Solar options for home in 2022.

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billgates

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#300644 24-Sep-2022 20:43

Hello folks,

We are in a 2-year-old house build so the coloursteel roof has plenty of life left in it. Our house design is a H shape, so we have a 23M long straight high pitch roof in one part of the house and 15M long straight in another part of the house with both sides of roof facing North with no shade at all which is a bonus. We are with Genesis on a recently signed 2 year contract for electricity + natural gas. Only hot water is on natural gas. Cooktop is up to 11kW induction, balanced pressure ventilation system with summer bypass mode and heat exchanger is integrated with ducting for aircon as well. We have a ducted aircon that's 14kW cool and 16kW heat with no zone control.

Our average daily electricity usage is between 50kW to 60kW, and average monthly is between 1100kW to 1400kW. I have been checking our daily and hourly usage in the Genesis app/website and most of our usage is at nighttime between 10PM to 8AM that is 95% ducted aircon averaging between 5kW to 7kW every hour. Ventilation system uses 0.50kW every hour. The monthly power bill only is between $320 to $350. We do not have an EV but the next car will likely be one which is likely atleast 5 years away. Both me and wife work from home 3 days a week.

The wish is to bring the power bill down from $320 to $50 per month or lower with solar and selling excess back to the grid. Genesis does offer 12c/kW for export back to grid. Lines company is Waipa networks.

I have contacted 4 installers in our area incl Harrison's to come and provide a scope and quote. 3 of the installers will be visiting next week with Harrison's is so busy that earliest appointment they had was 12th of October. We have applied for Westpac's 5-year interest free $40k loan for Solar and waiting to hear back from the bank as well which should not be an issue.

From the research I have done, I have come up with below possible solutions. Can you please provide your knowledge if these solutions are worthwhile or recommend an alternative. I am thinking that because we use lot more power at night, we need a setup with battery and that a single 6kW inverter with 9kW of panels + 15kWh battery will be a good starting point? I am hoping that both solution 1 and solution 2 will be $15k or under. I am specifying BYD batteries because they are Phosphate Iron with no Cobalt so zero chance of fire/explosion and they provide slightly more kWH than Tesla Powerwall 2 for same price.

Solution 1 - SMA 1 x 6kW Sunny Boy inverter, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). I could then in 2 years' time or break my Genesis contract now (will cost me $150 or $200) to move to a higher daytime rate plan but much cheaper nighttime rate plan to offset ducted aircon costs during night? Currently we pay flat 24cents/kW incl GST - 15% discount.

Solution 2 - Fronius 1 x Gen 24 Plus inverter, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). The benefit of the new Gen 24 Plus inverter is that they have a much bigger heatsink with fan and has up to 3kW PV point connection in case of a blackout, but I believe this feature will only work with battery storage and that during a blackour in daytime, solar panels along cannot provide power to this PV connection?

Solution 3 - SMA 1 x 6kW Sunny Boy inverter, SMA 1 x 8kW Sunny Boy Island inverter, 1 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). While this battery storage will not take care of all energy needs for nighttime duties, it should reduce the on-grid usage by 70%? I am hoping this solution will cost under $35k. The big pull for this solution is that in the event of not only a blackout but an extended power outage from grid, the Island inverter can then power up the entire home using panels in daytime while also charge up the battery storage if I am correct?

Solution 4 - Fronius 1 x 6kW Primo inverter, Victron 1 x Multiplus-II 48/5000/70-50 230V inverter, 1 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). The Victron Multiplus II is $2k cheaper than SMA Sunny Boy Island inverter. I am hoping this solution will cost under $35k. The big pull for this solution is that in the event of not only a blackout but an extended power outage from grid, the Island inverter can then power up the entire home using panels in daytime while also charge up the battery storage if I am correct?

Solution 5 - SMA 1 x 6kW Sunny Boy inverter, SMA 1 x 8kW Sunny Boy Island inverter, 2 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look). I am guessing this will cost just under $50k. I am happy to spend the extra $10k from pocket and this 30kWH will likely keep me off grid for most days of the year if I am not wrong?

Solution 6 - Fronius 1 x 6kW Primo inverter, Victron 1 x Multiplus-II 48/5000/70-50 230V inverter, 2 x BYD LVL Premium 15.3kWH battery, 22 x 420W (9.2kW) REC Alpha Pure panels (for all black look) or 22 x 420W (9.2kW) Q-Cell Q-Peak Duo G10 (for all black look).

