Solar Bigger Expensive System for Feed in or Smaller Cheaper System with Battery?

LWoodOven on 31/05/2024 - 11:36

Hi all,

Looking at Solar for home, current bills are around $700 mark, was looking at a 10.6kW system with 24 panels or a 13.2kW system with 30 panels to offset useage and feed into the grid to lower overall electricity bill, coming in around the $10K mark depending on panels used.

Now someone has put the idea in my head to go a smaller 6.6kW system for less (around the $5.7K mark) and putting in a battery (unsure what they'd cost haven't made enquiries yet but would be mid range battery not a cheapo) under the premise that feed in tariffs keep getting lower and lower and the buy back amount is higher, plus the most expensive time to purchase electricity is the evening when the battery would kick in to offset it.

Now i'm lost and wondering if anyone can add any value to the battery argument, I know they're still not that cheap but it kinda makes sense what he's saying.

Thanks in advance!

Electrical & Electronics Solar Energy System

Comments

  • apple2016 on 31/05/2024 - 11:45
    +3

    Maybe add a poll ?

    I would suggest a battery (more so if you do qualify for a battery rebate) as feed in is next to nill these days.

    • dust on 31/05/2024 - 12:51
      +3

      as feed in is next to nill these days.

      It can even be negative, which is fun.

  • Ezekiel2320 on 31/05/2024 - 11:49
    +1

    Is your energy demand anywhere near 10kW? Feed in tariff is practically zero so unless you have massive ducted AC all over the house a 6.6kW system is generally overkill for everyone. 6.6kW and battery is probably better

    • Nugs on 31/05/2024 - 12:07
      +1

      "6.6kW system is generally overkill for everyone" except the middle 4 months of the year
      .

      • 2esc on 01/06/2024 - 10:27

        Why not go bigger and cover the middle 4 months with a bigger system? Especially with the way prices are going.

    • dust on 31/05/2024 - 12:52

      a 6.6kW system is generally overkill for everyone

      If you've got something like a pool pump, or electric heat pump hot water system I would disagree. Particularly during winter months.

      • Ezekiel2320 on 31/05/2024 - 13:27
        -1

        Pool pump: 2400W.

        HPHWS: 500W (2800W with resistive heat boost)

        Two "3.5kW" split systems: 2000W

        Still leaves you breaking even or better, even with the extremely unlikely 100% duty cycle estimate.

        Particularly during winter months

        So double your panels for an extra 10% generation? Uhh you might wanna check your maths again Spongebob

        • dust on 31/05/2024 - 13:31

          That's assuming you're generating with all your panels all the time, which is unlikely.

          • Ezekiel2320 on 31/05/2024 - 14:01

            @dust: Correct, about as unlikely as all your appliances running at max demand all the time. And yes like I said, in winter for example, when generation is, say, 20% of potential, 20% of a 6.6kW system = 1.3kW. 20% of a 10kW system = 2kW. Clearly not worth spending double on a system that will provide marginal benefit in a narrow slice of the year, and will be massively massively oversized any time that isn't cloudy.

            I'm glad you agree

  • KiKH on 31/05/2024 - 11:52
    +1

    get some quotes, and calculate the return on investment in years for each case. batteries usually add a few years to this.

  • geekcohen on 31/05/2024 - 11:55

    current bills are around $700 mark

    Per month or per quarter?

    • WoodOven on 31/05/2024 - 11:55

      Per quarter sorry

      • geekcohen on 31/05/2024 - 11:58

        That isn't bad. Mine were $1200 per quarter before solar. Now $750 with a 6.6kw system. No battery as cost is too much.

        I went cheap and it helps. Cost be about $3.5k out of pocket after Vic Solar Rebate.

        Might only last 10 years, but I only plan to be in the house for 5 to 6.

        • JimB on 31/05/2024 - 15:05

          Those bills are quite high.

          What do you run?

          Your usage higher in Winter or Summer?

          • geekcohen on 31/05/2024 - 16:44

            @JimB: WFH full time and have IT equipment running plus a few fridges. "Cold" usage overnight is about 1.5kw/h.

            My usage is definitely higher in winter (pushing $300 a month) due to heating and additional lighting (inside and out).

  • geekcohen on 31/05/2024 - 11:56

    offset useage and feed into the grid to lower overall electricity bill

    You pretty much get nothing back for feed in, you want to either store it or use it.

    • Joey2scoops on 01/06/2024 - 11:58
      +1

      in some cases there are penalties for feeding in to the grid.

  • dtc on 31/05/2024 - 12:05
    +1

    As others have said, you need to consider both the feed in tariff but also need to consider the time of use of your electricity. For example, if you use a lot of heating (live somewhere colder), then your electricity production via solar (day) wont match the timing of your electricity use (night). But if its mostly air con or pool pump etc then you will be able to mostly run it off solar as you are using the power during the day

    Hence in the former situation having a battery is more beneficial as you will be using power when there is no solar production, so taking it from the battery. In the latter situation, you fill up your battery but then may not actually use it overnight or only very minimal for lights and TV.

