Advice on solar panel please

Hi all, just had a quote for solar panel and wanted to check with the members here for their views please as I feel out of my depth here. 

Details of quote: 
Nominal 7.4kWp (18 panel) solar PV sytem, using premium, high efficiency panels (TRINA VERTES DE09R.05-410)
Vertex 410W all-black panels with a high quality Solis 6kW inverter (PV INVERTER - SOLIS GR1P-S6-6K)
BOS - SWITCHING, CABLE, METER, MONITORING (£467 quoted for this - no idea if meter is 1st or 2nd gen or if that is something totally different)
Total cost including installation and scaffolding is £7000

I have been told Solaredge optimiser is better than Solis, but it will add circa £1,000 to the quote. 

In terms of battery storage, adding an AC coupled Givenergy storage system with 3kW inverter and 5.2kWh would cost almost £3k and with 9.5kWh battery around £4.5k. I have been told this can be added in future, but if affordable now, it's best to do at same time as install of solar panels as that will mean no VAT applies to the battery.

The solar pv system quoted is estimated to generate around 6000kWh a year, which averages 16kWh a day, but obviously that will be lower in winter and higher in summer, perhaps over 40kWh on a good day (quote shows a monthly estimate chart). So a 5.2kWh battery is quite small for the solar but would act as a buffer for intermittent generation and demand during the day, and provide stored energy for the evening. Depending on consumption, that may be all the capacity needed, but it can be added to later on.

I am inclined to go ahead as advised by the contractor, as I trust him, but i'm conscious I havent followed the golden rule to obtain other quotes.  To me it feels like there is so much tech jargon and with so many options out there and variability in quality, I just wanted to put this out there to see if I am missing something or should be asking for something different (perhaps a bettter quality brand). 

Would welcome any thoughts / advice regarding the above. 


  • cm4ever
    cm4ever Posts: 215 Forumite
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    edited 18 March 2023 at 9:07AM
    Hi, just a couple of comments on your potential system: -

    1. There's nothing wrong with the Trina panels, although some may say go with major brands as apposed to 'Chinese' makes - it's personal choice at the end of the day and know many installations using Trina that haven't had any issues. As you'll see I have them myself, but there'll always be critics no matter what you plan to install 

    2. Originally I wanted to get Givenergy inverter/battery kit but was put off by what seems to be a lot of issues - just look at the threads on this forum - but that's not to say other makes are fault/issue free etc.

    3. Definitely get some more quotes as they could be an eye opener and may well use/suggest different kit - so worth the time spent getting them.

    4. If possible, always maximize solar panel installation size as you're only likely to do it once due to additional costs/expense like scaffolding etc.

    5. Think about what you want to achieve from your solar& battery storage system - once you know that you'll be in a better position to narrow done what you need.

    6. Although some may say the cost of battery storage doesn't necessarily give a good ROI, that's also a personal choice and how you look at it on the whole - to me solar& battery storage was like buying a car - I bought what I bought for it's intended purpose and use - the opportunity to gain bill reductions and doing a little bit to save energy consumption was enough to justify the 'initial' cost. But unlike a car, there's much more chance of it being a money saving purchase, once you accept the purchase price is just that. If you think it's too expensive for your wallet/needs or are heart set on a high ROI, battery storage may not be for you - another personal decision.

    7. Buying battery storage at the same time as the panels means no vat on the storage - enough said.

    8. Whoever you choose as the supplier/installer - they'll all to a more/lesser degree going to over promise and in some way under deliver - it just seems to be the way in this industry...

    9. Generally solar optimisers are only needed if you have the likelihood of panel shading.

    10. Unfortunately, what with inflation, energy prices and current high solar& battery storage installation demand - prices are high, but only you can decide when you want to buy/have it installed for - like anything else there's always going to people that bought it cheaper but that's no reason not to look around at different quotes/prices/system specs in the first place.

    I could go on with another couple of points about size of battery storage etc, but hopefully you get the point - don't let anyone rush you into making a decision and once you decide on the kit/spec/size etc and have it installed, just accept going forwards you did the best you could in your mind and with reference to your situation - whatever you install now will always be bettered in the future - that's just the way it is  ;)
  • Screwdriva
    Screwdriva Posts: 1,162 Forumite
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    edited 18 March 2023 at 4:52PM
    Min1234 said:
    Would welcome any thoughts / advice regarding the above. 

    Quality: I suppose I'm one who would always advise going for quality panel brands like Hyundai/ Sharp/ REC/ Panasonic/ Solarwatt panels or SolarEdge or GivEnergy for the inverter. No brand is perfect but these are known to offer aftersales/ warranty support when issues do arise, unlike some of the budget brands on offer. I'd recommend doing whatever you can to avoid the agony of dealing with brands who do not offer customer support when something goes wrong. 

    Battery: I would also advise against a battery unless you have a heat pump or electric vehicle, which typically take annual usage well above 3500 kWh per year. This calculator does a great job illustrating the difference it can make to your return on investment. If you don't care about that, then getting a battery upfront will save you the VAT. 

