Solar options for home in 2022.

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969 posts

Ultimate Geek

Subscriber

#3285388 23-Sep-2024 10:54

Chewbacca:

After reading all 48 pages of this thread and I am getting closer to actually getting a system

So ideal system for ROE is 5kw with lets say 7kw of panels (but also looking at larger systems). I can only export 5kw at a time, as i believe i only have a single phase (looking at the meter outside it says single phase, my switchboard isolator is two wide)

On some earlier post, someone indicated that the cost of a bigger inverter may only be a few hundred dollars. So why wouldn't i go for the same 7kw of panels on a say a 6.5 kw inverter. As in the middle of summer i am there will be periods i cant use all my power generation (via use or export), does this become an issue?

Be aware that the export cap only applies to the generation you are unable to consume at any given time so a 7kW system running at maximum output minus 2kW of 'background' consumption would see you matching the export cap with no throttling of the inverter required. A HWC diverter will fill this purpose for the first few hours of the day as will a battery if your financial modelling can make that work. Export should be your last choice so far as economic return goes. Self consumption is king as it offsets consumption that would otherwise cost you retail rates (including GST). Export rates are far short of this in most cases.

For the low extra expense involved in installing a larger inverter is worthwhile IMO as it may give you the opportunity to add a bit more panel capacity and if you add an EVSE which is typically 7kW requirement you are closer to being able to match that from solar alone, though an EVSE like the Evnex ones will limit their output to match solar 'excess' if your solar generation falls short of 7kW.

We have an 8.2kW single phase inverter with 9.5kW of panels and manage to keep our consumption at a level ~80+% of the time that prevents the inverter having to throttle back to satisfy our 5kW cap. We do work from home so can manage our system and consumption manually to a greater degree than most people I guess.

Also worth checking your lines company's T&Cs in regard to export as there are some that allow >5kW with The Lines Company in Waikato/King Country region allowing 6kW.

https://www.harmlesssolutions.co.nz/

Chewbacca

5 posts

Wannabe Geek

#3285396 23-Sep-2024 11:33

HarmLessSolutions:

Chewbacca:

After reading all 48 pages of this thread and I am getting closer to actually getting a system

So ideal system for ROE is 5kw with lets say 7kw of panels (but also looking at larger systems). I can only export 5kw at a time, as i believe i only have a single phase (looking at the meter outside it says single phase, my switchboard isolator is two wide)

On some earlier post, someone indicated that the cost of a bigger inverter may only be a few hundred dollars. So why wouldn't i go for the same 7kw of panels on a say a 6.5 kw inverter. As in the middle of summer i am there will be periods i cant use all my power generation (via use or export), does this become an issue?

Be aware that the export cap only applies to the generation you are unable to consume at any given time so a 7kW system running at maximum output minus 2kW of 'background' consumption would see you matching the export cap with no throttling of the inverter required. A HWC diverter will fill this purpose for the first few hours of the day as will a battery if your financial modelling can make that work. Export should be your last choice so far as economic return goes. Self consumption is king as it offsets consumption that would otherwise cost you retail rates (including GST). Export rates are far short of this in most cases.

For the low extra expense involved in installing a larger inverter is worthwhile IMO as it may give you the opportunity to add a bit more panel capacity and if you add an EVSE which is typically 7kW requirement you are closer to being able to match that from solar alone, though an EVSE like the Evnex ones will limit their output to match solar 'excess' if your solar generation falls short of 7kW.

We have an 8.2kW single phase inverter with 9.5kW of panels and manage to keep our consumption at a level ~80+% of the time that prevents the inverter having to throttle back to satisfy our 5kW cap. We do work from home so can manage our system and consumption manually to a greater degree than most people I guess.

Also worth checking your lines company's T&Cs in regard to export as there are some that allow >5kW with The Lines Company in Waikato/King Country region allowing 6kW.

Thanks thats what I thought. We are in Auckland so limited to the 5kw. Like the idea of the battery, but realistically this purchase is a bit of financial and a bit of feel good and the added cost of a battery at this stage turns a medium purchase into an expensive purchase which I can't really justify.