    All that said, you are 'saving' around 4k from the smaller system and the cheapest battery is at least $9k and that is small capacity https://www.solarquotes.com.au/battery-storage/cost/ . So it will be hard to make the numbers stack up.

  • nizzkid on 31/05/2024 - 12:08

    Just read that in NSW the power companies are going to start CHARGING you to export.
    WTF.
    Battery is my vote.

    • SBOB on 31/05/2024 - 13:49
      +1

      Just read that in NSW the power companies are going to start CHARGING you to export.

      they arent.
      The underlying network supplier (i.e. Ausgrid) will have a TOU structure associated with feed in tariffs.
      If you were on a plan getting 7c/kwh FIT, and there was a 2c/kwh export 'fee' during a time of day, you'd still be getting 5c/kwh FIT during that time.
      Retailers will choose how they structure their plans how they wish to offer them to the market, just like they do now.

      But shock jocks and click bait articles dont really explain it when 'getting charged to export' is a more appealing headline.

      • san87 on 03/06/2024 - 18:31

        I couldn't find any news article saying there would be a 1.2c/kwh fee which would be deducted from the feed-in traffic(AUS GRID). It looks like a negative feed-in traffic.
        Do have any links to share? Thanks

        • SBOB on 03/06/2024 - 20:35
          +1

          eg explanation article
          https://www.solaranalytics.com.au/community-news/export-char…

          In its modelling, the AEMC explored a flat export charge of 2c/kWh. If this were implemented by a network company and if an energy retailer applied it directly to your feed-in tariff, then your feed-in tariff would drop by 2c/kWh. So if you’re on 12c/kWh now, then you would drop to 10c/kWh.

  • TEER3X on 31/05/2024 - 12:12

    Interesting people are recommending batteries, when I was looking everyone advised against it, but I wasn't using as much as op.

    • FimpBARGAIN on 01/06/2024 - 10:05
      +1

      Was it installers advising against? I find none of them are interested in doing more than a standard install.
      The business model is to do install as quickly as possible, with the cheapest components and barely trained staff. Zero (profanity) given about cracked tiles or repeat business, battery and warranties just add complexity

      • cfuse on 01/06/2024 - 16:38

        Something to consider is that batteries are stupidly heavy. Who wants to blow their spine out when they can just skip those jobs entirely?

        Also I have no idea what the difference between the wholesale and retail pricing is for battery but I would suspect there's not a lot of profit built in there.

        • FimpBARGAIN on 02/06/2024 - 12:39

          There would be a bit, I've had access to wholesale prices for a few years waiting for rebates to come in for NSW. Maybe 20-30% mark up, but if it takes them another half day not worth the labour

  • nizzkid on 31/05/2024 - 12:13

    As for batteries being expensive, yeah they are. But, if your inverter supports it there are some very diy friendly plug n play batteries now. Could save a substantial amount going that way. Not sure of legalities though. And may not workout cheaper if there are government incentives.

  • nizzkid on 31/05/2024 - 12:18

    https://lifepo4.com.au/shop/lifepo4-battery/48v/5kwh/oem-eg4…

    @ $500 per kw/h.

    That's about half to a third of the costs listed in the link above.

    • freefall101 on 31/05/2024 - 16:08

      That doesn't matter much when you can't wire it up to your house.

      Replacement car batteries are closer to $150 per kwh, wholesale new ones are generally less than $100 per KWh. The problem is they haven't really hit mass production/adoption to really drive down pricing as part of the kit to attach to a house.

      Hopefully with Tesla sales dropping Musk will turn to home batteries instead to bolster revenue, or we finally get V2H happening.

  • Duckie2hh on 31/05/2024 - 12:50
    -1

    current bills are around $700 mark

    per month?

  • sane on 31/05/2024 - 12:55
    +1

    Battery - no question. Assume that the feed-in tariffs will go to zero (or negative) because the government is letting the power companies get away with it.

    You should know what your average daily consumption is already. Then divide that by 4-5 (average hours sun per day) and you should have the 'balanced' solar capacity needed. Add a battery to that which is 70% ish of your daily consumption and see where that lands on cost/RoI. You might find that pushing the battery size a bit (and/or solar) isn't much more expensive since the install cost is a significant proportion.

    Also consider some panels pointing west in addition to the north - to spread generation hours into the evening (at least in summer).

    • FimpBARGAIN on 01/06/2024 - 10:07

      Agreed, it's pretty clear at this point that you can't plan a 10+ yr install assuming there will be any feed in tarifs

  • brad1-8tsi on 31/05/2024 - 13:01
    +1

    I fitted my Solar PV last year (3rd system I've done at different places) and if I'd been smart enough to realise where FITs were going I would have added a battery despite the 12 year payback.

    If you have the cash then fit the 10.3kW with a small modular battery pack and add more as you can afford it.

