Is this spec right for us please ? (hopefully can see attachment?)

Have gone for a local authority group buy scheme on solar and now wishing I'd had time to investigate more about it. At a rough level have we gone for enough panels and battery please? It's a 3 bed detached bungalow currently on oil central heating. Roughly half panels on east no shading, other half west facing with some tree shading hence i went for optimisers. There is a small south facing roof on the garage that I wonder should I have had some panels on. Theres also a south steepish sloping corrugated roof on workshop at end of the garden but planner didn't seem interested on putting panels there. Two of us retired living there. Bound to get an EV at some point in the near future. Not at all sure about changing to heat pump in the forseeable future.

(EDIT. DC optimisers on every panel add roughly £700 to below.)

May be too late to ask for changes now but at least worth enquiring if though necessary.

Thank you

Other thing I wanted to ask about please was the planner said that above a certain energy input the energy would be lost to heat as the grid capped it at a certain level. Seems crazy. Sorry for my limited understanding of terminology and figures.

G98 replaced G83 on 2019-04-27. (And G99 replaced G59 for larger generators.)

Rgds

Damon

You can export for a lot more than 5p/unit at the moment. Today Octopus were paying 19p/unit for daytime solar exports, or 30p/unit if you store it in a battery and export at 5pm when the grid really needs it. Tomorrow evening they are offering over £1/unit which is much better than self consumption. (!) Is this price a blip, or the new normal, who knows?!

The financial numbers are a bit misleading IMO - they are forecasting it takes well over 10 years to recoup the cost of the installation, so the return on investment for that period is going to be nil (or less). Over 20 years they forecast a £8386 return* on £9478 investment, which is 3% pa if you still own the kit and it keeps working for that long, but that will depend what happens to energy prices and usage, and on the cost of tying up the capital to buy the kit. Can't see where the quoted 14% return could possibly come from.

*Edit: the projected income is £552pa, which would actually take 17years to break even and add up to £11k income over 20 years. Less the £9.5k install cost, leaves £1.5k profit over 20 years, or 0.8%pa, miles less than the projection. Some alarm bells there... If the financial aspect is important then do your own sums and take financial advice from someone qualified!

Not sure how it works if you have both a PV inverter and a battery system (which also includes an inverter) - G98 would consider the sum capacity of both inverters (s2.5).

If there's a safety system to monitor the overall combination of PV generation, battery dis/charging and home consumption and limit the net result to <3.8kW, it would have to be a quite smart system and type-tested. So it didn't end up charging the battery at times when it would be advantageous to export more; or cutting back the PV because the battery is taking up all the export capacity (for example). Might be better just to apply G99 for the PV+battery capacity, then the PV and battery can each do their own thing?

I have no experience so sorry if this is dumb! Damon do you know?

I have a 6kW system SSW with a 10kW battery. Based on my experiences I would say that you could do with a bigger battery. This time of year in full sun at around mid day it throws out about 3.2kW (had 6.5 height of summer)so charges the battery in no time at all. Given you are differently orientated to my set up guess you will have a more levelled output over more hours. I would check out the spec of the inverter and battery combo particularly the inverter in terms as to what power it can supply on its own and how much the battery can supply. My set up the inverter can supply 32 amps and battery 20 amps. If I have capacity in the battery I can run an electric shower or oven and top up with solar if producing, or from the grid. The system looks to solar first then battery then grid and combination of them ensuring minimum from grid. Don't understand the bit about heat if grid limitation kicks in on my system the inverter controls the solar input throttles it back then when you draw power in the house ups the solar to match.

Posted By: Nick Parsonsand I take it it's in part to optimise your 'shoulders-of-the-year' generation

I'm intrigued Nick, what does 'shoulders-of-the-year' mean please?. I feel it should mean something to do with the guilt I feel for the environmental mess oldies like me have left for the young. My main reason for getting solar was to try and do something right, so its frustrates me that energy is capped going back to the grid but I do understand it would fry in the summer if uncapped !!

Posted By: zak99 so its frustrates me that energy is capped going back to the grid but I do understand it would fry in the summer if uncapped !!