I had looked into a solar only system a few years back, and would probably been 1/2 through a 10 year payback period had i done it then. With my bank offering interest free seems a bit more like a no-brainer (on the basis i can afford higher repayments than my savings on power).

HarmLessSolutions

969 posts

Ultimate Geek

Subscriber

#3285443 23-Sep-2024 13:58

Chewbacca:

HarmLessSolutions:

Be aware that the export cap only applies to the generation you are unable to consume at any given time so a 7kW system running at maximum output minus 2kW of 'background' consumption would see you matching the export cap with no throttling of the inverter required. A HWC diverter will fill this purpose for the first few hours of the day as will a battery if your financial modelling can make that work. Export should be your last choice so far as economic return goes. Self consumption is king as it offsets consumption that would otherwise cost you retail rates (including GST). Export rates are far short of this in most cases.

For the low extra expense involved in installing a larger inverter is worthwhile IMO as it may give you the opportunity to add a bit more panel capacity and if you add an EVSE which is typically 7kW requirement you are closer to being able to match that from solar alone, though an EVSE like the Evnex ones will limit their output to match solar 'excess' if your solar generation falls short of 7kW.

We have an 8.2kW single phase inverter with 9.5kW of panels and manage to keep our consumption at a level ~80+% of the time that prevents the inverter having to throttle back to satisfy our 5kW cap. We do work from home so can manage our system and consumption manually to a greater degree than most people I guess.

Also worth checking your lines company's T&Cs in regard to export as there are some that allow >5kW with The Lines Company in Waikato/King Country region allowing 6kW.

Thanks thats what I thought. We are in Auckland so limited to the 5kw. Like the idea of the battery, but realistically this purchase is a bit of financial and a bit of feel good and the added cost of a battery at this stage turns a medium purchase into an expensive purchase which I can't really justify.

I had looked into a solar only system a few years back, and would probably been 1/2 through a 10 year payback period had i done it then. With my bank offering interest free seems a bit more like a no-brainer (on the basis i can afford higher repayments than my savings on power).

If you're not going down the battery direction then I strongly recommend adding a diverter to your installation. Our Paladin (NZ made) is the single best ROE item in our system. It allows your HWC to serve as a de facto battery storing excess generation as heat and pretty much cancelling out any hot water heating from the grid. In our case it typically soaks up all the spare generation until about 11:00am after which we put the EV charging into play, all to avoid hitting the export cap.

https://www.harmlesssolutions.co.nz/

mentalinc

3226 posts

Uber Geek

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#3285789 24-Sep-2024 12:54

@chimera how are you finding the system now you've had it for a few weeks, and do you have any finished photos?

CPU: AMD 5900x | RAM: GSKILL Trident Z Neo RGB F4-3600C16D-32GTZNC-32-GB | MB: Asus X570-E | GFX: EVGA FTW3 Ultra RTX 3080Ti| Monitor: LG 27GL850-B 2560x1440

Quic: https://account.quic.nz/refer/473833 R473833EQKIBX

neb

11294 posts

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Lifetime subscriber

#3286896 27-Sep-2024 00:07

Partially borrowing this solar thread to avoid starting yet another one: Friend of mine is using a HWC with 48V element run from a MPPT controller with solar cells he got cheap as a preheater for his main HWC. So the idea is to heat the 48V-solar cylinder during the day, then run it into the main HWC when it's needed, using the water as energy storage.

Does anyone have any thoughts on this? Sounds like an interesting idea, although possibly one involving a bit of effort to move the solar-heated water into the main HWC, for which I'm unclear on the details ATM.

fastbike

212 posts

Master Geek

#3286902 27-Sep-2024 06:19

neb:

Does anyone have any thoughts on this? Sounds like an interesting idea, although possibly one involving a bit of effort to move the solar-heated water into the main HWC, for which I'm unclear on the details ATM.

Sounds like there are going to be situations where you have hot water in the secondary cylinder and cold water in the primary. How are you going to avoid it mixing ?We considered a similar setup 20 years ago when building, only in our case there would be a solar thermal pre heat tank on the roof which would feed an electric cylinder. We went with a slightly larger HWC with two independent elements (1/3 from top, 1/3 from bottom) and the solar thermal loop at the base.

