Solar phase II

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  • edited 22 September 2017 at 2:53PM
    warrenbwarrenb Forumite
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    Seventh Anniversary 100 Posts Combo Breaker
    edited 22 September 2017 at 2:53PM
    I am doing exactly this, I can get 1.5kw on the garage roof and will be buying the battery at the same time to get it at 5%. Think about it, you get a 1.5kw system for around 2k, the battery is around 4k, with 5%, with 20% it is nearer 5k, so almost getting the 1.5 system for half price. Saying that I won't be going for a 14kw system as I have never used 14kw in a day so don't see the reason to have such a large battery.
    Living in supposedly sunny Kent
    14*285 JA Solar Percium Panels
    Solis 4kw inverter
    ESE facing with a 40 degree slope
  • CardewCardew Forumite
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    Alan_Brown wrote: »
    We currently have a 4kw East/West installation (2kw each side) and we've just ordered a further 1.8kw (6 x 300w panels) for a shallow incline roof on a workshop building in the garden.

    The main inverter is 3.8kw and the new inverter will be 1.5kw, so a combined 5.3 Kw system. As we're over the limit for our single phase supply we had to apply for a G83 application with the local DNO. That came back with approval and zero cost, which was great.

    The new addition won't qualify for FITS or export payments, which seems a little unfair (especially the export) but as we currently use all of our generation I am not too worried. The cost including installation is £2500, which I thought was a great price. I can't wait for it to be fitted :)

    What annual generation do you expect from the 1.8kWp new installation - around 1,500kWh??

    Do you feel the potential savings justify a £2,500 investment?
  • Martyn1981Martyn1981 Forumite
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    warrenb wrote: »
    Saying that I won't be going for a 14kw system as I have never used 14kw in a day so don't see the reason to have such a large battery.

    Hiya. That's how I've done most of my battery pondering, suggesting 4kWh useable (around 5kWh Li-ion) would do the job.

    But, I'm having second thoughts now, for a number of reasons, though none are entirely compelling:

    1. The bigger the batt, the more you can avoid full charging, and discharging, which will extend the life of the battery.

    2. Bigger batt, allows for longer viability as it loses capacity, so if 20%+ overcapacity at the start, then if down 20% after 10yrs, it's still going to meet needs.

    3. When I'll need it the most, shoulder months, with plenty of export, but still high import, Feb, Mch, Apr & Sept, Oct coincide with when I'll be using the small ASHP. A battery would allow for more ASHP use without import. EG 2kWh per day, could mean 4hrs of heating, outside of generation, and 6-10kWh of heat.

    4. The larger batt would allow cross day storage in the 6 best months, allowing for 100% PV supply on days which are extremely poor. Not really a concern normally, as these days are so rare, and going larger just isn't economical on this basis alone, but as part of this list, perhaps.

    5. Future EV use. On average in the summer I have 20kWh of generation, reducing import from 7.5kWh to 2.5kWh per day. After allowing for domestic use of the battery I'd still have 10kWh+ of spare charge, or around 30-40miles of motoring per day (which we don't do). So a larger batt may help to future proof for a PV, though the savings here would be smaller as presumably the alternative would be a cheaper night rate for charging.

    6. Bigger batt, especially the PWII is cheaper per kWh.

    As I say, none of these arguments are convincing, and I'm not sure all of them together are, but worth a ponder I think, if the decision on battery size wasn't clear cut.

    [I'll cross post this on the domestic battery thread as it might be useful, or not! M.]
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • Cardew wrote: »
    What annual generation do you expect from the 1.8kWp new installation - around 1,500kWh??

    Do you feel the potential savings justify a £2,500 investment?

    I'm not overly concerned about the 'investment' side of the installation. However, to answer your question, I did an online check and the average cost of clean electricity at the moment is 15.37p per kw/h.

    Taking your figure of 1500kwh pa x .1537 = £230.55 per year

    £2500 / 230.55 = 10.84 years until the array pays for itself.

    The improvement to our home's carbon footprint doesn't have a monetary value, but does have great value to our family. The reduced exposure to fluctuating energy prices is also something that we will value as a family.

    My wife an I are looking to become more self-reliant and self-sufficient. Energy security is right up there on the list.
  • The panels are being installed today, we're chuffed to bits to see our plans moving along :)

    I should update my signature like many on here (and Navitron do).

    2kw West, 3.8kw East.
    Half an acre allotment (WIP)
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