Solar panels and battery - any real world reccomendations?

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We're gathering a couple quotes for a new solar installation. Probably also doing a ASHP but purely on the solar side would be looking at ~16-20 400W panels, and 5-10kWh of battery storage (initially).

The main variables I'm dealing with are:
  • Value of an iboost for the hot water with the ASHP. My understanding is that the ASHP has a better energy conversion ratio, so it would make more sense to send excess energy back to the grid.
  • Roof is east and west facing - most of the quotes want to fill the east roof, which is fair given it gets more sun, but I'm more inclined to have it split on both sides so that my generation is spread out across the day. Would also help with feeding back to the grid during peak demand where the payback is better.
  • Is it worth getting optimisers when the only real risk of shade would be clouds and maybe the chimney (depending on panel layout)? Doesn't feel worthwhile.

Thoughts and suggestions appreciated.
 
@Mesai fill both roofs with panels, and make sure you've got a big enough inverter to cover all the output. You can never have enough panels, unless you've got a huge amount of space, winter is where the additional panels will greatly help, and in the summer you can export the excess if the DNO allows above 3.6kW export.

If the only cause of shading is clouds then no need for optimisers, you may need them if the chimney causes significant shading.
 
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Mesai said:
  • Roof is east and west facing - most of the quotes want to fill the east roof, which is fair given it gets more sun, but I'm more inclined to have it split on both sides so that my generation is spread out across the day. Would also help with feeding back to the grid during peak demand where the payback is better.
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I've put more emphasis on my morning sun generation than evening. You want to get some power into that battery as soon as possible. As soon as you're a few % above the battery baseline - you can start using shorter bursts of high power without having to resort to using the grid (eg, boiling a kettle, making toast, microwave etc).
Mesai said:
  • Is it worth getting optimisers when the only real risk of shade would be clouds and maybe the chimney (depending on panel layout)? Doesn't feel worthwhile.
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If you've not got shading, I'd avoid the expense / potential long term failure risks. Modern panels are pretty good at bypassing shaded panels anyway.
 
Ron-ski said:
@Mesai fill both roofs with panels, and make sure you've got a big enough inverter to cover all the output. You can never have enough panels, unless you've got a huge amount of space, winter is where the additional panels will greatly help, and in the summer you can export the excess if the DNO allows above 3.6kW export.

If the only cause of shading is clouds then no need for optimisers, you may need them if the chimney causes significant shading.
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Realistically we could probably get ~26 panels up there and I'm inclined to do it given the scaffolding faff. The house is relatively new so can hopefully get G99 approval, but will be trying to spec the inverter as large as possible, especially with the ASHP.
Bug One said:
I've put more emphasis on my morning sun generation than evening. You want to get some power into that battery as soon as possible. As soon as you're a few % above the battery baseline - you can start using shorter bursts of high power without having to resort to using the grid (eg, boiling a kettle, making toast, microwave etc).

If you've not got shading, I'd avoid the expense / potential long term failure risks. Modern panels are pretty good at bypassing shaded panels anyway.
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That makes sense. My understanding is that most modern panels have bypass diodes to deal with this issue - obviously an optimiser can make it more efficient but probably not enough to warrant the cost. I'm doing checks on the chimney shading to see whether it can be worked around.
 
I have been chasing some quotes for a solar install, first one has come back as follows:

  • 410w Canadian Solar Mono Panels x 12
  • 9.5kw Givenergy Battery
  • 3.68kw Inverter (Limiting so DNO isnt required)

I have been quoted £13k for this install, which included a £850 charge for the system to to used as backup in the event of a power cut and £570 for iBoost, but he didn't know I have an ASHP system so looking at posts above not sure if that's required.

I guess my query is around the inverter and if its better to go larger and just get a DNO, I am i no rush for this just want to make sure its a good system installed, any thoughts on the panels, battery and pricing?
 
Seems a bit expensive to me. For reference, I paid £4600 for 12 x 380W JA panels with a 3.68kW inverter (Oct 2021) and then £5600 for an AC coupled GivEnergy 9.5kW (last month). So all in I paid £10,200 plus £360 for SSEN to "witness" my battery install. That was including 20% VAT on both of those as the solar was done before the government introduced the 0% VAT incentive and the battery install on its own doesn't qualify for it.

