Solar Panels! Should I Use as Much of My Roof Space Possible?

• 

  salrock on 16/12/2023 - 23:30

  +1

  I would just install little above household usage but 30kw is a lot . What calculation you did for ROI ?

  The feed in tarrif is sh*t in vic not sure about Sydney

• 

  mskeggs on 17/12/2023 - 00:20

  +7

  30kW is a lot, and there is no guarantee feed in will stay reasonable. It could easily drop to nothing, especially during the middle of the day.
  A normal house uses about 22kWh per day. 30kW of panels producers around 120kWh per day. Unless you had a home battery and electric vehicles, as you state, the bulk will end up back in the grid.
  If I was starting from scratch, I would do all my heating and cooling via aircon, my hot water via a heat pump, and a battery to power the house at night - and I think 10kW would be plenty for that, and likely enough to charge an electric car for normal driving too.
  There is no obstacle to adding further panels later - you can have two inverters and two sets of panels if you add more later.
  If I was dead set on extra panels, I would seek to point a chunk of them west, so you are generating power in the afternoon - the need for power in the hours before sunset is likely to remain high, while demand earlier in the day is already well on the way to being met via solar (well, when the last few coal plants turn off there will be more demand needed, but in that time it is also likely there will be a lot more solar in the grid).

  • 

    donedeed on 17/12/2023 - 14:02

    Is there any recommendation on what brand to pick for hot water via heat pump?

    Battery, I'm considering the BYD on maybe in the next year or two. I'm waiting to see if the government will dish out some rebate.

    Sounds like 10kW is the sweet spot. I have an EV, but I would charge almost everyday using excess solar.

    • 

      mskeggs on 17/12/2023 - 16:54

      I’m not up to date on batteries, but I feel like there is a premium to pay at the moment. I suspect there will be a price drop over the next year or two. Would love to be proved wrong!

    • 

      Dogsrule on 18/12/2023 - 20:32

      +1

      Deon't bother with heat pump hot water systems - they are a scam. The 'cheap' ones (still damn expensive) are notoriously unreliable, and the reliable ones are way too expensive to ever break even on TCO. Additionally, they aren't very efficient in the dead of winter. Just buy a cheap resistive element storage HWS and run it off your giant solar system in the middle of the day using a simple cheap timer. It'll last 15-20 years, cost very little to buy and the lower efficiency is basically irrelevant because you're running it off solar.

      • 

        ATTS on 18/12/2023 - 21:08

        Can you add aftermarket " cheap timer" so hot water runs only in the day time?

        Sometimes my hot water spikes in the middle of the night

        When bought the house it already had solar hot water but i dont think it has a timer

        How much would " cheap timer" cost? And would we need electrician to install it?

        • 

          Dogsrule on 18/12/2023 - 21:27

          @ATTS: You sure can, but you do need an electrician to install it. The timer shouldn't cost any more than around $150 installed. The timers themselves are very cheap, like $35 or so.

          Keep in mind that I was referring to 'cheap' in the context of spending $3.5-6K for a heat pump HWS vs $1.5K for a regular HWS + timer.

          • 

            ATTS on 18/12/2023 - 21:33

            +1

            @Dogsrule: Ok thanks!

• 

  hashtagbargain on 17/12/2023 - 02:34

  +1

  But when reading on websites like solarquotes, they recommend installing the biggest system possible (if budget allows).

  Just imagine, a website that encourages solar adoption saying buy more solar.

  Personally, with the drop in feed in tariffs my recoupment plan has worsened. For many with older properties, there may never be a break even given how the trend is to punish solar panel owners with negative prices.

  Also want to mention that solar efficiency drops year on year - my panels have been producing lesser. Still not sure if it a climate issue or the nature of panels.

  • 

    Protractor on 17/12/2023 - 09:58

    -2

    Yep, nobody is doing for altruistic reasons.Bring on a solar panel tax with teeth.

