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Adding solar to existing Air to water system.

  • 25-07-2025 10:53AM
    #1
    Cookiepus
    Registered Users, Registered Users 2 Posts: 123 ✭✭


    Sorry if this has been asked before but I did search.
    We have a well insulated B-rated house around 5 yrs old.
    Underfloor/Air to water system works ok but electric bills are high in the winter.
    I have solar panel sales people telling me I should get panels to help with bills.
    But the obvious issue is the system wants energy on winter evenings when there is no sun.
    So I need to go get expensive batteries as well.
    I'm finding it hard to get independent advice that isn't coming from solar salesmen.

    The heat pump is (by far) the number 1 cost of the energy bills.

    If the panels cant help with these bills it would be 100 yrs before they pay back on cost.

    Thank you



Comments

  • #2
    graememk
    Moderators, Home & Garden Moderators Posts: 7,128 Mod ✭✭✭✭graememk


    Yes solar (alone) will help the bills, but not by reducing the winter bills but by reducing the summer bills (or even building up credit in the summer to help pay for the winter)

    Without a battery system, your house will use whatever it needs of the solar thats available and any excess is exported for (currently approx 20c/kWh)

    This is a very good predictor of a monthly and yearly solar generation, https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

    If you put a sample system in, it will tell you what it would generate in a year, and id estimate 40% self use and the rest exported. Will roughly work out your yearly savings.

    Batteries,
    Currently because the export rate is so good, batteries really only pay off in load shifting, eg charging on a cheap night rate and then using that during the day.
    Off the shelf are still relatively expensive but if your interested there is quite the mega thread of "DIY" batteries.

    It did start off with bare cells etc, but now, id say the advice is to get a kit, that has a box and bms, get cells and assemble everything.

    Eg websites like the likes of fogstar do complete kits, Gobel power do assembled batteries, bit more expensive or going the complete alibaba route with the yixiang battery box, (some even have EU Stock for fast delivery)

    Nkon.nl is usually good for buying cells, but the stock varies, as the shipments come in.

    (for the DIY, its about 1500-2000 for 15kWh ish)

    If you get solar, and think you may want batteries, get a hybrid inverter, then you can always add batteries later.
    (and a 48v inverter, that will take any battery, not tied to high voltage batteries, like sigen and huawei.)



  • #3
    Cookiepus
    Registered Users, Registered Users 2 Posts: 123 ✭✭Cookiepus


    Thank you very much Graememk.

    Lot of info there.

    Re. Solder reducing the summer bills-Summer bills drop maybe 70% when the heat pump is off.

    So perhaps in the Summer the solar might cover all our energy needs.

    Of course -i understand i need to consider the overall annual bills.

    Re. the batteries - i don't plan on doing this DIY. I have some quotes from Solar installers.



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