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Solar Panel quote

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Essex_Jim
Essex_Jim Posts: 228 Forumite
Part of the Furniture 100 Posts Name Dropper Combo Breaker
We are looking to get solar panels installed. We drive one EV and looking to purchase a second. Presently averaging 1100 kW electricity usage per month. We are out during the day so there is only 'tick over' electricity usage during working hours.
One initial question. Speaking recently to a retired surveyor, he was negative about panels that are an 'after fit' on a roof sitting above the roof rather than in it. His concerns were bird nests, debris building up under the panels and also impacting the 'water tightness' of the roof after been fitted. Anyone have thoughts, comments on this?

On the quotes we have three so far.

Panels quoted were JA Solar and TrinaSolar (370 - 385W)

Inverter Growatt and Solis (5G and Hybrid - may be the same)

Battery Pylon and Growatt. Targeting 6.5kW

Anyone have comments / thoughts / experience on the brands / makes?

Thanks in advance of replies.
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Comments

  • QrizB
    QrizB Posts: 18,245 Forumite
    10,000 Posts Fourth Anniversary Photogenic Name Dropper
    You'll get more replies (and more info) on the "Green and Ethical" bit of this forum, there are a lot of PVers and EVers there.
    Some people have problems with pigeons but most don't. Pigeon netting is only a few hundred if it proves necessary, or you can ask the installer to include it in the quote. Roof leaks seem to be uncommon-to-rare.
    Those brands and makes are all recognisable! Pylon batteries are well thought of by their owners.
    You've not mentioned how big a PV system you're looking at. Systems have grown as panels have got cheaper and more efficient; if I was installing today I'd be able to fit 4kWh in place of my 2.7kWh, and for less than half the price I paid in 2012. Aim for a price of £1/watt for the panels and £500/kWh for the battery. Be aware the battery is unlikely to pay for itself within its lifetime unless there's a serious adjustment to grid electricity prices.
    Check out PVGIS to see your likely generation. Here in the central south each kilowatt of panel gives me around 123kWh in June but only 33kWh in December.
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Vodafone BB / iD mobile. Ripple Kirk Hill member.
    2.72kWp PV facing SSW installed Jan 2012. 11 x 247w panels, 3.6kw inverter. 34 MWh generated, long-term average 2.6 Os.
    Not exactly back from my break, but dipping in and out of the forum.
    Ofgem cap table, Ofgem cap explainer. Economy 7 cap explainer. Gas vs E7 vs peak elec heating costs, Best kettle!
  • Essex_Jim
    Essex_Jim Posts: 228 Forumite
    Part of the Furniture 100 Posts Name Dropper Combo Breaker
    Thanks @QrizB. Much appreciated. Will post over in the green and ethical.

    Thanks for the tips.
  • Petriix
    Petriix Posts: 2,296 Forumite
    Ninth Anniversary 1,000 Posts Photogenic Name Dropper
    Your problem is that you're not around to use the electricity when it's generated. The biggest saving you can make is ensuring that you charge the EVs at the cheapest possible rate. I assume you're already on Octopus Go, but if not then switch to this ASAP.

    If you want a battery big enough to charge the cars then it sounds like you'll need something massive (30kWh) but this would only save you up to £50 per month (at best  in the summer months).

    We're in all day much of the time and charge our EV from surplus solar when possible. We manage to use around 60% of what we generate but this only saves us around £20 per month on average from our 3.42kWp system. Without the FIT payments (which new systems don't enjoy) it wouldn't really be worth it.

    In your case, a simple 4kWp system for £4k might generate 4,000kWh per year. You'd probably export 70% of this, with combined earnings and savings of around £320 per year. The battery is unlikely to pay for itself, especially if are already charging the EVs at a cheap rate. 
  • Essex_Jim
    Essex_Jim Posts: 228 Forumite
    Part of the Furniture 100 Posts Name Dropper Combo Breaker
    Thanks @Petriix. Very useful information.

    As we are out all day I am looking at the battery to store what is collected and feed it back into the car(s). On the best days, would I fill a 6.5 kW battery from 8 390 W panels? Understand the comment the battery would would not pay for itself. Still would like to see the numbers.

    For sure I am looking to move to Octopus. Presently with Pure Planet with penalty until October if I leave. Trying to get a smart meter and then move.

