Quotes and install questions

Martyn1981 · 2 July 2018 at 6:10PM

Hiya, your FiT is based on the Wp of the panels, so it would be 5.4kWp, putting you in the first bracket 0-10kWp.

The benefit to you however, is that you wouldn't need to worry about the DNO, as you can fit a system that can't exceed 3.68kW without prior permission. So a suitably sized inverter, capped at 3.68kW would work well in that example.

Zarch · 3 August 2018 at 9:47AM

So its been a while..... i've been digging, learning, taking it all in. Hopefully I know all I need to know now.

Of the two installers I had quotes from one has gone quiet and as now left me currently with one viable set of quotes. That is CTS Renewables in Mansfield. They came with a personal recommendation from a regular on here and all through discussions they've been really good.

We've come to the conclusion that I get can 17 panels across 4 different roof; 8 on Main front (SW), 2 on front Porch (SW), 4 on Dormer (SW/flat) and 3 on rear extension (E-ish).

Here are the quotes. This is for full Solar Edge on every panel and a 5000 HD inverter.

17 x 300w (Perlight), 5.1kWh, £6462, so £1.26 per kWh
17 x 320w (LG), 5.44kWh, £7131, so £1.31 per kWh.

Both will pay for themselves in about 9 years (both their figures and my figures)

So whilst the 300w offer better 'value' (£ per kWh), I think that the 320w panels make sense in the long run. I will get the extra £700 back in the long run in FIT alone. And the extra 300w could be vital through the leaner months?

I'm hoping now to get things moving so I can get installed before end of September and the next quarterly drop in FIT.

But the current problem is that the flat roof on the dormer needs replacing. Its a fibreglass jobby that is flaking. There is no way i'm going to put solar panels on a roof for 20 years without it being capable of out lasting the panels. So got to get that repaired/fixed before I can get the Solar.

CTS have applied for the DNO application for me. But have said this could take up to 45 days with Northern Power.

Any thoughts on the above. Does it sound all ok? Any questions? Any stand out issues?

Thoughts and wisdom from the group would be appreciated.

Ta. :beer:

Martyn1981 · 3 August 2018 at 12:49PM

My gut feeling is that that extra 5p/Wp is worth it for the extra gen. When gen is low in the winter, you'll be back to agree ..... I hope.

Price wise that looks really good I think given the high panel efficiencies, multi-rooves and SolarEdge. Again my gut feeling letting older posts and prices over the years stir and swim around in my head.

pinnks · 3 August 2018 at 12:53PM

Others will have thoughts on the overall price but may I question your logic/maths on the 300W? Please read what follows in the context of me being an advocate of going large!

Depending on where you live, orientation etc etc you may get about 1,000 kWh per year for each 1,000 Wp of panels on your roof. I have 3,500Wp in my larger west-facing system and get about 2,800kWh per year. I have 5,250Wp overall and get about 4,500kWh overall. So, nowhere near that theoretical sum.

Let's work on the one to one assumption as it makes the maths easier. 300 extra Wp would generate 300 extra kWh per year. Let's assume FiT/export of 5p per kWh (I think it will be a little higher but near enough), that would give you an extra £15 per year for a £700 investment.

If you used 100% of that extra generation (not going to happen absent batteries) you would save about £45 in addition. In winter you would benefit from the extra panels but not to the tune of max production (1000kWh per year per 1000Wp) because it is, well, dark for most of the day.

So, of your theoretical extra £45 production/own consumption you might get perhaps £10? Let's say it's £15 to make us feel better. This would mean you save or receive £30 per year for your £700 investment. Pretty much 20 years to recoup even taking inflation into account.

So, if the decision to go for that system is based on green, max out roof and not too worried about return on investment then go all out but if the return is important the extra £700 may be an expense too far.:beer:

Coastalwatch · 3 August 2018 at 1:30PM

Zarch wrote: »

So its been a while..... i've been digging, learning, taking it all in. Hopefully I know all I need to know now.

Thoughts and wisdom from the group would be appreciated.

