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considering solar powering my home : small 3 bed semi d

  • 21-01-2020 6:18pm
    Registered Users Posts: 419 ✭✭ mkdon

    any advice appreciated .... how much would it cost ballpark and how much would it save monthly yearly?

    is any maintenance required ....

    any advice whatsoever


  • Closed Accounts Posts: 3,364 ✭✭✭ rolion

    My advice is to grab a big cup of coffee and read through all the topics here.
    You will find many answers to unknown questions...

    Happy harvesting.

  • Registered Users Posts: 64 ✭✭ Zardaz

    You need to consider the following:

    1) How much electricity do you use per year(in KWh)?
    2) Is the house occupied (i.e. using electricity) during the day?
    3) Do you have Gas central heating?
    4) Do you have an electric (heater) shower, or use preheated hot water from the cylinder?
    5) How much hot water do you use daily?
    6) How is that water heated?
    7) Do you have, or are you planning to get an electric car?
    8) Are you on night saver electricity?
    9) Do you have a south-ish facing roof?
    10) What are the dimensions of the south-facing roof?
    11) Is that roof reasonably clear of shadowing for most of the day?

    The aim is to calculate:
    A) How much solar electricity you could potentially generate during the day,
    B) How much of that you would actually be able to (economically) use during the solar day.
    (the rest gets given away free, at least for now, until a feed-in tariff is introduced)

    You can also use batteries to store a few (roughly 2 to 8) KWh of excess generated electricity each day (if any), and use it in the evening/overnight, but the payoff calculations for that is more complex, as the battery system is expensive and also has an effective cost of several cents per charge/discharge cycle. (the batteries wear out after several years)

    You could use a diverter to run your immersion with excess solar power, but since the cost of the extra kit is ~€500, the payoff is marginal unless you actually *use* a lot of the heated water. An 18 KW Gas Boiler sucking gas at ~5c/KWh is relatively fast and cheap to heat a 150L cylinder (~50 cents)

    If a feed-in tariff is available, it might be easier and more economical to sell the excess electricity (at wholesale of 5c), buy the gas to heat the water when you need it, and skip the €500 diverter altogether.

    Getting back to your question:
    System costs vary from (very approx!) 5K to 10K (after grant)
    Solar Payback time will equal (System Cost)/((Cost of energy saved per year)+(Annual feed in tariff income))

    Solar thermal will just give you plenty of free hot (or at least warm in the winter) water, but you should budget a maintenance cost of a few hundred every few years for a plumber to keep it in top order. Again, if you already have gas (or heat pump) heating available, and aren't using a lot of hot water, solar thermal might not be of economic value.

    The solar electric should be maintenance free (no moving parts or fluids), unless the inverter (which is carrying several KW of load) dies out-of-warranty. The batteries (if any), may need replacing after a few (10?) years, but by then, new storage batteries should be cheap as chips.