did a u-turn. This was long after I’d done my install, but here in the UK micro inverters do not seem very popular. 
 

 

 

 

[Dillsue]

18 hours ago, Nickfromwales said:

When I contested it on another downstream project, because I like the idea of possible points of failure going where I can get at, I got a firm FO. Apparently MCS guidelines said (then?) that they now need to be with the panel with the factory leads from the optimiser attached directly, un-bastardized, vs connected via the 'extension leads' I had the fitters make up to set these in the attic plant space.

So it's not a case of "you're not allowed" to install optimisers in the roof space, it's only an MCS requirement/guideline not to.