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Solar PV battery options



  • Registered Users Posts: 3,015 ✭✭✭ irishchris

    Sound, that's a shame as emailed them direct fee weeks back and they told me would be here by q4. Might email Quentin so tomorrow and see if any way of reserving one for when they get stock next year

  • Registered Users Posts: 3,015 ✭✭✭ irishchris

    That's very true now in August but come November December and January I think we will need every bit of our 20kw batteries. Granted some days will be 4/5kwh generated but there will be many 1kw days too

  • Registered Users Posts: 1,799 ✭✭✭ SD_DRACULA

    Had a look at last year's data and from Nov to Feb, nothing over 10kwh per day so it will be tricky to get it right.

  • Registered Users Posts: 5,541 ✭✭✭ championc

    For me, with 20kW, for wintertime, I'll be able to charge to maybe 60% each night. If we have a cracker of a day, I'll have the space for it, and on a crap day, I'll have enough to get me to 23:00 for when the night rate kicks in.

  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    Fair price for 10kw puredrive battery?

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  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    how much load shifting can I forecast with a 5 or 10kw battery per annum?

  • Registered Users Posts: 3,927 ✭✭✭ graememk

    Do you mean charge at night and discharge during the day?

    I suppose Oct - march, for 5kwh.

    For calculating savings, let's take 10 kwh for example, and use energias ev tariff as that's the hot business now.

    10kwh of night, will be 85c

    I'm measuring a round trip loss of 20%. (Ac in, ac out) so you'll get 8kwh out.

    28.82c day which is 2.30, 1.45/day

    (It will be more like 8-9 in and 7ish out, as your discharging to 10-20%) so likely more like 1.20 per day

    Nov-feb for sure, that's 120ish days, let's add in 2 weeks in oct and March.

    160 days, 192 euro saving.

  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    Thanks graememk that is essentially where i arrived at also. What sort of self consumption are people who do not have battery?

  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    I am struggling to make the numbers work for batteries. Please correct my assumptions

    7.5KW system will produce approx 6.6KW/annum.

    10KW battery so forecast self consumption at 80%, ie. 5320KW.

    The remaining 1330 goes to the grid giving me 18c FIT or 240 euro/annum.

    Of the 5320 consumed, I suggest 20% of that goes towards battery and avoiding night rate, so about 1050KW at 9cent, and the rest avoiding day rate of 29cents, saves me 1300 per annum.

    160 nights a year I load shift from night to day using battery. 10KW battery so in effect shift 8kw due to max discharge and loss AC/DC. 256 euro (generous).

    Load shift+direct cost avoided+FIT=annual savings

    256e+1300e+240e= 1796 (1800e)

    System cost using 1.2Kw rule of thumb is 14,000. About 7.8 years to break even.

    Assuming 45% self consuming without battery, FIT generates 658. (I can reduce self consumption without battery to 20% and big picture doesnt change much unless FIT rate collapses -which it might but not for 6-7 years).

    Consumed all at day rate (2992KW at 29cents) saves 867.

    Total savings no battery = 1525e.

    Cost of system no batteries = 9k, so 5.9 years break even.

    So, 2 extra years to break even with batteries, but save 300/annum for a period thereafter, before batteries need to be replaced. This seems a marginal gain for a lot of extra capital expense, and battery life will be degrading meaningfully after break even point, so we cant really hang our hat on the longevity of the additional savings generated?

  • Registered Users Posts: 1,662 ✭✭✭ funnyname

    I am of the same mind as yourself when you look at cold hard sums wrt to not getting a battery. Can you also save on the inverter if you don't need a hybrid one if you don't go for a battery?

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  • Registered Users Posts: 3,927 ✭✭✭ graememk

    Also, batteries just don't die, they just don't work as well, so still will have some residual value too

  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    My thinking is to get the hybrid inverter regardless. That way if batteries settle down in price in due course I can buy, or DIY, and capitalise on any technology advancement. I am curious to have my numbers challenged though. Perhaps there is a usage behaviour, a hack, or calculation I have not considered.

  • Registered Users Posts: 2,652 ✭✭✭ yankinlk

    Ok I will challenge them. Some really big assumptions on there around self consumption %.

    That will vary for each household, and has many factors... habits of using power from sun to do washing, having 2+ people working from home, ev or not....etc

    A battery has to be used daily. The bigger the battery the larger the cost and the less likely it is fully used. A smaller battery has a greater chance of being used multiple times a day... ie my 5kwh battery regularly discharges 7+kwh in a day in summer.