    Thanks once again!
  • Reed_Richards
    Reed_Richards Posts: 5,307 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    edited 20 May 2021 at 8:20AM
    8x 390 W is 3.12 kW so at full output in principle you can charge a 6.5 kWh battery in under 2 hours (you wont let the battery discharge lower than 10% of full capacity).  You should achieve close to full output for a few hours on a sunny day in summer and less for a lot longer.  In practice the charging power will be limited, in my case it's a maximum of about 2.6 kW so it takes a bit over 2 hours to charge my 6.5 kW battery.  A Volkswagen e-Up is said to achieve 5.3 miles per kWh (if you believe Volkswagen) so the 90% of your 6.5 kWh battery would get you 31 miles assuming you can transfer the energy with 100% efficiency (which you can't).   
    Reed
  • [Deleted User]
    [Deleted User] Posts: 0 Newbie
    1,000 Posts Third Anniversary Name Dropper
    edited 20 May 2021 at 8:32AM
    Essex_Jim said:
    Thanks @Petriix. Very useful information.

    As we are out all day I am looking at the battery to store what is collected and feed it back into the car(s). On the best days, would I fill a 6.5 kW battery from 8 390 W panels? Understand the comment the battery would would not pay for itself. Still would like to see the numbers.

    For sure I am looking to move to Octopus. Presently with Pure Planet with penalty until October if I leave. Trying to get a smart meter and then move.

    Thanks once again!
    In the period early Autumn through until late Spring, it is unlikely that a 6.5kWp battery charged by your panels will satisfy your house needs without overnight charging from the Grid. It is also worth bearing in mind that, A, a battery will not be able to power a 7.2kW EVSE without Grid power and, B, any power from the panels to your battery to a home or EV is subject to a round trip efficiency loss. For the 13.5kWh Powerwall 2, the efficiency loss is in the order of 10%.

    A few things to consider. All homes have a baseload whether you are at home or not: solar will satisfy this first. Second, any home loads such as washing machine are also satisfied before any solar is used by battery charging. Third, depending on your wiring it may not be possible to Grid charge a battery and an EV at the same time. The EV load will be satisfied first by a mixture of battery and Grid until the battery is flat; the EV will then charge from the Grid until it is full or turned off.

    Some figures. I have a 7kWp array that generates about 6000kWhs a year. Last December, I had a forecast monthly generation output of 114.9kWhs. On my best day, my array output was 10.7kWhs: my worst day was only 262Whs. My annual Grid import is c.750kWhs. My export is about 2000KWhs/year with a total home consumption (including an EV) of 4500kWhs/year.

    If you switch to Octopus and use its Go tariff (prices recently increased), then you can only claim reduced SEG payments of 3p/kWh for any export.

    In sum, I doubt that your battery has the capacity to do what you want it to do overnight. From the time that it becomes dark, your battery will power the home and depending on how much you cook; dishwash etc there may be a few kWhs left to go into an EV.
  • Reed_Richards
    Reed_Richards Posts: 5,307 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    I have an Air Source Heat Pump.  Yesterday it drew 6.85 kWh of energy, operating in the morning and then again in the evening.  This is the output from my solar panels and the state of charge of my 6.5 kWh battery.

    Reed
  • Had my 16 panel array installed since 2011 and (touches wood) never a problem apart from pigeons.
    Soon twigged to the potential hazard when the first nest appeared accompanied by the early morning cooing. Wire mesh caging did the trick and no issues since.
    The panels generate circa 3,800 Kw per annum and a monetary income based on the 2011 Feed in Tariff contract of £2K per annum. Based on an initial outlay of £10K, and bearing in mind that the income is tax free, I don't think that's such a bad return.
    If I was installing today, obviously I would need to go a different route, and the concept of battery storage is the one which I would find appealing if the numbers worked.

  • [Deleted User]
    [Deleted User] Posts: 0 Newbie
    1,000 Posts Third Anniversary Name Dropper
    edited 20 May 2021 at 10:03AM
    If I was installing today, obviously I would need to go a different route, and the concept of battery storage is the one which I would find appealing if the numbers worked.

    The numbers do work if the array is correctly sized for the battery and home consumption. I am looking at a 20 year break even point at today's prices. That said, tariffs such as Go (less so now Agile) do distort the calculations. The FIT Scheme has rather skewed peoples' thinking about Green investments. As seniors, my wife and I have taken the view that it was the right thing to do at a similar cost to a new kitchen but with significant financial long-term benefits. Being self sufficient for energy from mid March until late September must add value to my property should we decide to sell.

    I own an EV: does it make financial sense to do so, the answer is no. People just accept that cars are a necessary expense.
  • Reed_Richards
    Reed_Richards Posts: 5,307 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    edited 24 October 2023 at 5:54PM
    [Deleted User] said:
    ...Being self sufficient for energy from mid March until late September must add value to my property should we decide to sell.
    You won't be self-sufficient in energy in the sense that you don't have to import any electricity.
    • There will be times when it is cloudy for too many days in a stretch
    • You battery won't respond fast enough to a sudden peak in demand like turning on an electric kettle and you'll have to import from the grid whilst it adjusts.  
    Reed
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