Solution 7 - SMA 2 x 5kW Sunny Boy inverter, 30 x 420W (12.6kW) REC Alpha Pure panels (for all black look) or 30 x 420W (12.6kW) Q-Cell Q-Peak Duo G10 (for all black look). I double up on the inverter and add more panels to maximize sell back to grid and when we have more $ down the track, add the islander inverter/charger and battery later. I am hoping this solution will cost under $30k.

Solution 8 - Fronius 2 x 5kW Primo inverter, 30 x 420W (12.6kW) REC Alpha Pure panels (for all black look) or 30 x 420W (12.6kW) Q-Cell Q-Peak Duo G10 (for all black look). If I am going to add the battery later for my solution, then I do not want to go with Fronius Gen 24 Plus inverter as it would mean then I would need to buy BYD HVS or HVM battery (400V) which costs more than their LVL Premium (48V). I am hoping this solution will cost under $30k.

Below is current month's ongoing electricity usage.

Below is a day's hourly usage breakdown with aircon running through the night.

Do whatever you want to do man.

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262 posts

Ultimate Geek

#2972647 24-Sep-2022 21:44

Looking at your power profile I think you'll probably need to move power companies to make solar work optimally for you. Probably combined with replacing the gas hot water with electric hotwater and a solar diverter or timer to improve your power usage and get rid of the gas connection fee (assuming mains?) and the cost of gas. Ideally something like Octopus or Electric Kiwi move master where night rates are about half of the peak rate, and where there solar buy back (17c and 14c) is in some regions higher or equal to the night rate, effectively meaning for every 1kWh you export you'll trade it 1-1.1kWh overnight.

If we look at how a 9kW panel system on a 6kW inverter will do your probably looking at ~12,000kWh a year (assuming Auckland, changes a bit depending on where you are in the country) with an average of >40kWh in summer and >15kWh in winter. However, you could be generating 6kW pretty solidly between 10-3 for maybe 30kWh of generation but your usage looks to me more like 6-7kWh, so ~24kWh will either need to go into the battery or be exported. With a purely north facing system your generation will likely not cover you usage in the early morning or evening. One option that can help there is to have some of the panels facing east and west (if possible) as it spreads out the generation into the early morning and evening and this would better match your usage.

With regards to the Fronius Gen 24, the PV powerplug they provide will work as long as there is sun even if the power is cut. This does not require a battery, but the power is limited to the lower of 3kW from a single mains plug or what ever the solar panels are producing if it's less than 3kW.

With your usage profile a battery would certainly help if you change to a plan with peak and off-peak charges (still may not pay for it's self in warranty period though) it would allow you to use your solar to cover the 4-5 hours after sunset which is one of the two peak periods.

Secondly does your house have two or three phase power? If it's a typical single phase supply options 7 and 8 are unlikely to work, as for a good part of the country you are limited to exporting 5kW of power per phase. With 2x5kW inverters you would have the potential to export close to 10kW, and thus they will either not install two inverters, or they will limit each inverter to exporting a max of 2.5kW meaning once your battery is full which would happen in 3-4hrs at which point all your excess solar would be lost as the inverter would not generate it.

The problem with your massive night time use, is that a standard 10-15kWh battery is going to be used up by midnight. You would need 2-3 batteries that size to cover the majority of your night usage, and that will likely cost >$30k just for batteries, not to mention the 12-15kW of panels and inverters you would need to charge the battery.

If I were you I'd probably do the following:

Get rid of the gas connection for the hot water (unless it's bottles), the savings from the removal of the mains connection would be noticeable, replace with electric cylinder and timer or solar diverter the solar will supply all your hot-water.
Get 9-10kWh of panels + a 7 or 8KW inverter (typically the recommendation is more like 1.3x the inverter size, not 1.5x)
See if you can get 4kW of panels split to face east and west rather than due north to extend the solar day and the breadth of you solar export generation, the rest of the panels face north
Add a 15kWh battery, and program it to only be used in emergencies or during peak times 7-9am and 5-9pm
Break the Genesis plan and move to either Octopus, Electric Kiwi Move master, or possibly Flick electric, as they all have lower overnight rates
1. If you go with Electric Kiwi, set the free hour to early evening and program the battery to top up during it, or at what ever time your AC system turns on that's using 5kW + set the battery to charge at that time, then use battery during peak periods where there isn't enough solar
2. If you go with Octopus, charge the battery over night, then during the day export as much power as possible, and use the battery to cover the peak times when there isn't enough solar (assuming the overnight rate is less than the solar rate in your area)

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billgates

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#2972673 25-Sep-2022 09:37

Thanks @eonsim for a detailed reply. Below are answers to your queries.