    I think your numbers might make sense for you tho... and I agree that unless u get a cheap battery, diy or are lucky to have a grant discount they might struggle to be anything better than a wash. Razer thin margins at the moment.

  • Registered Users Posts: 6,548 ✭✭✭ Alkers

    You need to factor in that you're only.sllowed 200e pa tax free from fit and must treat anything above that as income. This might make your non battery payback period a bit worse.

  • Registered Users Posts: 1,799 ✭✭✭ SD_DRACULA

    Those calculations don't mean anything to be honest, because:

    1. You won't have the current energia EV rate (or any current rate) for 7 years
    2. You don't know if your usage patterns will be the same for 7 years
    3. Your battery will continue to work past 10 years even, but will have less capacity
    4. kwh/standing charges will only go up
    5. Not sure about your calculation that only 20% of generation will go to battery, in August I had 42% of gen pushed to batteries (but they are 20kwh)
    6. No calculation/payback will beat that feeling of not importing much for 7-8 months a year

    The reality is that the repayment will be quicker than those calculations and at the same time let's be honest here, the only people that can afford solar right now are people who didn't have a problem with electricity bills in the first place.

    I'd say if you have people at home during the day and can easily afford the batteries go for it - you might be thinking about adding batteries next year and the cost might be double, no one knows.

  • Registered Users Posts: 2,123 ✭✭✭ bullit_dodger

    Yeah, like SD mentions above, it's a hard one to call.

    The battery math isn't as compelling as it was 12 months ago. However, the rates you use when doing the calculations flavors the outcome a lot depending on what you are getting in FIT and day/night rates etc. Forgetting the solar/FIT aspect for a while and looking at my own "grid to battery" figures for the year, this is basically the number of units I "load shifted" from night -> day rate. I have a ~9kwhr battery

    Like most things in solar, it generally follows a sine wave during the year. Assuming sept, Oct, Nov, Dec map to Apr, March, Feb, Jan (which is a reasonable guess). So, I'll probably import from grid -> battery approx. 1920 units for the year.

    Using Energia's current €0.08 night and €0.29 day....and applying losses of 10% (my GivEnery battery historically does 9%) that puts it as.

    Cost to charge battery = €0.08 x 1920 = €153.52

    Value of electricity at day rate = €0.29 * (1920 * 0.90) = €501

    Ergo savings from the battery ~ €350/year by using it to store night rate leccie and use it at day rate. This is ignoring the storing of solar generated energy which you can get FIT for also. I import from the grid in summer as I have an algorithm which looks at and decides if tomorrow will be bad weather wise and sets the charging levels.

    One massive thing that I think the battery does for you though (esp. if you're a heavy user), is that it softens the blow of the bills in winter when solar is pants and the bills are high. The battery saves ~€50/month in the dark months. So yeah, while FIT will give you money in Jun/July that you would get by not having a battery, that money is long spent out of my wallet when Jan comes about. Battery means that those Christmas bills are about €100 lower at that time of year. That's useful to me - but appreciate others may not value it as much

    Overall, it's a question of what you value more. I think you will get a quicker payback without a battery, but overall I think you have (slightly) more flexibility and will generate more over the long run with one....

    Aside: I should say, your consumption profile too is super important. I'm sort of unique as with the mining and the fact that my automation turns on/off miners when I have spare solar, I can use all the space in the batteries or create space as needed if I know it's sunny.

  • Registered Users Posts: 1,662 ✭✭✭ funnyname

    With the standing charge increasing all the time what size battery would be needed in proportion to the number of units you use in a year (with greater weight towards winter given higher use and lower solar generation) to go off grid? Add in having an EV with V2H functionality as an additional backup, is it possible for some households to do this?

  • Registered Users Posts: 953 ✭✭✭ DC999

    I'm was in the same boat and torn on adding a battery. But I'm gonna get one. Biggest non-cost reason (and I'm cost focussed generally) is solar is supposed to help our house, IE convenience to use what we want when we want it. But without a battery I will obsesssssss about self-consumption % and drive my family bonkers. No one in our house (bar me) is gonna only turn on 1 heavy electrical device at a time - meaning we're importing. And can I expect them to?? I'd like them too - but do we want to double the time needed to cook dinner :)

    Just looking at making grub, all our kitchens are energy hunger. And only the dishwasher can easily load shift.

