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Is it worth my while getting a battery?

  • 03-05-2023 9:39am
    Registered Users Posts: 7,737 ✭✭✭

    I've got 2 solar hot water panels on my roof, that work independantly and give me water for showers for almost 6 months of the year...

    I also have two PV panels (spec unknown), that were installed as part of the build, with a 5KW inverter. I've generated about €500 of power over the last 18 months & in the past few days my daily generation has been between .4kw and 2kw. april was 48.8kWh. It doesn't make sense for me to go on a smart meter plan, the increased charges would be more expensive than a regular contract even when recouping from the grid. I'm confident that the power I've propduced on my roof is going straight out of the building without any of that power being used by me...

    Is it worth my while adding any sort of battery? It seems like it'll cost me more than its worth... I believe Zappy are working on a smart car charger that has a bttery built in (draws from solar as a priority), I don't have an welectric car, but I'm sure I will eventually.

    Theres no more room on my roof for more panels...



  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    For my own experience, I just got a 10kWh battery installed to complement my 6kWp of panels

    Last month I generated 665kWh of which I consumed 417 (65%). This was while using the Zappi to charge my EV for free for nearly a month, giving me over 500km of free driving

    I also imported 447kWh from the grid

    In the past two days, I've imported 2kWh from the grid and my self use rate is over 90%. Multiply that out for a month and add in some extra for charging the EV you're probably looking at ~140kWh of consumption, almost all at the cheaper night rate

    What I've found is that having the battery takes the thinking out of the solar panels, you just start the appliances sometime in the afternoon when the battery has charged up

    Having the Zappi is a bonus, but I don't think I'll be getting the same levels of free driving as last month

    Now in your case, you'll need to consider how much power you can get out of the panels on a good day and how big a battery this can fill, which will kind of determine the size of battery you should get

    You may also need a new inverter if your current one isn't a hybrid inverter, which could add some consideration costs

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 1,442 ✭✭✭DC999

    For you, a battery is not worth it. You produced 50kWh in April, my 16 panels did 400kWh. And mine isn’t a large system.

    If you’ve a smart meter you can paid for the units you don’t use (called FIT) and is ~20c a unit. So you’d get 50units x 20C for April as a refund on your bill. You’ll never recover the cost of a battery. Your roof is full you said so you can’t add more solar.

    I’d suggest people look to get solar first, then a battery is a ‘nice to have’.  

  • Registered Users Posts: 1,427 ✭✭✭Big Lar

    For me the battery is a win as I charge it by night in the winter months on cheap electricity and use it by day, I reckon thou its only a matter of time until the night rate is reduced from the current 9hr window as with all the electric cars coming on stream there will be no requirement for the grid operators to sell surplus energy cheaply by night.

  • Registered Users Posts: 7 jim-osullivan

    How long does it take to charge a 5kw battery from the grid.

  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    Depends on a few factors including your inverter size and how much power it can charge the battery with, and how much power the battery can be charged and discharged with

    In general, a 5kWh battery would take 1 hour to charge from a 5kW inverter. A 2.5kW inverter (or if the battery is limited to this for whatever reason) would double the charging time

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

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  • Registered Users Posts: 7 jim-osullivan

    Thanks for reply.

    I was asking about charging from the grid as I am considering using the 2am to 4am Electric Ireland night boost.

    Also would like to know how long would it take to charge 10kw battery from the grid.

    Can these be charged within the 2 hour period.

  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    Do you know what model inverter you have? That'll probably be the determining factor

    Btw, battery capacity is kWh not kW. Kilowatts are instantaneous power whereas kilowatt hours are energy capacity.

    A 10kWh battery would need a 5kW hybrid inverter minimum to charge in two hours

    A good analogy is kW is like horsepower for an engine, and kWh is the fuel capacity of the tank

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 7 jim-osullivan

    Thanks again

    The inverter is Sofar Solar 4.6 kw total invertor rating

  • Moderators, Home & Garden Moderators Posts: 5,991 Mod ✭✭✭✭graememk

    I think your max charge rate is 3kw

    So 10kwh will take over 3 hrs,

  • Registered Users Posts: 1,009 ✭✭✭Mr Q

    Do you know if it is a EP or ES version of Sofar hybrid. The EP version would charge at 5kW

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  • Registered Users Posts: 7 jim-osullivan

    It's the ES version.