As for the inverter sizing, others are probably more experienced to answer that but I was under the impression your inverter should be undersized compared to your PV output and inverters around this size are typically 3.6kW or 5kW so you'll either be under or over/matching your PV output.
 
Bigger is always better. Especially if you're wanting to hit the #1 spot in PV output, or generate a profit from exporting energy - and initial outlay isn't all that important.
 
From my reading this under sizing of inverters is a bit old fashioned going back a decade when inverters where not very efficient but it is your choice.
 
200sols said:
From my reading this under sizing of inverters is a bit old fashioned going back a decade when inverters where not very efficient but it is your choice.
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I think it's also tied to the G9x approval thing, where some installers might be too lazy to apply, or the building just doesn't have the wiring for it.

3.6 is probably enough for most day-to-day, but it hurts export and your ability to move away from gas heating. 1 microwave would use a 3rd of the throughput, which isn't great.
 
Mesai said:
Realistically we could probably get ~26 panels up there and I'm inclined to do it given the scaffolding faff. The house is relatively new so can hopefully get G99 approval, but will be trying to spec the inverter as large as possible, especially with the ASHP.

That makes sense. My understanding is that most modern panels have bypass diodes to deal with this issue - obviously an optimiser can make it more efficient but probably not enough to warrant the cost. I'm doing checks on the chimney shading to see whether it can be worked around.
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We installed 26 x 400 Hyundai shingle panels in September 2021. Each panel is subdivided into 10 sections of 40 Watts each to combat shading. At that time they were the only panels I could source which would do this. 7 panels do have major shading issues with another 5 slightly affected. With no evidence to support my belief that they were a good choice, I leave it with you.
As others will tell you the panels are the cheapest item to buy and most expensive to fit, so maxing out does pay.
 
+1 for east and west. It will give you a nice long day of power production so you rely less on batteries. We have e, s and w panels, e and w produce about 1/3 less than the s but do produce for longer in the day between them. It’s great in summer at 8pm and still covering full house load.
 
SBo said:
+1 for east and west. It will give you a nice long day of power production so you rely less on batteries. We have e, s and w panels, e and w produce about 1/3 less than the s but do produce for longer in the day between them. It’s great in summer at 8pm and still covering full house load.
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Last year we produced 888kw per installed 1kw of panels on the east roof which has the biggest shading issues with our Hyundai panels. On the south roof where the shading is still an issue the figure was 1061. For comparison our original panels with virtually no shading issues produced 1105. They are also on the south roof. We do live on the south coast and last year was a good one for solar. Figures from Germany show an East/West set up will give you about 80% of a south facing one.
 
So my sparky has been in regards my underperforming batteries.
No joy, everything seems ok on testing, voltage etc but he said he cannot test current and thats where the issue lies.
He would need to drain all the batteries and then charge them one by one (and ideally see both sides of the cycle for each battery in isolation)
Of course the BMS which is a separate module could be at fault as well.

Hes going to suggest a full swap out but doesn't think the bosses will like it.
Hes going to suggest they go back to the manufacturer again so this may get interesting.

Incidentally he said they are about to start subcontracting for Eon so will be rebranded in their workwear.

Lets see what communication I get (probably tomorrow) about their plan.
He did say he had never had this issue and they all had been fine. I wonder however how many people would really check in enough detail.
I mean it struck me immediately that they were simply not pulling enough juice when I looked at the charts, but I am sure many people wouldn't twig that 5500w being drawn from grid means you need to do that for 2 hours minimum (assuming no losses) in order to charge 11kwh.
 
Mercenary Keyboard Warrior said:
So my sparky has been in regards my underperforming batteries.
No joy, everything seems ok on testing, voltage etc but he said he cannot test current and thats where the issue lies.
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thats annoying but i guess not all that surprising & i'm defiantly in the 'not really checked or questioned it due to the complexity of trying to cancel the rest of the noise - but it does look like i'm charging faster that it should do...
 
Siliconslave said:
thats annoying but i guess not all that surprising & i'm defiantly in the 'not really checked or questioned it due to the complexity of trying to cancel the rest of the noise - but it does look like i'm charging faster that it should do...
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I would say, and take this with a semi pinch of salt, that if the last chunk of battery* to charge does so faster than the rest then you have possibly the same issue.

* If charging from very low that point is likely around 80%+ SOC, but if your topping up from say 50-70% it may be the last 5-10% that charges very quickly.
 
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