For your case, why not connect the solar PV panels directly to the cylinder with a double channel contactor (configured NO / NC) and some control electronics ... one contactor channel for AC and one for DC. When the sun is shining the contactor will connect the PV to the element. And during cloudy/night it will be connected to the normal AC with what ever controls (timer / ripple etc) exist. Some type of hysteresis to prevent it hunting when the sun is weak, and a manual over ride switch. Apart from wiring the contactor all other is safety low voltage.

Edited to add additional info.

Otautahi Christchurch

neb

11294 posts

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#3287012 27-Sep-2024 14:11

I don't know all the details but I think a lot of it was based on the fact that they got the panels and a cylinder cheap (and I mean really cheap, $130 for 430W panels) and did what they could with what was at hand.

timbosan

2159 posts

Uber Geek

#3290144 2-Oct-2024 17:21

Hey all,

So, my turn on the solar bandwagon :-) I have been looking at solar for a while and have just had Harrisons give an updated quote. 5kw system split 6 panels north + 5 panels east, 5kw Fronius inverter.

* Currently on a 2 year fixed with Mercury and only pay 14c / kWh flat rate. But that does end in March.
* Looking at moving to PowerEdge for the supplier with their 20c (GST incl.) buyback
* Not looking at a battery
* 2 people home all the time.
* Heat Pump hot water to be installed in 2 weeks (replacing very old system that is starting to have issues)
* No current plan on timer or diverter
* 40Kw Nissan leaf with existing Charge Amps charger, 90% of the time charged at home
* Genless says 10 year payback

I have been running the numbers on sites such as genless, but I am having issues trying to nail down actual viability based on my usage. Is there a way to figure this out? I can time shift a lot of usage due to being home all the time but how do I estimate what I could save of if its better to stay on my current plan?

I am open to suggestions, and have read a lot on CT clamps and pushing excess power into water heating or the EV, etc.

HarmLessSolutions

969 posts

Ultimate Geek

Subscriber

#3290148 2-Oct-2024 17:34

timbosan:

.......
I have been running the numbers on sites such as genless, but I am having issues trying to nail down actual viability based on my usage. Is there a way to figure this out? I can time shift a lot of usage due to being home all the time but how do I estimate what I could save of if its better to stay on my current plan?

I am open to suggestions, and have read a lot on CT clamps and pushing excess power into water heating or the EV, etc.

Tying down the earnings from a PV set-up is difficult though once you've got up and running a software package such as Solar Analytics does a good job of this with facility to input different plans and/or TOU rates.

From our experience any device that modulates its consumption of 'excess' generation by way of a CT clamp is definitely the way to optimise your system's viability. We run 3x CT clamps, for the inverter's 5kW export cap, a Paladin HWC diverter and an Evnex EVSE. The Paladin in particular is the single best investment in our solar system. This HWC diverter is super reactive and ensures that consumption very closely matches our generation (up to 3kW) until the HWC maximum temp is reached which typically is 10:30-11:30am each day.

https://www.harmlesssolutions.co.nz/

timbosan

2159 posts

Uber Geek

#3290149 2-Oct-2024 17:38

HarmLessSolutions:

timbosan:

.......
I have been running the numbers on sites such as genless, but I am having issues trying to nail down actual viability based on my usage. Is there a way to figure this out? I can time shift a lot of usage due to being home all the time but how do I estimate what I could save of if its better to stay on my current plan?

I am open to suggestions, and have read a lot on CT clamps and pushing excess power into water heating or the EV, etc.

Tying down the earnings from a PV set-up is difficult though once you've got up and running a software package such as Solar Analytics does a good job of this with facility to input different plans and/or TOU rates.

From our experience any device that modulates its consumption of 'excess' generation by way of a CT clamp is definitely the way to optimise your system's viability. We run 3x CT clamps, for the inverter's 5kW export cap, a Paladin HWC diverter and an Evnex EVSE. The Paladin in particular is the single best investment in our solar system. This HWC diverter is super reactive and ensures that consumption very closely matches our generation (up to 3kW) until the HWC maximum temp is reached which typically is 10:30-11:30am each day.

