Need Some Advice on if a 36 Panel Solar Setup Is Overkill

• 

  AustriaBargain on 12/10/2022 - 17:53

  +2

  What about fewer panels but add a battery to help with night time?

  • 

    Richmond Tigers on 13/10/2022 - 12:05

    ROI on batteries is rubbish, it would take years beyond the warranty to see any benefit.

    • 

      Euphemistic on 13/10/2022 - 13:43

      That’s gonna change with increasing power prices.

• 

  Drakesy on 12/10/2022 - 18:00

  36 panel 13.32kW system producing optimally 58kWh

  It really depends how expensive it is.

  I have a 6.6kw system that was $2500 off here a year ago and have found the payback not as fast as originally expected (WA) low feed in rates and power prices are relatively stable. 2 person household, covers our daytime needs easily.

  In Melbourne where the prices fluctuate a fair bit it might be worth it.

• 

  AndyC1 on 12/10/2022 - 18:34

  +2

  Do you have 3 phase power already in the house? If not, check as you may need it for the 10KW system.

• 

  thatonethere on 12/10/2022 - 18:39

  These days unless you have inherited some sweet feedin deal - you either need a battery or need to shift consumption to maxium solar collection times (eg washing/drying/pool filter+heating/house heating and cooling).

  For us the big difference was shifting the pool filter/heating so it only ran in peak sun collection times. Also heating/cooling the house during the day - previously we just left the house alone if we were out at work/school and heated it up in the afternoon/evening.

  One of the neighbours house was ruined by an LG battery (took the fire brigade 2 days to deal with it).

  • 

    dcep on 12/10/2022 - 18:47

    +1

    seems like battery fire hazard from home or automobile , still very real and no improvement

• 

  Euphemistic on 12/10/2022 - 18:48

  +3

  Don’t rely on feed in tariff. If solar supply keeps increasing the wholesale rate will drop significantly due to excess. If the wholesale rate drops enough you’ll only get minimal $ for the power you export, effectively wasting it.

  Consider a smaller system and batteries. Work out how to cut your current consumption.

  It’s hard to quantify overkill without knowing your consumption patterns and potential generation.

• 

  cheaplee on 12/10/2022 - 18:50

  +1

  I seeyn to remember the maximum inverter size that the distributor will allow for FIT was 5kW.

  I don't know if that was only Energex (QLD) or if it is a standard thing across the country, but just make sure they will allow FIT on a 10kW inverter if you are factoring that into your calculations.

  • 

    kipps on 12/10/2022 - 22:44

    It’s 5kw per phase normally. They probably have 3 phase power.

• 

  battler on 12/10/2022 - 19:45

  +2

  Your numbers do not stack. You will produce that 58kw between the hours of say 9am and 4pm. Your consumption will not correspond to your usage.
  The price to buy a kwh is about 5x the price received for feed in, so if you consume 12kwh at night (~30% x 40kwh) you need to feed in ~60kwh during the day.
  You need to offset cost/feedin of kWh, not consumption/generation of kwh
  All numbers approximate - I am just trying to provide the vibe, not accuracy.

  • 

    Richmond Tigers on 14/10/2022 - 10:51

    Ah yep, it took me a good while to understand this but I think I finally get it.

    So the 60kwh feed in would be 60 minus say the 70% daytime usage, which in my scenario would be 28kwh.

    Therefore I would only have 40kwh left to feed in, and the shortfall is the deficit I pay?

    • 

      battler on 14/10/2022 - 14:40

      for this example I will use indicativate (and not likely accurate) values of feed-in 20c/kwh and consumption $1/kwh (indicating the 5x price diff bewteen feed in and consumption)

      You produce 58kwh, during the day.
      You consume (0.7x40kw) 28kw during the day, leaving 30kwh to bet fed in, 28*20c = $5.60

      You evening usage is (0.3x40kwh) = 12kw, which at $1/kwh = $12 cost.

      $12 cost less $5.60 feed-in is net cost of $6.40 (per day)

      Back to your point "which would provide ample feed in during the day to offset any night-time usage and supply charge" you have not achieved this.
      Your 30kwh feed-in does not cost the cost of your 12kwh consumption.

      Again, all numbers indicative to give the vibe, not accuracy.

• 

  slowcoach on 12/10/2022 - 19:49

  I'm clearly biased. I have a larger system than that and it's paid for itself after 2.4 years. The price difference at the time was something like twice the price for three times the size. Seemed like a decent deal to me. I now have an electric car doing at least 3000km/month and my bill is still well in credit. No pool, but hot water has a relay to heat by solar. I put on as many panels as i could fit and it's been the best household financial decision so far. I’ve been with Origin and had 12 months of 20c FIT, which was great. Now on 12c. Origin are also happy to send a cheque - i don't think all companies are.
  Max 5kW per phase btw

• 

  kipps on 12/10/2022 - 22:17

  +1

  At 40kwh per day go the max system you can get. That’s serious usage. Work out how to load shift it to use the PV generation and you’ll be miles ahead.

• 

  Polt on 13/10/2022 - 13:30

  +1

  Go for it. Not excessive, like others have said don't just rely on the FIT, focus more on offsetting your use. Batteries don't really stack up yet but you are future proofing your house for when this changes in the future. My personal view is with the way federal and state policies are going we will see batteries being subsidised in the not too distant future.

  Solar Quotes has some good articles on exactly this question, the takeaway is that the iterative cost of installing extra panels when you're intially putting in the system isn't that large, but trying to add them later sucks.

  https://www.solarquotes.com.au/how-does-solar-power-work/how…

• 

  MITM on 18/10/2022 - 15:47

  Serious question. Can you turn off the hot water at the fusebox at night to prevent using the grid and turn on again in the morning to use solar panels all day long ?
  Surely the tank would hold the heat overnight for hot showers/washing etc. next day.

  • 

    indemnity on 24/10/2022 - 21:48

    Your idea has merit and is basically what happens.

    Operating in manual mode by switching circuits is possible, but painful.

    What any smart meter or solar panel inverter will do is have three power settings: solar power in, grid power in and off-peak in. Some will even have more settings.

    Hot water is important and it's almost always on it's own circuit. You always need to heat the water to prevent Legionella and other nasty microbes. First, it's going to pull from solar in. If the water isn't hot enough by the time off-peak starts, it will draw from grid off-peak in. Most likely a hot water unit never touches regular grid power in, unless you have a single rate power bill.

    OP has a swimming pool they keep heated. That sucks way more power than even a large 250L hot water heater.