    • 

      mskeggs on 17/12/2023 - 17:18

      Um, not sure it is a cut throat as this - plenty of people chose solar in the face of uncertainty and mixed economics because green energy is a good thing. Take a look as Renew magazine or similar to see evidence of plenty looking at it from a more ethical view.

      That said, I 100% agree that equity is crucial in addressing energy production, and the incentives and opportunities currently available favour home owners with roof space and aspect to benefit.
      Luckily, this is one of the situations where the market is beneficial - you can already sign up for a tariff with zero charge for energy use in the middle of the day, and that is a great opportunity for renters or people unable to install their own panels - if you are prepared to time the bulk of your consumption you don’t need solar panels to benefit.

      I’m probably (depends on the details) opposed to a blunt tax on solar. It would unquestionability favour fossil fuel energy producers, and my priority is prioritising distributed generation, even if it disproportionately rewards some people.

      We already have plenty of adjustments to support low income people, and there is scope to improve those while encouraging everyone who can support local generation to maximise it. Many people live in situations where they can’t contribute to the energy mix, but we can make adjustments to the way the system works to improve fairness.

      For example, I would love to see personal power generation arrangements - if I have a boomer parent with plenty of solar, but I live in an apartment, let’s allow us to pool our energy bills - the parents feed-in can offset the apartment energy use and cancel out usage, with maybe an increased supply charge to compensate for extra poles and wires, but not supporting a coal generator.

      And if you can do that, why not make a bigger market, where a person like OP who can support 30kW is able to trade their output with a stranger who is in an apartment. The difference being that instead of cementing fossil fuel generators place in the market, it makes it beneficial for everyone who can install solar to do so, and those who can’t to also access the benefits without a big generator involved.

      That provides incentive for more clean energy, while supporting people being able to choose the type of housing that is most beneficial to them.

      • 

        Protractor on 17/12/2023 - 21:57

        -1

        Is there not enough energy, not enough cheap energy, too many users,too much greed or all of the above?

        The simple fact is there's too many snouts at the limited number of troughs, and the irony of people wanting to not only break even but come out in front from solar, tells me they have already opted into the energy production market, and should pay taxes and whatever other charges required . The reality is the govt could and probably will step in and have mandatory annual safety inspections of all people making money from solar, Ergo a tax on energy production dressed up as safety. Which is equitable when you think of non solar users,who have to maintain a safe on property meter pole and and infrastructure (on their property) by law.
        We could and should have had a gas/renewable grid 25 years ago. Via converting all coal power stations to gas as a bridge to solar storage with gas boosting for peak events. Big fossil fuels control both sides of our govt,state and federal. And that's another way of saying (as always) we are Americas bitch.

        TLDR: At the beginning of the rooftop solar boom there was a less greed driving the process.There was a higher % of environmental motivation and concern.That came from poor planning and governance ,but mainly from the usual selfish human endeavour, of 'me first'.

        This is the mess the LNP gave Australia. And beyond. Much like the NBN, but more existentially perilous in the big picture. Labor is also culpable for "politically fellating" the CFMMEU as a default position.

  • 

    1st-Amendment on 17/12/2023 - 15:24

    +1

    my panels have been producing lesser

    Do you clean them?

    • 

      hashtagbargain on 18/12/2023 - 05:10

      Yes they’ve been cleaned, didn’t make a difference unfortunately.

      • 

        1st-Amendment on 18/12/2023 - 10:45

        They do lose efficiency over time, about 0.5-0.8% per year. UV kills everything and Australia gets a lot of it.
        What sort of percentage losses are you seeing?

• 

  lgacb08 on 17/12/2023 - 06:06

  +1

  Yes, but your place is significant larger than a typical house on solar quotes. Also you need to review your roof layout and surrounding shades, you might find the good usable portion might not be that much to fit in 80+ panels.

• 

  caboose on 17/12/2023 - 07:19

  It's good to oversize a bit more than required for your typical usage to account for diminished production on cloudy/rainy days.

  That said 30kW of panels is a huge amount. We filled out our roof and were only able to get 8kW of panels.