Thanks :-) I think I have read your previous posts on the Paladin - but would it be worth it with a heat-pump hot water cylinder vs. a timer?

I did ask Harrisons about this (Nerum for those who know Harrisons, I have always found him easy to deal with) and he mentioned that an EV would be just another 'appliance', how would the Evnex differ? Does it push ALL solar (above the base rate) into EV rather than just "powering the house"?

HarmLessSolutions

969 posts

Ultimate Geek

Subscriber

#3290155 2-Oct-2024 18:00

timbosan:

Thanks :-) I think I have read your previous posts on the Paladin - but would it be worth it with a heat-pump hot water cylinder vs. a timer?

I did ask Harrisons about this (Nerum for those who know Harrisons, I have always found him easy to deal with) and he mentioned that an EV would be just another 'appliance', how would the Evnex differ? Does it push ALL solar (above the base rate) into EV rather than just "powering the house"?

I'm not familiar with HP HWCs but for a conventional HWC a diverter will 'mop up' all generation that would otherwise be exported (up to the rating of the HWC element) and in doing so perfectly matches your consumption to your generation. As I understand that HP efficiency will top that of a resistance element the gain won't be as marked in your case for a diverter I guess.

In terms of priorities any household demand takes precedence and if there is 'excess' generation over and above that the Paladin draws up to the generation level. An Evnex works in the same way as the Paladin but with a ~1.4kW threshold which is typically the lowest rate an EV will accept charge at. The Paladin is more instantaneous than the Evnex so gains priority over EV charging due to that by being quicker to activate.

We also have an older EVSE which we use for the Leaf (we have our reasons) but this pulls ~3.3kW regardless of the generation occurring, so on an overcast or intermittent cloud day it will often draw enough from the grid to reach its charging capacity. For this reason Leaf charging is usually done in sunny conditions or else scheduled to night rates for us so we avoid 'topping up' partially from shoulder or peak rates. The all or nothing issue with this EVSE puts it on an equal (high) priority as any other house demand from appliances.

https://www.harmlesssolutions.co.nz/

LightbulbNeil

57 posts

Master Geek

#3290157 2-Oct-2024 18:02

I was talking with someone today about solar and heatpump hotwater. Also connecting the car. He's looking st some system that the house is 1st, then the heatpump hotwater with the extra sun. The car is connected to the heatpump hotwater to it works seamlessly making hot water. The clouds come and the car is the battery. Extra sun and the car charges. No idea how it works exactly. His car is a BYD Atto3. No idea how its going to work in winter though. They are in the Wellington region. They are looking at a 25kw system . So assuming its 3phase. They don't have to use the car and can get to work on trains etc.

timbosan

2159 posts

Uber Geek

#3290158 2-Oct-2024 18:06

LightbulbNeil: I was talking with someone today about solar and heatpump hotwater. Also connecting the car. He's looking st some system that the house is 1st, then the heatpump hotwater with the extra sun. The car is connected to the heatpump hotwater to it works seamlessly making hot water. The clouds come and the car is the battery. Extra sun and the car charges. No idea how it works exactly. His car is a BYD Atto3. No idea how its going to work in winter though. They are in the Wellington region. They are looking at a 25kw system . So assuming its 3phase. They don't have to use the car and can get to work on trains etc.

Some EV's offer V2G / V2H (the Leaf was supposed to offer this but AFAIK only offers it in Japan, and wasn't a reason I brought it).

There are some 'hacks' that attach an external inverter to a Leaf and you can plug in appliances, but there are cabling challenges if you park outside like I do :-) for example https://www.reddit.com/r/leaf/comments/16vrixx/v2l_from_leaf/

Jase2985

13457 posts

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Lifetime subscriber

#3290195 2-Oct-2024 19:19

timbosan:

Hey all,

So, my turn on the solar bandwagon :-) I have been looking at solar for a while and have just had Harrisons give an updated quote. 5kw system split 6 panels north + 5 panels east, 5kw Fronius inverter.

