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Have some PV, now looking for battery storage.

  • 19-01-2022 1:30pm
    Registered Users Posts: 1,380 ✭✭✭

    My current set-up is small compared to others being posted here but hey. I've got 5 south facing panels that produce up to 9kWh/day during summer. Planning to extend that in the future but for the time being I'm looking of getting battery storage and up to 4-5kWh should work I guess.

    I am able to do some of the work myself but will probably need an electrician further down the line. Does an installation like this need a sign off? 

    My preferences would be:

    • expandable
    • able to charge from the grid on schedule (e.g. night rate during winter) 
    • able to charge from the solar PV (take in the excess during summer) 
    • proper app/web interface
    • visible in myenergi app (does that mean AC coupled)? 


  • Moderators, Sports Moderators Posts: 18,637 Mod ✭✭✭✭slave1

    With such a small (even if expanding) system I'd look at the financials, if you do not have a Hybrid inverter you are easily looking at €3k+ for what you outline, is that Financially worth it?

  • Registered Users Posts: 2,406 ✭✭✭bullit_dodger

    I'd echo what Slave1 says, the math (probably) isn't there. If you think about it, you'll probably come to the same conclusion.

    If you have 5 south facing panels and I'll assume that since you didn't mention one, you don't have another string facing in another direction? Let's go with 360 Watts per panel, so that would be ~1.8Kwp system. So you will get that "max output" when the sun is shining directly at it in June. You obviously don't get that all day long even when the sun is shining, so realistically a good production would be 1.2-1.3Kw. Taking away a "base load" of 400-500watts for your fridge, house alarm, Wifi router, you probably just don't have enough spare juice to fill a battery on enough days. Yeah, you -could- fill one if the sun was shining all day long in the middle of June, but for the rest of the year?

    Your best bet in the short term to maximise your panels is to do things like timing your washing machine to go off at noon (if it's a sunny day)

    I'd expand your panels before adding a battery, if you could get another string up there and get to 4.0Kwp (or more) you'd be well positioned to add a battery.

  • Registered Users Posts: 1,380 ✭✭✭yannakis

    Not sure if my inverter can handle the battery or more panels. Probably needs to be replaced for either. The one I have is from Omniksol-2k-TL

    Washing machine and dishwasher consumption profiles are really "peaky" so these peaks exceed solar production even at noon. The dryer is a bit more flat and constant so that's alright.

    To be honest, I'm not sure how to evaluate the cost benefit of whole idea. One more thing I'm planning to do is also offset night rate during the winter. Charge during the 3h at night when my unit is at 5c and use that during the day.

  • Moderators, Sports Moderators Posts: 18,637 Mod ✭✭✭✭slave1

    That inverter will need to be replaced, you are looking at €1,500 alone for a 5kW Hybrid inverter that can be used to charge batteries

  • Registered Users Posts: 2,406 ✭✭✭bullit_dodger

    Yeah your right that inverter isn't a "hybrid" one, so it won't support a battery. Realistically your looking at a system replacement. Selling your existing one 2nd hand - you probably may even get a few takers here, and then using that money to put forward towards a full system replacement.

    I should also note if you look at the spec

    Microsoft Word - UserManual_OMNIK_1.5K-2K_V3.0_EN_20120706印刷版(开机选安规) (

    the max output of your current inverter is 2.3 Kwp, so you probably only realistically have the option to add 2 panels before you start getting "inverter capped".

    I did see that there are standalone battery options out there which don't plug into your solar installation and work more as "stand-alone" units, but really your best bet is to get one encompassing unit, more panels, hybrid inverter, battery. But something to look into possibly for you. I know they exist, but only passing knowledge

    As for working out cost analysis, it's a little harder as you have an existing installation and it would depend a bit on your usage. Could be done, but it's a little tricky to outline in a few lines.

    As for washing machine peak loads exceeding solar production. True most are about 2.2Kw or slightly above. So you are right that it will exceed, but even if it does exceed the solar production, your still grabbing "all" the solar that you have. Right now without a battery that solar prodcution is effectively being "wasted" by being exported to the grid. Sure, your neighbor might take advantage of the renewable energy, but you wont. So if it's a sunny day, then bang that guy on at 12:00. The heating phase is the energy intensive part usually at the start of the wash - and "solar noon" is about 12:30 in Ireland, hence starting at 12:00 and not 11:00.

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  • Registered Users Posts: 1,380 ✭✭✭yannakis

    I appreciate the feedback guys. If we get past the cost analysis, can you help me with some options for inverters and batteries? And, would it need an electrician's sign off?