1. We live in Cambridge so come under Waipa networks for electricity. Waipa networks mentions 10kW export is ok with them as per their standard application form from the looks of it with a $200 application fees but if you want to export more than 10kW and to maximum 100kW then there is an initial approval that needs to made followed by a second approval and that costs $500. We are happy to submit the standard form for up to 10kW which I believe the installer will do as part of any distributed generation install they do.

2. We have 2 phase coming into the house but IIRC, only our induction cooktop is connected to it as it can suck up to 11kW at its max load. We only pay for 1 phase power though as I have never seen any extra billing amount for second phase and we only have 1 meter in the house. Can that 2 phase cable help with more potential for the solar setup specially with 2 x inverters if we go with that setup?

3. Long term (I am thinking 2 to 3 years), we may get rid of gas hot water if we find plenty of capacity left in our solar system to distribute. We spent close to $6k 2 years ago for gas pipe being run during house build, compliance certificate, gas califont, controllers in bathrooms etc so want to get more return from this before trying to sell the califont and controllers on trademe. We currently pay usually under $50/month for gas bill of which $30 is connection fees alone.

4. Good point on putting some panels on east for early and late morning sun. We have same length of space on other side of roof so no issue with location or shade.

Do whatever you want to do man.

eonsim

262 posts

Ultimate Geek

#2972742 25-Sep-2022 13:40

Not to far from me then (Hamilton), there are a number of people in the local area that share solar data from 5-11kW systems so if you want to see the sort of performance that you can get in the Hamilton area have a look at the following links they'll give you an idea of actual generation, per day and month.

https://pvoutput.org/list.jsp?id=95083&sid=83894

https://pvoutput.org/list.jsp?id=99706&sid=87796

https://pvoutput.org/list.jsp?userid=96957

With your usage your 10-12kW of panels options on either a pair of 4-5kW inverters or a single 8kW inverter probably make more sense if your allowed to export up to 10kW. Dual inverters may be a bit more flexible with allowing you to spread your panels around East, West and North.

If you've got a two phase setup then you would only have one meter (and it's potentially 3-phase but your only using 2), there is no extra charge to use a 2 or 3 phase setup compared to a one-phase just may have cost a bit more to have installed due to the extra cable. The problem with multi-phase setups is power exported on one phase can't be utilized by the other. So if you had two 5kW inverters one on each phase, then the first inverter would cover the house load as long as it wasn't more than what ever it's currently producing, while the second inverter would be exporting all the power on the second phase unless the induction cooktop is on. Thus usually either all or the majority of the solar will be put on the main house phase to cover your normal load, or when the solar is installed with two inverters the house hold circuits will be split up and redistributed between the two phases to try and maximize the utilization of the load.

Jase2985

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#2972789 25-Sep-2022 18:23

unfortunately your usage patterns dont do much for helping you in trying to save what you want to save, and i think its overly ambitious to think you could reduce your power bill by that amount. your heat pump will drain a 15kwh battery in about 4 hours. this continual draining of the battery will make it fail quicker.

how much power can you shift to daylight hours? and why the need to use the heat pump so much at night? is the house not well insulated? is there things you could do there to reduce the power used buy the heat pump?

Mark

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#2972965 26-Sep-2022 10:41

Swap your induction hob for a gas one and you'll drastically bring down your power bill :-) Plus it wouldn't be fun trying to do an inverter setup to run it.

Are you sure you can be bothered selling back to the grid ? You'll only get a buy rate of $0.06, which is really not worth bothering about to me.

My house is a high power use house (family of 5 with kids who leave lights on all over, heat pumps, me in IT with too many computers about and an EV on a 15amp plug), in the past month we've used 1300kWh. Only 61kwH of which was from the solar and we've only exported 24kWh back to the grid.

System is 3kW of panels, 10kW of battery from Vector. When full and off grid it can power the house essentials (water pump, lights, internet, selected sockets and fridges/freezers for a day, and in summer could probably keep up without the grid)

Past 12months we have exported a grand total of 602kWh for a profit of $36 .. yay.

You might be better looking at investing in a good battery bank and then sizing the panels to keep it fed.

Ge0rge

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#2972977 26-Sep-2022 11:25

Mark:
Are you sure you can be bothered selling back to the grid ? You'll only get a buy rate of $0.06, which is really not worth bothering about to me.

