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gchiu

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  #2054702 12-Jul-2018 07:16
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I'm going to sign up for the deal. I am not going to have $30k tied up on plant on the roof, and it's going to only cost me $120/month for 20 years for 60% of my power usage. Sure I don't own anything at the end, but if I pay my electricity provider I don't anything there either.

And if I sell the house, it will be an asset not a detraction from the price.

Could power prices drop? Anything is possible but I've not seen that in my lifetime yet. And in that unlikely case, I'll just start crypto mining to use up some power while heating the house with the heat from the CPUs!

 
 
 

Trade NZ and US shares and funds with Sharesies (affiliate link).
tdgeek
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  #2054708 12-Jul-2018 07:49
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gchiu: I'm going to sign up for the deal. I am not going to have $30k tied up on plant on the roof, and it's going to only cost me $120/month for 20 years for 60% of my power usage. Sure I don't own anything at the end, but if I pay my electricity provider I don't anything there either.

And if I sell the house, it will be an asset not a detraction from the price.

Could power prices drop? Anything is possible but I've not seen that in my lifetime yet. And in that unlikely case, I'll just start crypto mining to use up some power while heating the house with the heat from the CPUs!

 

I'm going to re read this thread to get a handle on it

 

You will pay $120 per month, for how much kWh panels? And battery?

 

How much will you pay for the generated power?  And for grid power?

 

 


Aredwood
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  #2054711 12-Jul-2018 07:53

Power prices definitely dropped for me when I moved from Contact to Flick Electric. And I'm now on a low user fixed price plan with Meridian, that is only approx 1c per unit more expensive than what I was paying for standard user with Contact.

And some of that increase is due to me having to go onto an anytime plan instead of controlled hot water plan, after I left Flick. Because I switched to a peak / offpeak plan while I was with Flick. No other companies offer that plan. And the controlled hot water plans in my area are grandfathered.

There was also an MBIE study that showed a drop in power prices.

Edited to add

$120 per month fixed fees. For some people that would be a major negative for buying a house. My most recent power bill is $127. And my parents only rarely get a power bill for more than $100 per month. And their house is electric only.







gchiu

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  #2054760 12-Jul-2018 09:21
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My last 3 monthly bills were $251, $344, and $268 with some days no one was even home.

 

And I have an Energy Smart hot water cylinder from Rinnai.  Now, Rinnai have had to change the control board 3x now but that should no longer happen now that that bad batch of boards has gone.

 

If I can reduce that under $200 I'd be happy.  And I'm replacing my wood burner ( open fire ) to ULEB shortly so my heating bills might even drop further.

 

The $120 monthly fee includes a green "rebate" of $75.


gchiu

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  #2054949 12-Jul-2018 12:25
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Oh, and the panels are Canadian 295 ( number to be determined ) and a Delta 6kwh battery inverter.


Aredwood
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  #2055408 12-Jul-2018 22:38

gchiu:

My last 3 monthly bills were $251, $344, and $268 with some days no one was even home.


And I have an Energy Smart hot water cylinder from Rinnai.  Now, Rinnai have had to change the control board 3x now but that should no longer happen now that that bad batch of boards has gone.


If I can reduce that under $200 I'd be happy.  And I'm replacing my wood burner ( open fire ) to ULEB shortly so my heating bills might even drop further.


The $120 monthly fee includes a green "rebate" of $75.



Unfortunately you can't do PV diversion on those so called smart cylinders. And you would be mad to not get PV diversion fitted to a solar + battery system. As you can use the hot water cylinder as a very large battery. Which in turn means that you can self consume more power. And import less grid power.

Install a second element to your cylinder as well, if the cylinder has an upper element port.





gchiu

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  #2056221 14-Jul-2018 17:46
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Actually the Rinnai smart cylinder has 3 modes, holiday, IQ mode and manual mode.  So, the manual mode operates like a traditional hot water cylinder.

 

See https://rinnai.co.nz/Product/121/257/water-heating-hot-water-cylinders-rinnai-smart-cylinder-the-rinnai-smart-cylinder

 

I did ask Solar City about diversion to the HWC but I think the people I spoke with didn't know anything about it.  I need to speak to one of their techs at some stage before the install date.




Aredwood
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  #2056223 14-Jul-2018 18:03

Those diversion controllers work by quickly pulsing the element on and off, and changing the ratio of on time vs off time. As a means of balancing solar output with the total load of your house. Such a pulsed supply is no issue for a restive heating element and a mechanical thermostat. But is completely unsuitable for any kind of electronic device.

Also a diversion controller and the smart cylinder controller are intended to do pretty much opposite things.





gchiu

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  #2056234 14-Jul-2018 19:41
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I can ask Rinnai, but in manual mode I can set the temperature to 65 ( or even 70 deg ).  I can't see the point in heating the water up higher than this as there is a risk of burning users.  And I guess I can change that at night to 50 deg, or even turn on vacation mode at night.  That way the heating is done during the day.


gchiu

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  #2056272 15-Jul-2018 09:26
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I had another look at the specs.  Mine is the 180 litre cylinder, and it says that it can raise the temperature from 15 to 60 deg in 3 hours using its 3kW heater.  If I were to use the shower in the morning, and were to drop the cylinder temperature from 60 to 50 deg, then the smart cylinder in IQ mode will attempt to raise it back to 60 deg only before I shower at night.

 

So, if it uses 9 kWH to raise the water temperature from 15 to 60 deg ( 45 deg ), then it's going to only use 2 kWH to raise it from 50 to 60 deg.  At night time there will be no PV production so it could draw that power from the battery which has been charged during the day.  And it could do the same thing in the early hours of the morning if there's a morning shower.  So, more than half of the battery storage is used for heating the water.

 

This seems like a very expensive use of the battery.  The Rinnai I think can be dumbed down by removing the smart controller.  I wonder if that's what I need to do?

 

As I understand it the solar diverters just send excess power to the heating element.  So, if there's an excess of 1kW being produced, that's what they send to the 3kW heating element.  I haven't read anything yet about pulsing.


Aredwood
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  #2056316 15-Jul-2018 09:57

gchiu:

 

As I understand it the solar diverters just send excess power to the heating element.  So, if there's an excess of 1kW being produced, that's what they send to the 3kW heating element.  I haven't read anything yet about pulsing.

 

 

The pulsing is the method used to send just 1KW of power to a 3KW element. (continuing your example) Otherwise, the element could only ever draw 3KW or 0KW. Which in your example, will result in either importing 2KW, or exporting 1KW.

 

The system should be setup, so that solar generation first gets used to directly power loads and recharge the batteries. When the batteries are fully charged, the divertor should then start sending power to the cylinder, instead of exporting that power. You then try to heat up the cylinder as much as possible, using diverted power. To reduce the likelyhood that you might need to import some power to help keep the cylinder hot.

 

Your cylinder should also have a tempering valve installed. So that even heating it to 80deg or so, the water temp at your taps will still be 55deg. And higher cylinder temp = more energy stored.






gchiu

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Aredwood
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  #2056488 15-Jul-2018 15:46

Is that the diverter model that you are considering getting?





gchiu

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  #2056534 15-Jul-2018 16:19
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No, I was just looking for an explanation of how the diverters worked.

 

What models do people use in NZ?


gchiu

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  #2061807 24-Jul-2018 16:59
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Well, Solar City have cancelled the install for the moment.

 

Seems that they can't decide on what clamping system to use on my vertical seamed long run roofing iron.

 

I don't really understand the issue .. there seems to be lots of different non-penetrating clamping systems available. 


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