    Another bigger for me is I feel energy prices are gonna be nuts for years (just IMO). So battery and night rate helps dampen that.

    @bullit_dodger did suggest even a small battery to me months ago when getting our quotes and that I wouldn't be ar3ed running around the house turning stuff on and off. I dismissed that. But have come around since :) Just need to find one that won't break the bank now!!

  • Registered Users Posts: 8,695 ✭✭✭ the_amazing_raisin

    For anyone who bought CALB cells from PWOD, what kind of fees are ye seeing for customs & shipping?

  • Registered Users Posts: 3,927 ✭✭✭ graememk

    It's been included in the price (so none extra)

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  • Registered Users Posts: 8,695 ✭✭✭ the_amazing_raisin

  • Registered Users Posts: 2,123 ✭✭✭ bullit_dodger

    There genuinely isn't a right/wrong answer for the battery question. I think most houses could do with one, even a small one but you wouldn't be wrong just to go with the FIT either. Even using today as an example, being early Sept we're well clear of "winter", but my automation decided to charge it up to 95% last night.....based on the forecast of today. Probably could have gotten away with charging to 80-85% if I was to be picky, but that's weather forecasting for you. Not a perfect science.

    Rain expected in Dublin from 3-4pm, so I'll be using my cheap rate leccie (€0.08/unit) once that rolls in.

  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    "But without a battery I will obsesssssss about self-consumption % and drive my family bonkers."

    HAHA. Snap.

    Appreciate the point that we don't know where prices will be in 7 years. We can only make assumptions when trying to forecast as best we can. Of course its not just a financial decision, flexibility and gadgets are cool. My bet is FIT will be less, having served its grant like purpose for 4-5 years of the transition phase.

    Throwing capital at panels now makes sense, when installers are on the roof, and FIT softens any oversizing. On FIT and income tax, i expect this to be challenged given the capital expenditure required to generate FIT. I will certainly be taking it up with my tax accountant. Throwing capital at batteries seems marginal, unlike the roof component they can be added later when prices go down, or rates go up, and the equation makes more sense, in the mean time the capital saved can be growing in a fund with material gains (so we can buy even more batteries when timing makes clear sense 😀).

    Ultimately I agree it is not a terrible decision to go with batteries, just marginal. The horrendous payback, over 12 years say, only seem to come into play when a consumer is had by a rogue installer quote....stick near the rule of thumb and the decision will be ok either way.

    The chart above showing shift of grid to battery is very helpful and interesting.

  • Registered Users Posts: 5,541 ✭✭✭ championc

    So totally with you @SD_DRACULA .

    Mind you, I've one eye too on the prospect of losing the Data / Night meter in the years ahead, while also the potential of a peak 2 or 3 hours evening teatime slot.

    20kWh of batteries gives complete flexibility, and with the Vat off at checkout, for me it was absolutely worth doing

  • Registered Users Posts: 185 ✭✭ connesha

    Agreed @championc and @SD_DRACULA

    Smart meters are coming. Many of us are on them already.

    Any chance the govt. got for the past 6 months, they've been prepping us for higher peak/evening/day rates. The difference between day/peak rates and the incoming FIT rate will likely only widen.

    No matter how big your solar array is, it's not going to cover cooking dinner at 6pm, for a lot to the year.

    The battery provides the flexibility to manage around that. Even better if its a large one.

  • Moderators, Category Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 61,707 CMod ✭✭✭✭ unkel

    I've been saying it for years, well before the current energy crisis started. It's only a matter of time before we see the peak €1 per kWh. It now looks that might happen within the next year or two. Then a big battery will help to (totally) avoid paying that.

    @poker--addict - good point about the income tax. If it is income, you must be able to deduct expenses that were needed to make that income. If you have panels for export only, you must be able to deduct all of your cost of the install from the income those panels make and only pay income tax on the balance.

  • Registered Users Posts: 1,500 ✭✭✭ Manion

    Is Dyness pretty much the best option for a power wall? 10 year warranty looks very good. Does anyone know a installer fitting them?

  • Registered Users Posts: 396 ✭✭ zoom_cool

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  • Registered Users Posts: 1,186 ✭✭✭ poker--addict

    Aside from going all out and getting an asian total DIY job, what might I pay to purchase batteries from the likes of midsummer which i can link up easily to a hybrid inverter?

    Also what would be the best battery to get in this case? Is there any plug and play setups on alibaba?