As mentioned above, Octopus buy back at $0.17, and charge $0.15 overnight - export everything you can during the day, charge your batteries at night.

billgates

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#2972998 26-Sep-2022 13:00

Jase2985:

unfortunately your usage patterns dont do much for helping you in trying to save what you want to save, and i think its overly ambitious to think you could reduce your power bill by that amount. your heat pump will drain a 15kwh battery in about 4 hours. this continual draining of the battery will make it fail quicker.

how much power can you shift to daylight hours? and why the need to use the heat pump so much at night? is the house not well insulated? is there things you could do there to reduce the power used buy the heat pump?

Home is well insulated, but we have large glass joinery across the home which gives us a lot of daylight everywhere. The ventilation system with the heat exchanger does an excellent job re-circulating the heat as I can see from the numbers on the controller. The biggest problem area is I think is our open living with kitchen area and that is 13.5m long and 5m wide and it connects to a large L shape hallway that leads to the office, media room, bedrooms etc. The hallway has 3 extractors. At start of hallway is an extractor duct for aircon, in the middle there is an extractor for the ventilation system and at end of hallway is the second extractor duct for aircon.

There are 2 wall controllers with the open living one set as master and master bedroom controller set as sub and the temperature readings and adjustment of aircon is set using the probe built into the wall controller that is set as master. I will try and switch master bedroom controller to master and that way a lot of heat will not be wasted/extracted by the ducts in hallway. I have to leave the ventilation system on also likely wastes a bit of heat generated in the house due to otherwise crying windows when it's cold. House is 2 years old double glazed. Unfortunately, we wanted thermal joinery but there was a mix up between the joiner and builder regarding time frames etc so we ended up with double glazing only with argon gas and green tints. We turn off the ventilation system in summer to not waste the aircon cooled air to outside. We also must leave the heating on in winter due to baby and toddler who get out of their blankets moving around too much in their sleep and they have a cold in morning otherwise.

I have set a timer on the aircon for past couple of weeks when temperature is around 10 to 12 degrees throughout the night to turn ON aircon for 30 minutes then turn it off and turn back ON again after an hour and repeat. This did reduce the energy use overnight quite a lot but it will not work next year when we are back in peak of winter. Same issue applies in summer. The aircon runs 24x7 with cooling.

Do whatever you want to do man.

billgates

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#2972999 26-Sep-2022 13:02

Mark:

Swap your induction hob for a gas one and you'll drastically bring down your power bill :-) Plus it wouldn't be fun trying to do an inverter setup to run it.

Are you sure you can be bothered selling back to the grid ? You'll only get a buy rate of $0.06, which is really not worth bothering about to me.

My house is a high power use house (family of 5 with kids who leave lights on all over, heat pumps, me in IT with too many computers about and an EV on a 15amp plug), in the past month we've used 1300kWh. Only 61kwH of which was from the solar and we've only exported 24kWh back to the grid.

System is 3kW of panels, 10kW of battery from Vector. When full and off grid it can power the house essentials (water pump, lights, internet, selected sockets and fridges/freezers for a day, and in summer could probably keep up without the grid)

Past 12months we have exported a grand total of 602kWh for a profit of $36 .. yay.

You might be better looking at investing in a good battery bank and then sizing the panels to keep it fed.

Induction cooktop is the best thing ever. Cleaning is so easy with less mess; kids are safe around it and it does not produce rising heat around the hob which your face feels like gas hob we had in past home. Genesis will give us 12c/kWh to sell back to grid and we get a lot of sun with house facing NW primarily. I am confident that we will produce a lot of energy from the panels.

Do whatever you want to do man.

billgates

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#2973061 26-Sep-2022 14:10

Thanks @eonsim for the PVoutput links. That has helped a lot getting info for summer and winter months and what others are getting with their setup and it even shows which model inverter and panels they use. The 1st link 'Maori Boy' seems to be exporting 100% of their generation back to the grid weirdly with none being used within their home. I can tell from their inverter model that they have a 3 phase setup. I checked our power meter and it is a 3 phase meter model however the main circuit switch is only 2 phase and the only other circuit in the panel that I can tell using the 2nd phase is the induction hob. This would just mean that I won't get the little bit of solar benefit for second phase for the induction hob as it will pull the power for from grid. I wonder in a blackout or power outage scenario, if the solar setup with battery can power some of the hobs on induction cooktop atll or there will be no power all to induction hob as it needs power from both phases to power ON? I will go with multiple inverters with an Island/Batery inverter + 15kW storage battery but keep them on same phase (phase 1) as that's where bulk of the usage is.