    Price: The price you have been offered is good. If you decide to skip the battery, I'd suggest going with SolarEdge inverter/ optimizers. If you decide to get the battery, I'd insist on the GivEnergy inverter and battery combo. 

    Best of luck!
    -  10 x 400w LG + 6 x 550W SHARP BiFacial Panels + SE 3680 HD Wave Inverter + SE Optimizers. SE London.
    -  Triple aspect. (22% ENE/ 33% SSE/ 45% WSW)
    -  Viessmann 200-W on Advanced Weather Comp. (the most efficient gas boiler sold)

    Feel free to DM me if I can help with any energy saving!
  • Hexane
    Hexane Posts: 520 Forumite
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    edited 18 March 2023 at 9:22AM
    I use a 6kW Solis inverter, likely similar or identical to the one you're being offered, with panels providing peak output almost exactly the same as what your installer is proposing. I wouldn't necessarily call my Solis inverter high quality, but it's been 100% reliable thus far, generates what it's supposed to, and that's all that really matters.

    I'm not really sure why "meter" is included, I thought all new installations now use your own smart meter for measuring the electricity you sell back to the grid. (And the panel/inverter supplier would not be involved in installing your smart meter.)

    I've always held the view that the (significant) additional cost of SolarEdge is only worthwhile if there's some shading.

    You could look around for further quotes but my guess is that in the current market, you won't beat what you've already been offered. Or else you'll be given quotes for 4kW-peak systems, which is a false economy.

    Getting the panels+inverter without the battery would work. Because of the VAT saving, actually the battery option might be value for money in this instance too.

    Worth checking if the installer plans to apply to the DNO on your behalf, for approval of the >4kW potential generation.

    And, ask about pigeon-proofing.

    Your contractor sounds trustworthy to me, too :) Monitoring being included is a good sign (this is likely a USB stick for the Solis inverter, unless it's built-in these days).
    7.25 kWp PV system (4.1kW WSW & 3.15kW ENE), Solis inverter, myenergi eddi & harvi for energy diversion to immersion heater. myenergi hub for Virtual Power Plant demand-side response trial.
  • UncleK
    UncleK Posts: 207 Forumite
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    I would suggest looking hard at batteries. I bought batteries later (but quickly) after I found that two-thirds of my power (in September) was going back to the grid. I have a heat pump plus I charge up the batteries with low price electricity at night in the winter and they save me a lot. As people say, that doesn't apply to everybody - hence my suggestion to have a hard look at what electricity you use when the sun isn't (or might not be) shining. Hope that helps and doesn't make it worse!
  • ABrass
    ABrass Posts: 1,002 Forumite
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    edited 18 March 2023 at 10:36AM
    That's unusually good value for the current market.

    Is there a reason they don't recommend a hybrid inverter instead of a separate unit?

    6,000 kWh from a 7.4kW array is fairly conservative. Is this an E/W split or do you have shading?
    8kW (4kW WNW, 4kW SSE) 6kW inverter. 6.5kWh battery.
  • yp70479
    yp70479 Posts: 54 Forumite
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    Just bear in mind that the 5.2KW Give Energy battery is 80% depth of discharge. In practice that means it has an actual usable capacity of 4.16KW. It will mop up a bit of your excess power over the summer, but given the size of array you are getting, you will still be exporting most of your excess. If you decide a battery is right for you always check the depth of discharge and usable capacity on the battery spec, that way you know exactly how much the battery will store (for example the GivEnergy 9.5 is 100% DOD so you get what you expect).

    If you have an electric vehicle you can use that to mop up a lot of the summer excess.

    If you don't then I would try to get on a tariff with good export rates - Octopus has introduced a new Flux tariff, or they have two outgoing Agile tariffs - but you have to get your import from them. Most important is to make sure you get an MCS certificate from your installer, and a copy of the letter/email from your DNO (your installer should be able to provide this) as you need both to apply for an export (SEG) tariff. You don't need to get your SEG tariff from the same supplier you get your electricity from (but some offer better deals for existing customers and a couple won't take you if you have a battery).

    I agree with the pigeon proofing and that you don't need optimisers unless you have shading. I think the "metering" may be the EM115 meter which is a regulatory requirement although it doesn't really do much!

    Just for info - I got 3.2kw of 400W Trinia panels,  Solis inverter, AC3.0 and a 8.2KW Giv Energy battery last summer - very happy with my system and no issues so far!

  • ecraig
    ecraig Posts: 227 Forumite
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    Shading isn't immediately obvious though. It can be longer distance shading. And if your neighbours have small trees today, they might be large in a few years time.

    I have an optimised array and I have odd shading from the apex of a neighbouring property at the front of my property. 
    If I didn't have optimisers all my front panels would all degrade to the lowest intake. Today I would have seen a 16 percent reduction to my front intake if I didn't have optimisers.

    I'd recommend getting a quote from a fitter who will use the solaredge software to quote and give you insights on your expected production if you incorporate an optimised array.
  • Thank you all for taking the time to provide your thoughts. This was my first post ever and I’m so glad I reached out. The comments have helped me consolidate some decisions as well as make a list of further queries for the installer. You are all amazing - thank you so much!!! 
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