Solar panel quote - thoughts please?

Martyn1981

Bluebell1000 wrote: »

We do have room for more panels (we have quite a long SW stretch but also a SE roof, although with shading later in the day). The person quoted for a system that wouldn't need planning permission, so that there was time to fit before the December drop in FiT. Was his statement correct?

No hot water tank unfortunately, just a standard combi boiler.

Hiya, playing Devil's Advocate the installer may have said 'planning permission' for simplicity, but the reality is that PV is permitted development on rooves, even in conservation areas subject to following the rules.

I suspect what the installer means is what Zarch has mentioned, and that's the rule that systems capable of exporting more than 3.68kW need prior approval from the DNO (District Network Operator). But here's the important bit, it's not the kWp on the roof, it's the kW output of the inverter. So long as the inverter is sized at 3.68kW or capped at 3.68kW then prior permission is not needed. This is totally normal, but installers use the 4kW/4kWp claim for simplicity.

Once the panels get hot in direct sunlight they will drop about 20% in efficiency anyway, so 4.5kWp to 5kWp of panels is fine. And again as Zarch says, do it at the start, a second installer or extension won't get any FiT's, and will cost a fortune per kWp since you'll still be paying for scaffolding, labour, time and trouble etc even for just a couple of extra panels.

Edit - Also putting panels on two different orientations but linked to the same inverter means you can go bigger too, since all the panels won't be peaking at the same time. My mix (see autosig) can only hold a peak of 4.2kW, but SE + SW will have a closer peak than E + W.

Another benefit of two rooves, especially two southerly rooves like you have, is to spread generation out more evenly rather than a strong peak around 1pm (BST). SE + SW would be slightly flatter generation curve and mean more gen earlier and later than a strictly south facing system. Nice combo, better than mine.

Bluebell1000

Thanks for explaining the planning permission reference, that makes sense. That is a fairly minimal FiT change. I did ask for a quote comparing the current price with the after December price, but that wasn't included with the quote. I have actually re-done all the figures he sent, using a more realistic 2.6% per year inflation rate for electric (which matches the 2000-2015 inflation rate over 15 years that I found, very roughly), and £120 usage at current rates.

Would we need micro-inverters for each panel if we went SE/SW, to maximise generation?

Haha at Merlin139 - we never do ironing. Maybe I'll have to start ironing in the summer if we have solar panels, just to use up electric :rotfl:

tunnel

If you were to go with the SE aspect you'd probably need to consider micros or solaredge to "iron" out(sorry) any issues with the shading you say you have late in the day.
Solaredge is similar to micros where each panel will work independently to each other. Several of us have solaredge connected systems, they work a treat and come with lifetime free online monitoring(bonus) where you can see how each panel is performing. It comes at a higher price but hopefully helps when it comes to pay back!!

Martyn1981

Bluebell1000 wrote: »

Thanks for explaining the planning permission reference, that makes sense. That is a fairly minimal FiT change.

I'm in full agreement that you shouldn't rush especially as the FiT revisions are minimal, but just thought I'd mention a little 'quirk' this quarter so you are fully informed.

In April the FiT rate gets an inflationary uplift, but the first uplift is in the year after the install, so an install on 31/12/18 will get an uplift in Apr 19, but an install on 1/1/19 will have to wait till Apr 20. [Export rates go up in Apr regardless of install date.]

Again, not a major concern, and in a week or two I wouldn't have mentioned it, but in late Nov it might be worth knowing.

BUT ..... you'd be better off getting a better deal and saving a few hundred pounds on the install cost v's rushing for an extra inflationary uplift, if you can't manage both before 2019.

Bluebell1000

Different company. Same price. Same spreadsheet. 12 x 315kW panels. £517 per year saving on electric. 6 year payback time. Wouldn't listen when I suggested that was unrealistic... :rotfl:

Bluebell1000

How about 4.2Kwp system; 14 x 300W Perlight panels, Solar edge, £5600?

Martyn1981

Bluebell1000 wrote: »

How about 4.2Kwp system; 14 x 300W Perlight panels, Solar edge, £5600?

How about asking for 2 extra panels, that would be a decent package/price I think?

Edit - the 3,680W Solaredge HD inverter can handle 5.7kWp of panels.

Bluebell1000

Just to double check - we told the 2nd person we'd not be going with his system and he asked what system we'd liked from the other quote. He said without a DNO application for the 4.2kW one, if anything went wrong and it was checked, then it'd be switched off for being too large. That's rubbish, right? As the inverter would cap what's being put back into the grid anyway.

Bluebell1000

To be more exact, this is the revised quote from #2 inc. their comment:

14 Q cell 315w solar pv panels, solar edge optimisation system for £5495.

Please be minded this installation would require a G59 application your local domestic network operator prior to installation. Failure to do this could result in them switching off your system and decommissioning it as the total installed capacity is over 4.0kwp. We would do this application for you at no charge.

Martyn1981

Bluebell1000 wrote: »

Just to double check - we told the 2nd person we'd not be going with his system and he asked what system we'd liked from the other quote. He said without a DNO application for the 4.2kW one, if anything went wrong and it was checked, then it'd be switched off for being too large. That's rubbish, right? As the inverter would cap what's being put back into the grid anyway.

Yep, it's rubbish. The DNO needs to give prior permission if the system can export more than 3,680W. The rules are based on kW of export, not kWp of panels installed.

I suppose it says something that most companies inverters are rated in whole or half kW's, 2.5kW, 3kW etc etc, apart from them all having a stand out 'oddity' inverter of 3.68kW. If you look at the Solaredge HD inverter link I gave, their inverters start at 2200W, then increase 'sensibly' all the way to 6,000, apart from the strange 3,680 one.

You can ring your DNO and ask for clarification if you are unsure, or perhaps their website will clarify.