  • Registered Users Posts: 3,488 ✭✭✭Ginger83

    Do you mind sharing the battery type and cost?

  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    I got 2 of these batteries, but tbh they're pretty much all the same these days

    I'll PM details of who I bought it from and the price

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 7,737 ✭✭✭Bluefoam

    I would be very interested too. I'd be grateful if you'd share the info with me.

  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    PMs sent

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 444 ✭✭alan kelly

    I have a 5kw battery and also charge at night rate,, should I continue this during the summer ?

    I charge both cars at night and heat the water for the showers. I have a heat pump but prob won't use it much during the summer months ?

  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    You probably don't want to fully charge the battery at night, but you'll likely want to keep a charging window to ensure the cars don't drain the house battery

    I've mine set to charge from midnight to 3am to give the cats 3 hours of charging, that's more than enough for now to keep up with any diving we're doing

    I've set the inverter to charge the house battery to 40%. I could go lower but it means I've got some usable energy in the morning and it won't start importing from the grid before the sun starts shining

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost

  • Registered Users Posts: 444 ✭✭alan kelly

    I charge the 5kw battery at the low rate between 2-4am and allow it to start using the battery after 8am,, ie the first 5kw used after 8am in the house is from the low rate through the battery..

  • Registered Users Posts: 2,507 ✭✭✭bullit_dodger

    Bear in mind that day rate starts at 9am in the summer. So you are in effect using your battery with the 10% losses etc to provide "night rate" when in fact you could simply take it from the grid anyway.

    Need to start at 9am Alan. In winter it's 8am alright.

  • Moderators, Home & Garden Moderators Posts: 5,991 Mod ✭✭✭✭graememk

    From what I've seen, smart meters do observe DST and don't move like the traditional d/n meters

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  • Registered Users Posts: 2,507 ✭✭✭bullit_dodger

    Ahh good to know - didn't realize that, but I suspect Alan is on the old D/N meter like most of us as the smart meters "in D/N mode" will only be available from "Autumn 23".

  • Registered Users Posts: 444 ✭✭alan kelly

    Cheers folks, Im actually on a smart meter but on my contract is the Home Electric and Night Boost from Electric Ireland.

    Day: 08.00 - 23.00, Night: 23.00 - 08.00 and Night Boost: 02.00 - 04.00.

    Surely this stays the same in summer ?

  • Moderators, Home & Garden Moderators Posts: 5,991 Mod ✭✭✭✭graememk

    Yeah it stays the same on the smart meters as far as I know

  • Registered Users Posts: 37 oojohoo1


    It depends on your plan.

    We are with SSE and on a 24hr meter rate as that's what works best for us.

    Import rate is 32c after tax. Export rate is 24c. So if you think about it, if you export everything and buy it back at those prices, its only costing you 8c per kWh.

    We used 885kWh from our battery in the past 11 months. If we take it that it cost us 8c per kWh that's €70.80. It would take 15 years for the battery to pay for it self if it cost €1000. And your battery might last to 10 years if you are lucky.

    My advice would be to forget about the battery.

    Unless you live in an area where there is a high volume of power outages??

  • Registered Users Posts: 7 jim-osullivan

    Haven't got a battery yet but wondering how do you set it to charge say between 2am and 4am.

  • Registered Users Posts: 6,158 ✭✭✭con747

    There are settings in the inverter for set charging times, plenty of YouTube videos on it if you google it.

    Don't expect anything from life, just be grateful to be alive.

  • Registered Users Posts: 7 jim-osullivan

    Thanks for your advice con747.

    Found this helpful youtube

    videoSolis Hybrid Inverter - Self-Use with Time Charging - YouTube

  • Registered Users Posts: 185 ✭✭Baoithin66

    Hi could you also pm details of where you got the batteries. thanks

  • Registered Users Posts: 110 ✭✭Scoopsire

    Hi could you pm the details of where you got the batteries please cheers

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  • Registered Users Posts: 11,134 ✭✭✭✭the_amazing_raisin

    PMs sent

    I'm going back to my installer and asking for a referral bonus, I feel like this is the fifth time I've sent their details on

    (I'm joking of course, I'm not affiliated with them and if I was I'd tell ye before I posted 😁)

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost