Can't decide which solar pv quote / kit to go for

wild0ne

Hi
I've had two quotes so far for solar pv. Our roof is south facing, unshaded, with 25 degree tilt angle (Installer 1) or 40 degree pitch (Installer 2).

Installer 1:
12 LG285N1C panels
Aurora power-one inverter (assuming PV1-3.6-TL)
£5,499 for 3.42 Kw system

Installer 2:
12 REC 250w Peak Energy modules
SMA 2500HF Sunny Boy
£5,800 for a 3 Kw system

For various reasons I don't have confidence in Installer 1 but I'm keen to proceed with Installer 2 (who is passionate about solar and I believe(!) is trying to give top quality product at best price). So I've asked Installer 2 for his opinion on the LG panels as on paper that system appears to generate more.

Installer 2 is not keen. He says the system usage and efficiency he has quoted for is 97%, the highest ratio of panels to inverter obtainable and that when you compare 3.42Kw panels with the Aurora inverter the ratio drops as you have to oversize the inverter to 3.6Kw or undersize it to 3Kw which would produce a much lower ratio than the SMA kit. He also says speak to his clients as they are all recording returns of 110-125% above SAP calculations. He states he can match the price of Installer 1 and would actually be on a higher margin if he did so and that he has installd the best kit (REC / SMA) on his own property.

Any thoughts please?

EricMears

wild0ne wrote: »

I've had two quotes so far for solar pv. Our roof is south facing, unshaded, with 25 degree tilt angle (Installer 1) or 40 degree pitch (Installer 2).

That seems a huge discrepancy ! Are they talking about using the same roof ?


"110 - 125% above SAP calculations" seems to suggest a basic lack of mathematical skill ! (or possibly a huge array of mirrors nearby )


10 - 25% above SAP is quite believable and could be expressed as 110-125% of SAP. The SAP 'calculation' is a bit of a joke really as it uses a location of Sheffield (regardless of where you actually live !) and even under-estimates for that. Have a look at the FAQ page (IF you can still find it now that MSE have decided to rearrange the stickies !) and consult the PVGIS webpage for a more realistic estimate (but measure your own roof angle before you bother).

wild0ne

Hi Eric

I'm guessing that someone didn't actually measure it Thanks for the info, that's really useful, will do.

tunnel

There is of course benQ and sunpower panels at 327W, 12 of these would be 3.92kWp of panels and not 3.4 as you've been quoted.

Is there any reason why you can't get 16 panels up there?,
16 x 250W panels will work out the same if not less than the LG's

Did i mention,Get some more quotes!!

If you post your general location there maybe someone on here who may be able to recommend an installer near you, can't hurt to try.

Martyn1981

wild0ne wrote: »

Hi

Installer 2 is not keen. He says the system usage and efficiency he has quoted for is 97%, the highest ratio of panels to inverter obtainable and that when you compare 3.42Kw panels with the Aurora inverter the ratio drops as you have to oversize the inverter to 3.6Kw or undersize it to 3Kw which would produce a much lower ratio than the SMA kit. He also says speak to his clients as they are all recording returns of 110-125% above SAP calculations. He states he can match the price of Installer 1 and would actually be on a higher margin if he did so and that he has installd the best kit (REC / SMA) on his own property.

Any thoughts please?

Hiya, there are loads of options regarding inverters and efficiency. I've actually got a SMA HF2500.

Some numbers, (prices are retail before VAT, and just for comparison purposes):
Make/Model Euro efficiency price
SMA 2500HF 95% £620
SMA 3000TL 96% £845
Samil 3400TL 96.5% £560
Samil 3300TL 96% £517
Samil 3000TL 96% £477

A 3kW inverter should be fine for 3.42kWp of panels, after all installer 2 is suggesting 2.5kW for 3kWp. But plenty of options between 3kW and 3.6kW.

Samil's don't have as good a shade management as the SMA's, but not a factor if you are unshaded, and they seem to be very popular with installers over the last 2 years.

As tunnel says, can you squeeze more kWp onto the roof using higher efficiency panels like the Sunpowers, Panasonic etc. They usually allow 4kWp to fit where only 3kWp of regulars will go. But the panels do cost more, perhaps 40% more per Wp for the panel element of the install.

Mart.

Fruit_and_Nut_Case

wild0ne wrote: »

Hi Eric

I'm guessing that someone didn't actually measure it Thanks for the info, that's really useful, will do.

If you decide to measure the pitch for yourself, I found it easier to do mine from inside the attic rather than standing outside in the wind and rain.

mac2008

Usually it'd be a no-brainer to go with more kWp for less cost. And there appears nothing wrong with either selections of kit.

What does 1% less theoretical efficiency actually equate to, in terms of lost FiT? I suspect it is not as much as you'd gain with an extra 420Wp of system 1. Also, efficiency will probably vary with load, with the figures quoted often the max. point on that curve. Some seem to quote 'euro-efficiency' which looks like an average, and is lower than peak.

If you've not got any faith in installer 1 and 2 can match their price, I'd say go for system 1 with installer 2, or do as Martyn wisely suggests and explore a different option like 330Wp panels.

mac2008

Fruit_and_Nut_Case wrote: »

If you decide to measure the pitch for yourself, I found it easier to do mine from inside the attic rather than standing outside in the wind and rain.

ha, yes, worth pointing this out! If you've got one of them new-fangled iPhones you can also get apps like this:

https://itunes.apple.com/gb/app/pitch-gauge/id389715382?mt=8

Mind you, apps like that are probably how you got two wildly different readings in the first place

wild0ne

Thanks so much for your replies, you've all been really helpful.

Apparently we can only get 12 panels on the roof as it's best to have a space at the edge for fixing roof if required, etc. Both installers agreed on this.

We're in Gloucester so if anyone has any recommendations do let us know!

Thanks tunnel, like the sound of sunpower and will get quote for this, suspect it might be lots more expensive to install but may well be worthwhile over the lifetime of the panels.

And thanks Martyn, really helpful info about the inverter, just what I needed!

Thanks Mac, I agree, not too worried about FiT in any case tbh, just really excited to be generating free power and supplying neighbours Wow an iphone app for measuring pitch. I was going to take a pic and use image software to measure the angle. But that would be v sad.

zeupater

wild0ne wrote: »

... I was going to take a pic and use image software to measure the angle ...

Hi

That's what I did when looking to get ours installed ... snap/upload/rotate ... angle proved to be pretty accurate.

HTH
Z