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#2650456 9-Feb-2021 16:19

gchiu:

If you're a high usage household then it makes more sense because you send fewer kWh back to the grid.

You really want to consume all the kWh you produce and send none back because you only get a credit of 8c/kWh but buyback those same kWh at 30c/kWh.

That won't be hard in Summer, as you use a lot less power. So the savings are a much higher percentage as the denominator is low. Even the you are paying the grid till mid morning. Winter, well no, when you need it, its not there.

I think its an awesome piece of tech, but the use case is the reverse of what we need. My mate has 9.1 kW and a Powerwall. 50k. If I took 5% of that as interest or the opportunity cost, thats $2500 p.a. If I had his setup, and used every kW, all the time, my own powerbill is less, so I could never make it work, as my largeish house and solar HW costs me less. And remember, he will have high power bills in Winter, less a few kW he harvests most days, because in Summer he harvests a lot and can't use it. So his payback further declines as he gets just 8c for his 30c kW he created. Yes, he tells me about his Summer credits...

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#2653027 10-Feb-2021 13:47

What I think is inequitable is that we buy electrical units at 30c but if we return them, we only get a 8c credit.

What should at least happen is that we should be able to buy back any energy we exported to the grid at the price we got paid for it. In other words, instead of being paid a higher credit as used to happen for exported units, we should be able to buy back what we sold to the retailer at the same price. What other retail business is allowed to buy back something unused at 30% of what they sold it??

Then that means our excess summer production becomes available to us over the winter.

elpenguino

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#2653030 10-Feb-2021 13:53

gchiu:

What I think is inequitable is that we buy electrical units at 30c but if we return them, we only get a 8c credit.

What should at least happen is that we should be able to buy back any energy we exported to the grid at the price we got paid for it. In other words, instead of being paid a higher credit as used to happen for exported units, we should be able to buy back what we sold to the retailer at the same price. What other retail business is allowed to buy back something unused at 30% of what they sold it??

Then that means our excess summer production becomes available to us over the winter.

But that ignores that the value of something varies depending on when it is available.

Why should I sell you a tomato in July for the same price I bought one in January?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

gchiu

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#2653033 10-Feb-2021 13:58

The same applies to the energy we produce. By your argument we should be getting the spot price for the units we sell.

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#2653040 10-Feb-2021 14:32

I guess you would get the spot price if your array was producing megawatts. Small producers are probably seen as a nuisance but one that needs to be allowed for political purposes.

Your power company is getting the spot price for your excess, minus the payment to you. Is the net to the power company always positive?

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

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#2653041 10-Feb-2021 14:32

gchiu:

What I think is inequitable is that we buy electrical units at 30c but if we return them, we only get a 8c credit.

What should at least happen is that we should be able to buy back any energy we exported to the grid at the price we got paid for it. In other words, instead of being paid a higher credit as used to happen for exported units, we should be able to buy back what we sold to the retailer at the same price. What other retail business is allowed to buy back something unused at 30% of what they sold it??

There's a reason a lot of QLD has solar, and new uptake has dropped off. Use to have ~3K funding to put it up. And then near 1:1 rebates. But it got a bit too popular - that's gone to less than half over the last 5 years. And the funding drops every year.

https://www.canstarblue.com.au/solar-power/a-comparison-of-solar-feed-in-tariffs/

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gchiu

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#2653073 10-Feb-2021 15:33

elpenguino:

I guess you would get the spot price if your array was producing megawatts. Small producers are probably seen as a nuisance but one that needs to be allowed for political purposes.

Your power company is getting the spot price for your excess, minus the payment to you. Is the net to the power company always positive?

One solution would be for homeowners with solar panels to band together to form a virtual power company to sell their excess at the spot price.

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#2653231 10-Feb-2021 19:30

gchiu:

One solution would be for homeowners with solar panels to band together to form a virtual power company to sell their excess at the spot price.

I once proposed that every house gets equipped with solar, sort of a climate change, make a difference thing. Those more expert than me stated that its a "minor" effect, residential solar isn't a game changer.

gchiu

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#2653243 10-Feb-2021 20:01

There is a company https://www.ourenergy.co.nz/ that allows you to sell your excess solar energy to your neighbours but the website is very unclear as to how their model works.

There was also this https://www.afr.com/politics/perth-blockchain-power-trading-startup-takes-auckland-20160830-gr4q8b but who knows what happened there.