* Currently on a 2 year fixed with Mercury and only pay 14c / kWh flat rate. But that does end in March.
* Looking at moving to PowerEdge for the supplier with their 20c (GST incl.) buyback
* Not looking at a battery
* 2 people home all the time.
* Heat Pump hot water to be installed in 2 weeks (replacing very old system that is starting to have issues)
* No current plan on timer or diverter
* 40Kw Nissan leaf with existing Charge Amps charger, 90% of the time charged at home
* Genless says 10 year payback

I have been running the numbers on sites such as genless, but I am having issues trying to nail down actual viability based on my usage. Is there a way to figure this out? I can time shift a lot of usage due to being home all the time but how do I estimate what I could save of if its better to stay on my current plan?

I am open to suggestions, and have read a lot on CT clamps and pushing excess power into water heating or the EV, etc.

given you appear to be home all the time and have most things electric, i cant see you selling to much back to the grid unless you shift most of your daytime use to the night

The problem with a heat pump HWC and solar is they dont like cycling on and off due to their being no power being generated and require a minimum of 6-800kw to run, unlike a regular hot water cylinder which will run on much less using a diverter. So this would likley need to be on just a timer, and it will run if there is solar or not.

What are the power rates day and night with them like? this will likely dictate if its worth it or not.

Do you have your current half-hourly usage? You could throw that into a spreadsheet and do some calculations based on the different providers. For us, even though we could have gotten 17c buyback on meridians plan, but their day/night rates were more, and overall ended up being more expensive than the plan we went with.

timbosan

2159 posts

Uber Geek

#3290203 2-Oct-2024 19:42

Jase2985:

timbosan:

Hey all,

So, my turn on the solar bandwagon :-) I have been looking at solar for a while and have just had Harrisons give an updated quote. 5kw system split 6 panels north + 5 panels east, 5kw Fronius inverter.

* Currently on a 2 year fixed with Mercury and only pay 14c / kWh flat rate. But that does end in March.
* Looking at moving to PowerEdge for the supplier with their 20c (GST incl.) buyback
* Not looking at a battery
* 2 people home all the time.
* Heat Pump hot water to be installed in 2 weeks (replacing very old system that is starting to have issues)
* No current plan on timer or diverter
* 40Kw Nissan leaf with existing Charge Amps charger, 90% of the time charged at home
* Genless says 10 year payback

I have been running the numbers on sites such as genless, but I am having issues trying to nail down actual viability based on my usage. Is there a way to figure this out? I can time shift a lot of usage due to being home all the time but how do I estimate what I could save of if its better to stay on my current plan?

I am open to suggestions, and have read a lot on CT clamps and pushing excess power into water heating or the EV, etc.

given you appear to be home all the time and have most things electric, i cant see you selling to much back to the grid unless you shift most of your daytime use to the night

The problem with a heat pump HWC and solar is they dont like cycling on and off due to their being no power being generated and require a minimum of 6-800kw to run, unlike a regular hot water cylinder which will run on much less using a diverter. So this would likley need to be on just a timer, and it will run if there is solar or not.

What are the power rates day and night with them like? this will likely dictate if its worth it or not.

Do you have your current half-hourly usage? You could throw that into a spreadsheet and do some calculations based on the different providers. For us, even though we could have gotten 17c buyback on meridians plan, but their day/night rates were more, and overall ended up being more expensive than the plan we went with.

That's actually a really good point re the heat pump hot water, originally I thought of a timer, so will get a quote from the sparky for that.

PowerEdge, on their Power Shield plan (fixed for 5 years) are:

Fixed daily fee: 196c per day (fixed for 5 years)
Night Import rate: 20.3c per kWh (fixed for 5 years)
Day Import rate: 23.3c per kWh (fixed for 5 years)
Export rate: 17.39c per kWh (20c incl GST) (fixed for 5 years)
Electricity Authority Levy: $0.0015 per import kWh

I thought the above were pretty good, especially the higher buy-back. For reference my current plan on Mercury is 14.8c flat and 8c buyback.

Do you have your current half-hourly usage? Yes I can export this, good idea!!!!

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