Personally I wouldnt be to worried about your export being capped as its not likely to happen often with the east west split youve got. Panels only generate at max capacity with full sun beaming square(ish) onto them which isnt going to happen with your split. Assuming 3.7kwp facing east the sun will be sideways onto them at its peak and then move round to the partly shaded 3kwp array. Both the arrays will generate without direct sunlight but your not likely to get anywhere near the 6.6kwp of the panels youve got. I think theres software available to model split systems like yours and might be worth asking your installer if they can model it for you??

If you want to do the best for the environment rather than ROI, it might be worth putting in a G99 application, binning the batteries and use a slow cooker for evening meals

Ah thanks djh. Only just come back to this. That's exactly what I meant. Accepting that however many sunny days you get winter yield will be proportionally low, but exactly what you've said relating to spring and autumn.

Zak, I think you are doing something right - it's just getting the balance I am not sure about.

For similar reasons (it feels right) I'm putting around 2200W split E/W on a small extension this year. I don't expect pay-back. I just want to do something a bit right (along with the extensive EWI we're planning).

Thanks again for the very helpful answers.

The optimisers are tigo not Solar edge, there are many similarities I believe (in my limited understanding).
I doubted and questioned the need for optimisers in the non shaded string and have asked that question again before committing to install but i may be pushing the go/no go timescale limits now.
I've also asked about apps etc for monitoring as they may perhaps be dependent on optional sender modules (?).
Also asked about possibility of moving a couple of panels to the small south facing roof, looking at the quote I'm not clear if the 10/8 split of the 18 panels is East/West or West/East. The West side has large trees in our garden roughly SSW aspect on the westside, in summer in full leaf and dense of course but the sun is higher. I raised my concern about this repeatedly. The sun clears the trees later in the day depending on time of year. Perhaps this is why they didn't move some of the panels to the small south roof (on the west side). I was assured they felt the gain will still be worthwhile but I elected for optimisers because of it.

A curious question is how do panels, batteries etc work out as far as carbon neutral, at what point roughly does an installation if ever offset carbon from manufacturing. I guess the batteries are not so good? I've been nagging a little my local council in Maldon district why new builds are not with solar and high levels of insulation so would be good to know re neutral timescale in that nagging !!

Posted By: philedgeIm not sure how the Tigo optimisers work but the Solaredge units report individual panel performance so you can see at a glance if theres a problem with a panel/optimiser. Without individual panel reporting any faults can take hours to identify whilst potentially every panel is removed for testing. Quite possible that you could blow a significant chunk of the addtional cost of optimisers fault finding on a system without individual reporting.

I was impressed by our Enphase microinverter system at the beginning of last year. Out of the blue it/they sent me an email saying two panels had faults; luckily a quick visual check showed the nature of the fault - a whole load of snow on those two panels. But still demonstrated that the system works.

Install happened last week, happy so far.

Posted By: zak99 JA Solar 370-watt panels, fitted with Tigo optimisers with a PylonTech US2000 battery system. The inverter is a Solis Hybrid 6kW Inverter.

The Solis inverter iPhone app is very poorly rated at the download page but it seems OK to me so far. Although I enquired, no monitoring of the Tigo optimisers was provided, the install planner has unexpectedly left the company now. (this was done under a LA Solar Together scheme). From reading it looks like monitoring the optimisers should be possible with the addition of something called a TAP and a CCA (Tigo Acces Point with Cloud Connect Advanced) for parts around £300. I'll see where I stand with install costs next week

Based on Phils comment below I think it will be worthwhile

Posted By: philedgeWithout individual panel reporting any faults can take hours to identify whilst potentially every panel is removed for testing

For loft-installed inverters, the summer temperature is a concern. Some inverters start to derate the output from 45 C upwards, so better keep an eye on the temperature in the loft. And perhaps look up the derating data on this particular inverter.

Posted By: jamesingramjust look into how they interact with your battery system before purchasing.

In my experience getting info on how an inverter and battery interact is like getting blood out of a stone. There seems to be a lot of secrecy presumably designed to protect the detail of the algorithms involved w.r.t the BMS.
I was thinking of a diverter for my immersion but don't think will be worth my while as have solar thermal and suspect the Inverter /BMS may not allow it anyway but I would like to know at some point.