  • 

    Sal in SA on 17/12/2023 - 09:11

    6kw and used less than 1/4 of roof (existing install), can only imagine how small the roof is for only 8KW.

    • 

      caboose on 17/12/2023 - 13:31

      Yeah, relatively small house combined with a flat roof requiring tilt frames which need 1m spacing between rows to prevent shading.

• 

  JIMB0 on 17/12/2023 - 07:52

  Fill up the east, north and west roof faces that don't get shaded. Make a decision from there.

• 

  AngoraFish on 17/12/2023 - 10:16

  +1

  Beyond covering your normal daily usage your payback period starts to significantly blow out the more solar panels you add. This is pretty clear when you plug in different scenarios into the various solar break even period calculators out there. This is because at peak periods your extra panels are doing nothing other than feeding into the grid for a marginal return, while in shoulder periods/at night/when it's overcast your extra panels are operating at a fraction of peak capacity, if they're generating anything at all.

  When using calculators be wary that more common ones typically assume a floor price on feed in tariffs that is more than you can currently get in most states, and it's gone down just about every year since feed in tariffs were invented, they have never gone up - in fact, there is a lot of buzz about even charging you to feed into the grid in peak periods because the network is already getting more free power at those times than the grid currently has capacity to accept.

  Personally, I reckon that you're wasting your money buying anything beyond your typical peak household use with a 30-50% margin to pick up shoulder times and future growth in household use.

  Also, you need to base your usage calculations on peak hourly use during the day when it's sunny. It's useless using a standard household bill average daily KwH total for this because much of your typical daily use will be generated in the mornings and evenings when solar panels are either operating well below capacity, or not at all. Comments (and calculators) that talk about "typical daily household use" are misleading - without a battery a large percentage of your household electricity is going to continue to be bought from the grid regardless of how large your solar system is. Solar panels will also not change your daily supply charge.

  Larger capacity can also mean a more expensive inverter, and inverters have a much shorter effective lifespan than the panels themselves - typically 10-15 years, after which it will need to be replaced for a similarly relatively more expensive one. Indeed, additional expenses, such as replacing the inverter and 2-5 year servicing of the system are rarely if ever included in calculations of payback periods.

  • 

    donedeed on 17/12/2023 - 14:04

    I'm looking at the Fronius Gen24 inverter plus. In case we get a battery in the next year or two.
    Will these only last 10-15 years too?

    I think I will stick with a three phase 10kw inverter. I think anything bigger will be redundant from what I'm reading.

    • 

      mskeggs on 17/12/2023 - 17:29

      +1

      Panels will produce for a long time, hence the 20 year warranties.
      Inverters and batteries, less so. My rule of thumb is to expect to replace both within 10 years. History suggests some cheap and cheerful inverters die after 5 years, but costlier last longer.
      Batteries are still a bit in question, in my opinion. Are there any battery suppliers who haven’t had some issues over 5 or 10 years? I have a friend with a power wall from day 1 still going well but there have been lots of recall type issues for batteries in general.

      I reckon* (*reckoning being the Australian tradition of weighing it up without maybe all the evidence) that it isn’t worth paying extra for the possibility of adding batteries later - either get them now, or reassess the whole question when the time for batteries comes around and you are ready to act.
      It would suck if regulations change, or a new player comes in much cheaper but you are locked in to an older technology.

• 

  narbe on 17/12/2023 - 11:16

  I think the first port of call is to join MEEH(FB group) and then correlate with information on solar quotes.

  I recently took on this task in the same situation as you, fresh new build.

  I ended up with 13.3kW system with a consumption monitor included at $8k with a platinum installer in QLD. No battery and no hybrid inverter. (price-match FB ads)

  Filled up North first and East first. Saving West for later (have slight partial shading on West from flame trees (council).

  Purely based on ROI I think this is the best to go, as future proofing isn't exactly great without good tariffs these days. Self-consumption is king which means using the solar during day time , if you work during the day and weekdays then your self-consumption will be weak.

