advice on installation of solar panels

[zipper]

Been learning a lot just reading today on here. Hoping that someone can give us advice on three quotes we've received.

Location: south facing roof of two storey semi. No shading, no obstructions.

Quote 1:

• local installer, small family business, small profit last year
• 12 x 300W JA Black Percium (3.6kW)
• Solis Mini 4G inverter
• 2 yr insured guarantee on work
• £4450

Quote 2:

• local installer, larger family business, £150,000 in the red last year
• 12 x 300W Piemar Black PERC (3.6 kW)
• Solis Mini 4G inverter
• 10 yr insured guarantee on work
• £5800

Quote 3:

• national installer, large profit last year
• 14 x 280W JA monocrystalline silicon (3.92 kW)
• Solax inverter (no details on model yet)
• 10 yr insured guarantee on work
• £5205

Thanks very much.

 

[zipper]

just had info from the Quote 3 firm to say the inverter is a Solax X1

 

[whinmoor]

Will 14 panels fit? If so, why don't the first and second quotes offer 14 panels? Then you could be up to 4.2 kW.

 

[zipper]

thanks for the reply Whinmoor. We'd certainly prefer to get as much as we can from it. Would 4.2kW be OK for G83?

Any difference between those two inverters or the different panels?

I asked the guy for Quote 1 why he offers only a 2 year guarantee on workmanship. He said any issues would show up by then in any case so no need for longer. Sound about right?

 

[Gary K]

You can get away with 4.2kw, as long as the inverter limits output to 16amp

I would go for a longer guarantee, If the cables are not clipped up (for example) they may take more than 2 years to wear through on the tiles.

Cant comment on the different panels or inverters but of the 3 quotes, I would take the last one. The first dosen't give a long enough guarantee, then second installer isn't going to be around much longer with losses like that and if they are struggling, the first thing that they will cut will be the insurance premiums.Also you are paying more for less!

I would also get a immersion controller added to the quote if they can fit it so that you use the maximum generated electricity heating your water rather than exporting it( although I noticed that the X1 has export control so may be able to do this)

 

[whinmoor]

SolaX offer both a regular and hybrid inverter which are known as X1. I presume the quote is for the basic version but it may well come with a 10 year manufacturer's warranty.

The Solis inverter usually only comes with a 5 year warranty (which can be extended for additional cost). The inverter is the most likely component to fail so a decent warranty is sensible.

The Solis can certainly take 4.2 kW of panels and I'd oversize it if space permits. But, has the third company measured your roof accurately?

Are the panels going on the front or back roof? If the back, do you need all-black panels? JA Solar is a top brand which we've used many times. I've heard of but never used Peimar so can't give feedback either way.

I'd say the second quote is the least attractive of the three.

What's the roofing material? Concrete tiles or something different?

As suggested, go for an immersion controller first if you have a hot water cylinder. If not, does your budget stretch to a battery storage system? You can then benefit from the 5% VAT rate on everything whereas retrofitting a battery is 20%.

Finally and most importantly, how did you "feel" about the companies? Did they send a proper surveyor round to look measure up and design a suitable system? Or was it a salesman who won't care about you after he's received his commission?

 

[zipper]

sorry... very busy my end so wasn't able to get back to you before now.

Roof is normal concrete tiles.

I should have mentioned that this is for a rental property and we're overseas so we've not yet met anyone. It looks from the details as if the two local firms have actually been to the property as they included photos of it that are original in their quotes. The national one hasn't so they may be overestimating what they can fit on. We'll be coordinating this from overseas via letting agency and tenant. It's a property that we're hoping to come back to next summer to live in as a retirement property. We'd like to beat the FIT March deadline to make it better value for us.

Yes it's on the back of the house and no one faces that side of the property so they don't have to be black. Are non-black panels cheaper but just as efficient then?

 

[SibertSolar]

JA panels are the better choice. Solis are popular but not as good quality, and not as well supported in the UK, as SolaX. Talk to the installer about load management (maximising self-consumption using devices such as the immersion controllers mentioned - Eddi by MyEnergi is a VERY good choice) as well as monitoring, as that will give you an idea of how clued up they are with regards getting the most out of your system. Strongly suggest you look at something like the Solar-Log SL5o if you are at all interested in monitoring the system.

Most importantly, talk to the installers and get a "feel" for them as Whinmoor suggested. Ask to see some of their previous residential installations, look for mounting system methods, cabling methods, roof entry methods etc. Ignore the product warranties, focus on the workmanship and post-install support, talk to previous clients etc, etc.

 

[zipper]

really appreciate all that SibertSolar... thanks so much for the reply

 

[bigspark17]

Just a question for you solar guys. If i turn my kettle on while in producing enough electricity myself do i pull it from the inverter or the grid or half/half?
If you have a power cut (grid side) can you still use the inverter as a back up?
Thanks

 

[Gary K]

You will use what you are producing first, with the top up coming from the grid.
If you have a power cut, the inverter will shut off completely. Its an obvious safety feature so that the poor sod who is repairing the severed cable up the road doesn't get fried with your generated power.

 

[zipper]

We've gone with the local installer who has agreed to upgrade the guarantee on his work to 10 years and to use a Solax inverter with a 10 year guarantee too. Your advice was invaluable and much appreciated. Many thanks.