"Perth startup Power Ledger will sign up 500 solar households, schools and community groups in Auckland to its blockchain energy trading platform under a deal with New Zealand energy company Vector.

The trial will be the first commercial deployment of Power Ledger's peer-to-peer energy trading platform, which uses the blockchain technology that underpins virtual currencies like bitcoin and has the potential to further disrupt the centralised power "

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#2653244 10-Feb-2021 20:01

I honestly feel that the cost isn't the primary issue, the issue is the longevity of the components. Battery every 10 years, Panels every 15, most people aren't even getting payback of their investment in that timeframe. Though I guess if it was half the cost, the longevity wouldn't be such a big deal.

With a good portion of our energy from renewable sources, it would be good to see power cost drop.

I really want solar, it really appeals to me, but it just doesn't make sense the way it is.

gchiu

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#2653271 10-Feb-2021 21:31

Solar panels pay back is now by 8 to 10 years and should last over 25 years. A Tesla powerwall 2 is guaranteed to last 10 years but should last 15 years and lead carbon batteries should last 20 years.

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#2654378 11-Feb-2021 06:51

gchiu: Solar panels pay back is now by 8 to 10 years and should last over 25 years. A Tesla powerwall 2 is guaranteed to last 10 years but should last 15 years and lead carbon batteries should last 20 years.

Mate has a Powerwall 2 , 13.5kW, $15k before they went to 18k, not sure what they are now. He's on a night rate about 13c kWh. At 18k it needs 138,000 hours for payback. If it tops up during the day, 13 x 13c is $1-69 per day payback. 10,000 days, 29 years.

gchiu

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#2654411 11-Feb-2021 09:09

I also have a PowerWall 2 which cost me $13k installed. I know it gets used during the day when the house draw is higher than what the panels are producing at the time.

I don't have a 13c/kWh night rate. To get that I'd probably have to have an EV associated with the house.

But the night rate starts at 9pm and finishes at 7am. And power from the panels finishes at 5 - 6 pm so the peak time power comes from the batteries at 6-9pm.

And again at 7am - 9am which is before there is significant production from the panels. If there is no day time sun production then both the panels and battery are almost useless, except if you have a cheap night time rate, you can top up the battery from the grid the night before.

So, your calculation is flawed. And also doesn't take into account the effect of inflation. Nevertheless, it doesn't look like the Tesla PowerWall2 can currently pay for itself unless there's significant inflation in power costs.

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#2654425 11-Feb-2021 09:24

gchiu:

I also have a PowerWall 2 which cost me $13k installed. I know it gets used during the day when the house draw is higher than what the panels are producing at the time.

I don't have a 13c/kWh night rate. To get that I'd probably have to have an EV associated with the house.

But the night rate starts at 9pm and finishes at 7am. And power from the panels finishes at 5 - 6 pm so the peak time power comes from the batteries at 6-9pm.

And again at 7am - 9am which is before there is significant production from the panels. If there is no day time sun production then both the panels and battery are almost useless, except if you have a cheap night time rate, you can top up the battery from the grid the night before.

So, your calculation is flawed. And also doesn't take into account the effect of inflation. Nevertheless, it doesn't look like the Tesla PowerWall2 can currently pay for itself unless there's significant inflation in power costs.

If you had a night rate the calculation is about right. If you dont have night rate, the day rate is cheaper, so while you get more $ benefit from the powerwall at night you lose on the power consumed from solar during the day, less savings

To make any of this work you firstly need to be credited the full rate, not 8c, then you can timeshift Summer unused generation to Winter.

You would be better off to only install enough solar so that you use it all, forget the 8c credit as that just extends the payback fourfold. Then again, the smaller the install the more cost per kwH. That was my plan instead of tghe plan to get 7kW, but our roof is large but intricate so no room for more than 1.7kW at $9000. They then came up with maybe getting 3kW up there, but gain thats way too costly per kwH to consider it

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#2654478 11-Feb-2021 10:32

Last year I put in Powerwall 2 and LG Neon panels. In 10 years the panels will still be within 3% of now. Cost was not the issue (used the Westpac 10k interest-free for some of it). I built the best system I could to see what I thought. You gain on the capital value of the home and you also effectively live off grid which is a nice greeny feeling. I love my system. So far I am building up enough credit to cover winter bills. Best decision I ever made and zero regrets.

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