Ta. :beer:

Hi Zarch, considering you have four separate arrays and with Solaredge included the prices quoted seem reasonable to me. I appreciate your frustration over the delay with a DNO application but as Mart suggested by capping the output to 3.68 kW the DNO's permission would not be necessary. This may appear to limit the arrays output although in reality I suspect by very little and only at peak output times also. For instance the total output maybe 5.44 or 5.1 kWp but with four arrays and a dormer window then some shading seems likely to come into play plus the sun cannot shine at it's optimum from the east and south west at the same time. Not sure if your panels on flat roofs will be laid flat or tilted! So taking the three east panels out of the total for a moment then 14 x 320 = 4.48 kWp. Taking losses into account of say 14% brings this figure down to 3.852 kW. While this figure maybe achieved with the sun in the SW quadrant the east panels will not be producing to max. According to Solaredge data sheet the SE3680H unit would accommodate a maximum DC input of 5700 W. Taking this route would alleviate the DNO issue, although others on here or your installer might suggest otherwise or opt for the SE4000H unit.

Our 8.85 kWp installation is in two sections, 90 degrees apart, for which we have a single SE6000H Inverter in situ. We did extend the Inverter warranty out from twelve to twenty years for around £180.
Hope this helps.

Zarch · 3 August 2018 at 5:04PM

Thanks chaps, will disgest and reply fully later.

For now, the PVGIS on both systems is

17 x 300w (Perlight), 5.1kWh, £6462, so £1.26 per kWh; 4483
17 x 320w (LG), 5.44kWh, £7131, so £1.31 per kWh; 4769

So 286 for that extra 17 x 20w.

The dormer panels would lay at 15 degrees on these:
http://www.pluginsolar.co.uk/?product=renusol-console-5200-tubs-for-ground-or-flat-roof-mount

pinnks · 3 August 2018 at 5:09PM

So, 286kWh expected increase in generation each year, so still about £15 extra FiT and £15 extra own consumption savings equals £30 more return each year, for a spend of £700. I think I know what I would do - haggle or ditch the more expensive one:beer:

Martyn1981 · 3 August 2018 at 5:56PM

Zarch wrote: »

Thanks chaps, will disgest and reply fully later.

For now, the PVGIS on both systems is

17 x 300w (Perlight), 5.1kWh, £6462, so £1.26 per kWh; 4483
17 x 320w (LG), 5.44kWh, £7131, so £1.31 per kWh; 4769

So 286 for that extra 17 x 20w.

The dormer panels would lay at 15 degrees on these:
http://www.pluginsolar.co.uk/?product=renusol-console-5200-tubs-for-ground-or-flat-roof-mount

This is really interesting in a weird way, because I agree completely with what pinnks is saying, yet I'd go with the bigger system.

I can't understand why, and certainly, therefore, can't explain nor justify it. Weird.

So approx 6% more gen for approx 10% more money, and of course, as you go bigger and bigger you will use less and less of the extra ......... but I'd still go for it.

Perhaps it's the end of FiTs, perhaps the justification is get as much as you can first time out as messing about later costs more, or perhaps £700 just doesn't worry me that much, anymore, in this context.

I'm genuinely unable to explain my position, but my gut says go with the 320Wp's. BUT that's not a recommendation, simply a confession that in this instance I don't know what I'm talking about. Quite cathartic that!

BTW, sorry to be 'that guy' but your figures aren't "£1.26 per kWh", not even £1.26 per kWp, they are £1.26 per Wp. Fussy yes, but means we are all talking from the same baseline.

(in for a penny - technically it's £1.27/Wp ...... sorry can't help myself)

pinnks · 3 August 2018 at 7:08PM

Mart,

I totally get what you are saying as the exact same stuff was in my head - how sad is that - but I tried to put that to one side and be completely and explainably objective - and explainably isn't even a proper word!

gefnew · 3 August 2018 at 7:25PM

Hi all
But this could be future proofing for batt install, ev, v2h etc.
where is the limit.
regards

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