Do whatever you want to do man.

eonsim

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#2973069 26-Sep-2022 15:25

On PVoutput people only share what they want to, Maori Solar just isn't sharing there consumption, and the data for others is potentially only partially correct. Note it's not hard for an electrician to rearrange the circuits across multiple phases. But most likely having most of the house on the primary phase along with the inverters and batteries is the better option. No idea of the induction element needs 2 phases at once, or just one phase...

compound

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#2973118 26-Sep-2022 15:33

1st link is me. The 100% export is because I could not work out how to send data from 3 phases to PV Output. Has to be done manually and that is just too boring to do. Happy to discuss if you need to know some pitfalls and such.

billgates

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#2973135 26-Sep-2022 15:58

Awesome @compound. Your 11kW setup looks great and generations looks very healthy along with @eonsim 5kW system as well.

Are you happy with the Jinko Cheetah panels and Goodwe inverter? Do you have a battery storage system as well connected? If you don’t mind me asking, how much was your system as I am looking at around 10kW system.

@eonsim one of the 4 installers coming to provide a quote for solar this week hopefully is our electrician who cabled our home build 2 years ago. He will remember the full details of the 2 phase setup and will be able to confirm whether he actually ran 3 phase cable from street to home or only 2 phase. I do see 3 red cables and 1 white cable going into the meter which tells me 3 phase and 1 neutral possibly but of course meter only has 2 phases LED’s lit. Potentially I could look at 3 phase inverter which would save me $ from buying multiple single phase inverter.

Do whatever you want to do man.

billgates

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#2973145 26-Sep-2022 16:16

@eonsim we have good roof coverage for early to late morning as well. I took these photos standing in front of the respective roof areas. We have 2 long and straight roof location to host both NW and SE panels.

One run of NW roof is 23m long and other is 13.5m long. One run of SE roof is 23m long and other is 13.5m long. The 1st below is 23m long location I am thinking of putting the NW panels and 2nd photo is 13.5m SE panel location. Other side of both roof locations is of course opposite SE and NW respectively. There are no trees around us. Neighbour's have no trees. Yay covenants and our roof pitch is higher than both Neighbour's to our side hence why I am confident about plenty of sun for the panels.

Do whatever you want to do man.

eonsim

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Ultimate Geek

#2973278 26-Sep-2022 21:45

Looking at the numbers I don't think you'll realistically be able to get down to $50 a month. Assuming that usage was an average day year-round, and we assume an average daily generation of 35kWh (around a 9-10kW array) then adding solar and exporting everything saves you around 30% per year on your current Genesis plan, if you were to switch to Electric Kiwi or Octopus you would save ~54%.

If you had near-optimal use of your solar with a 15kWh battery (with 14% reserved), then sticking with your current genesis plan would save you approximately 44%. If you switched to EC/Octo then the savings would be approximately 66%. Note this is only at today's prices, if we expect electricity to get more expensive in the future then the savings will increase.

To get down to a zero energy bill you would need to have something like 20kW of panels. Possibly 15-16kWh with optimal use might get you close to the $50 a month if you changed to Electric Kiwi or Octopus. But at that level we are getting into very large systems, different rules, or the likelihood that you wouldn't be able to export all your excess generation due to the 10kW limit. So I'm really not certain about the modelling at that level of solar installation.

You can see the workings here, there are a number of assumptions so this is very much a rough estimate and is assuming the data you shared above is approximately an average day. Have a play, but remember it's a crude estimate.

https://docs.google.com/spreadsheets/d/19lpZgOGd1guuUkFXebhsGgy5TMY4gqULBMUoXzBWqJQ/edit?usp=sharing

eonsim

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#2973284 26-Sep-2022 21:51

billgates:

@eonsim one of the 4 installers coming to provide a quote for solar this week hopefully is our electrician who cabled our home build 2 years ago. He will remember the full details of the 2 phase setup and will be able to confirm whether he actually ran 3 phase cable from street to home or only 2 phase. I do see 3 red cables and 1 white cable going into the meter which tells me 3 phase and 1 neutral possibly but of course meter only has 2 phases LED’s lit. Potentially I could look at 3 phase inverter which would save me $ from buying multiple single phase inverter.

Note that if you use a three-phase inverter they mostly only do balanced output. As in if your generating 9kW, that will be split to 3kW per phase. So if one of the phases is using 9kW the three-phase inverter will only cover 3kW of that and you'll be buying the extra 6kW from the grid, at the same time your other two phases are exporting 6kW which means on the genesis tariff the 6kW will cost you $1.44 while you'll be earning $0.72 for your export and thus you'll be spending $0.72 to keep the house running while your technically generating enough power to cover your full usage.

Apparently, some 3-phase inverters can do unbalanced export, which would allow one phase to use more of the solar than the other two, but I'm not sure if that's 100% extra or more like and extra 30%.

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