  However weekends you can kick back and relax air-con/heating without a thought.

  Reason I left west-side open is for future V2H battery option. When EV get to the stage where 1 week commute is easily covered and only recharge on the weekend, and EV doubles as a battery is when I'll fill up West.

  Self-consumption savings is a bit of variable , I like to think of it as more convenience of being able to turn air-con on during the day without a thought. Hot-water (1/3) of usage and other appliances ie. dishwasher and washing machine are true savings if you use during day. Air-con is luxury depending on your usage. (We usually turn off the air-con after 2hrs)

  • 

    donedeed on 17/12/2023 - 14:06

    Which solar panels and inverter did you go with? At $8k for that size is pretty cheap.

    I got quoted $10.5k for 10kw REC panels and solaredge inverter. I think this is pretty cheap considering the panels are just about the best you can get. The inverter I want to get the Fronius Gen24 plus instead though.

    • 

      narbe on 20/12/2023 - 12:33

      seraphim bifacial + sungrow inverter.
      From memory fronius was 1k more.

• 

  Euphemistic on 17/12/2023 - 11:28

  You should aim to be using or storing all the power you generate. Don’t aim for ‘making money’ from excess generation.

  Work out what you current household usage is. Allow some extra for cloudy days and future proofing eg EV charging, shutting off gas and going full electric etc. be realistic with EV charging too, you won’t need to generate 400km worth of range if you work from home or only travel 20-30km each day.

  Get a solar system sized to your needs.

  Our system generates about what we use in summer, but falls short in winter. It is however quite a few years old and I’ve been contemplating how we might increase it.

  • 

    donedeed on 17/12/2023 - 14:07

    Yes, I completely agree.
    I'm going full electric and disconnecting gas altogether.
    It's just a bit hard to justify the cost of battery at present.
    I will monitor our usage over the next 12 months and see if battery can be justified.

    • 

      Euphemistic on 17/12/2023 - 14:30

      Was told by someone in the industry that batteries aren’t a financial decision at present. The payback period is too long. Solar is good, batteries are good, but only if you are off grid or just wanna stick it to the spark vendors.

      • 

        mskeggs on 17/12/2023 - 17:40

        I think batteries pencil out as neutral financially. You swap possible interest on the cash in the bank for 10 years against insulation from power bill changes.
        I see lots of older people who might be on a part pension or similar deciding they value the predictability of spending the money today as useful, because it insulates them against both power bill swings and also changes in rules for how much money you have for getting the pension (you get a little bit more pension if you are $10k poorer, and you know your power bills will be much smalller too).

        • 

          Euphemistic on 17/12/2023 - 17:57

          +1

          @mskeggs: Pension and financial assets would certainly seem to alter the equation.

          I asked the simple question ‘worth getting batteries yet?’ And got a very quick response of NO. Said industry person also doesn’t have battery on their own house despite being fairly well off, having access to ‘staff discounts’ and generally looking to be a bit less of an impact on our environment.

    • 

      mskeggs on 17/12/2023 - 17:36

      +1

      Worth remembering a 5kWH battery that gets 100% use every day has predictable finances, while a 12kWh battery that doesn’t get 100% duty cycle has considerably worse economics, even if you are leaving a few dollars on the table on the days you do 100% use it.

      I’m really conscious of human nature. If you have a tight power arrangement, solar and a little battery, your daily incentive is to conserve power and be cautious. If you over spec, the acid is off, and you don’t worry about timing and conserving.

      Of course, maybe your circumstances are an extra $10k now to not have to think about it might be a worthwhile improvement of your lifestyle!

• 

  AustriaBargain on 17/12/2023 - 11:39

  You might buy a big battery system one day and then you can blast your climate control at night?

• 

  Drakesy on 17/12/2023 - 12:32

  +2

  Don't aim to make money from exporting, it doesn't work out.

  IMHO a 6.6-10kw system is the sweet spot, anymore and the payback period blows wayyyy out.