    • LFO on 01/06/2024 - 11:26

      a small modular battery pack and add more as you can

      Spot on!

  • AustriaBargain on 31/05/2024 - 13:09

    Battery will let you heat and cool your home at night with split systems. It can be very nice having a house that is climate controlled 24/7.

  • geekcohen on 31/05/2024 - 13:55

    If you are in vic, this deal just got posted

  • w3dge on 31/05/2024 - 14:21
    +1

    I've had 11kw solar with a 10kw cheapo battery for a couple of years on originally roughly $1200 quarter bills. My solar will pay off this year, my battery is still looking unlikely to pay itself off by the 10 year mark, my bills are around $300 quarter now including car charging (don't drive much).

    Obviously depends on your electricity cost and usage, both my cars plug in at night so my battery doesn't last an hour.

  • spurf on 01/06/2024 - 09:38
    +1

    A Tesla Powerwall is around $15,000 and has a capacity that starts at 13.5kWh which degrades with time. Best case scenario you charge it everyday from empty to full, which will accelerate the degradation, you will save 4,927.5kWh a year. I'm on a flat rate tariff at 30c kWh so it would save me $1,478.25 a year although i would lose $345 of feedin at 7c/kWh. Payback is well over 10 years which makes it not worthwhile especially if you have a mortgage as you would effectively paid your current interest rate on that $15,000. Prices need to drop down a lot before it make any economic sense.

    • lgacb08 on 01/06/2024 - 09:55

      except your math won't be true in 2 years time, feed in will continue to fall and reaching zero, the savings will increase and if your know how to game the system you can use the battery to buy low and sell high to get extra before everyone catches up.

      • dtc on 01/06/2024 - 10:17
        +1

        Even if FIT is $0, that’s a $345 pa additional saving from the battery. Maybe makes payback 1-2 years earlier but it’s still along time

        And if your ‘hack’ is so profitable then as soon as many people do it then it will be shut down as well.

      • spurf on 01/06/2024 - 10:20

        That's possible but doesn't justify doing it now. The moment the money make sense I won't hesitate to install one. Also, what do you mean by buy low sell high? I though the feedin is fixed?

        • LFO on 01/06/2024 - 11:18

          Powerwall (Gateway) gives the option to "sell" when Tesla decides to.
          Never tried, still with a honeymoon FID.

      • LFO on 01/06/2024 - 11:24

        won't be true in 2 years time

        In particular if those dreaded charges for exporting too much power become real.

  • LFO on 01/06/2024 - 11:16

    If deciding for a battery system I will try to get away from Tesla Powerwall plus Gateway.
    They are absolutely excellent but are proprietary items.

    A previous thread mentions stand alone ones:
    Literally it states: 4 of these (deepcyclesystems.com.au) would give you 60kWh for $43K, pick up SE QLD, cylindrical cells, LiFePO4, service life 15-20 yrs.

    Not recommending, just mentioning. Get a big big system and then, later on and if ok, a non propriety battery.system.

  • bluyu2 on 01/06/2024 - 12:56

    I'd definitely get a battery, if you can. You may also want to consider a VPP, more info at https://www.solarquotes.com.au/battery-storage/vpp-compariso…

    For example, through the Shinehub VPP, you ge $0.55 per kW on top of the FIT from your energy provider. More is at https://shinehub.com.au/virtual-power-plant/

  • Waltervp on 02/06/2024 - 02:31

    Well I'm in Tasmania and get loads of sun in summer whwn i don't consume much myself and little in winter when i consume at least 40kwhr/day. That means in winter my battery would give me pittance and in summer wouldn't be worthwhile. Fortunately for me i get about the same in feedin tarrif from 1stEnergy as it costs to get off peak so i can't complain. These rates are available for anyone today. And with my pension discount i have always been in credit for last 4 years. I don't even have a gas connection any more. So a 10k battery to me would be a total waste of dollars as it would take me 15 years to get any value. Maybe if batteries come down one day it may be worth while.

    In fact in Greece i believe the government subsidises battery purchases so much that its almost free. The reason they do this is because it benefits the grid to have more decentralised batteries, less feedin, and less draw at peak times, and as far as the government is concerned no further costs to them.

    https://taiyangnews.info/greeces-solar-storage-funding-schem…

  • 5secondrule on 10/06/2024 - 23:23

    I'd suggest you do some calculations yourself before making a decision. Most of the time at present batteries are a poor investment with payback times far exceeding warranties. FITs are terrible ATM too and getting worse so I'd size the system appropriately and be cautious about getting a bigger system just for the sake of it.

    What you could do is just get the 6.6kw, maybe with a hybrid inverter and then look at batteries when the economics add up in your favour (e.g. even worse FIT, significantly higher electricity rates, cheaper reliable batteries).

    • WoodOven on 11/06/2024 - 08:28

      I was literally thinking the exact same thing on the way to work this morning! Thanks for that

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