Is my Solar quote decent?

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cruxis

482 posts

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#316279 1-Oct-2024 21:16

A 2024 New build H1 house. I asked for best coverage for North and East facing with hot water diverter, Also inverter must work with home assistant is a No 1 priority. Does anyone know for sure? Does it matter the inverter is oversized ?

Also should I just drop those 3 east panels next to the gulley and go down to 7.5kwh and a 5kWh inverter undersized instead.

Current House daily usage is 30kWh winter, 21kWh summer

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BDFL - Memuneh
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Geekzone

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#3288867 1-Oct-2024 23:53

It was really hard to read, so I removed the size attributes from the images.

cyril7

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#3288873 2-Oct-2024 07:03

Hi, my only thought (putting on my electrical engineering hat) is its not normal engineering practice to undersize things, your just asking for them to go bang, hence a 10kW inverter with a potential 7-8.5kW of throughput is probably the only sensible solution.

Cyril

Ge0rge

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#3288882 2-Oct-2024 08:21

cyril7:

Hi, my only thought (putting on my electrical engineering hat) is its not normal engineering practice to undersize things, your just asking for them to go bang, hence a 10kW inverter with a potential 7-8.5kW of throughput is probably the only sensible solution.

Cyril

With solar inverters it is normal to oversize the panel output with respect to the inverter, and I haven't seen many that aren't technically rated for this. They will have a maximum input capacity, and a rated output - the former being higher than the later.

Jase2985

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#3288886 2-Oct-2024 08:30

cyril7:

Hi, my only thought (putting on my electrical engineering hat) is its not normal engineering practice to undersize things, your just asking for them to go bang, hence a 10kW inverter with a potential 7-8.5kW of throughput is probably the only sensible solution.

Cyril

doesn't generally apply with solar inverters, they are normally rated to 120-150% the normal capacity.

Bung

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#3289894 2-Oct-2024 09:36

W E

cyril7

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#3289895 2-Oct-2024 09:37

Roger, I guess it's how you interpret the quoted solution, if your expecting 8.5kW of potential supply, then I assume. 10kW inverter is appropriate, the fact that you have 15kW of panel potential on tap is not really relevant, except that there is sufficient to achieve the output, is that the correct way to consider it?

Cyril

wellygary

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#3289897 2-Oct-2024 09:41

if you are slapping them hard on a roof with a minimal gap , can someone tell me what benefit you gain from "bi-facial"modules??

or are they simply the most available and hence cheapest

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CYaBro

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#3289906 2-Oct-2024 10:05

wellygary:

if you are slapping them hard on a roof with a minimal gap , can someone tell me what benefit you gain from "bi-facial"modules??

or are they simply the most available and hence cheapest

Bifacial panels have clear gaps between the cells themselves and let some amount of light through to the mounting surface to reflect onto the back of the panels.

Opinions are my own and not the views of my employer.

Scott3

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#3289908 2-Oct-2024 10:14

Note I don't do residential solar, so some of my comments may be a little off.

On the inverter, Solar inverters are typically rated to be undersized and can accept a DC:AC ratio of somewhere between 1.5 & 2 depending on brand. Setting up with a DC:AC ratio of ~1.2 is often seen as optimal. Means a cheaper inverter, that is better utilized, but you do loose a little energy to clipping.

But this clipping loss is when solar generation is abundant anyway. And per $ of system, this will allow more power to be generated in adverse conditions (away from the center of the day, degraded panels after a few years, cloud cover).

What is Solar Inverter Clipping? | inverter.com

I can't find the data sheet for the selected inverter, but guess that they have picked the larger inverter because of the significant imbalance between string sizes. (typically the inverters are strictly equal capacity to each string).

Bung:

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This is the big one. OP has asked for their system to favor east (morning), but the layout favors west (afternoon evening). And the angle that the house sits favors utilizing that area above the front door.

Assume the company has a default to either avoid the street facing bit of roof for esthetic's, or to favor afternoon generation, when residential consumption is often higher.

richms

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#3289910 2-Oct-2024 10:25

cyril7:

Hi, my only thought (putting on my electrical engineering hat) is its not normal engineering practice to undersize things, your just asking for them to go bang, hence a 10kW inverter with a potential 7-8.5kW of throughput is probably the only sensible solution.

Cyril

You are limited on inverter size that you can connect, so if you are not doing export limiting with a CT on the mains, the only way to comply is to actually get an inverter sized for what you are allowed and then overpanel it so that you are at its limit for a decent chunk of the day for a sunny day, and get more useful output on less than ideal days when its cloudy or a season when its well off the best axis.

Richard rich.ms

richms

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#3289911 2-Oct-2024 10:27

wellygary:

if you are slapping them hard on a roof with a minimal gap , can someone tell me what benefit you gain from "bi-facial"modules??

or are they simply the most available and hence cheapest

They are all doing that now since its basically them not painting the back of the panel, its zero manufacturing cost to claim it, and they get to put a bigger wattage rating on the panel which it will never see in real life so more reason to go absurd with over paneling.

There is basically no limit to overpanelling if the string open circuit voltage is within range of the inverter, and most bifacial are the same voltage just higher current as they have the same cell count.

Richard rich.ms

fastbike

212 posts

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#3296844 13-Oct-2024 10:39

Just to jump in on this thread, I'm currently getting quotes for a solar installation. The house is a little tricky as it has a curved mono pitched roof, and is concrete block with a concrete intermediate floor. But otherwise it is a good site as it faces almost due north, the roof has a good pitch, has almost no shading, and panels can be installed as 3 or 4 rows (depending on whether landscape or portrait gives best mount fixings).

I've specified that I will install the HD PVC conduit (I have the kit required to core drill through the concrete). I'm also doing the supply and installation of the rails.

So the demarcation point is the rail - the installers are responsible for everything above the rail i.e. all wiring incl earthing, panel supply and installation, inverter, switch gear, inspection and certification.

We have room for 26 panels so for a std 440W panel this should give 11.4kW with a 10kW 3 phase inverter.

I've had two quotes come back in so far:

the first is one of the franchised nationwide sales outfits and has pretty much ignored my input and quoted for 26 Longi panels and a 10kW SolaX hybrid inverter and added a Green Catch hot water power diverter.
The cost for this is $30k, subject to agreement with the installer related to the rail installation, so likely higher.
The next is from a smaller family run business who will be doing the actual work themselves. They're happy for me to do the conduit and mounts. The have quoted on 26 TW panels and a 10kW Solis hybrid inverter. Interestingly this inverter has 4 separate MMPT inputs so there is more flexibility in how the panels are hooked up.
Their cost is $20k but is very light on exactly what is included, so I'd be expecting the final bill to be higher unless I get more detail on what is included/excluded.

Should I look around for another quote, e.g. a local electrician to see if I can add a bit more sweat equity by working with them to do the actual panel installation (I'm comfortable being on the roof as I helped build the house and have all the safety gear/roof harness etc). I can access the panels for around $200 incl GST, so I'm struggling to see where the balance of the quote comes from.

Otautahi Christchurch

RobDickinson

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#3296952 13-Oct-2024 14:40

$30k for 11kw panels and an inverter + green catch is $4k shy of what I paid for 9kw+ PW3 + green catch

Ak roof and 3 phase may make that a lot more spendy tho

I would def recommend more quotes and talk to a sparky about more diy

fastbike

212 posts

Master Geek

#3296957 13-Oct-2024 15:12

RobDickinson:

$30k for 11kw panels and an inverter + green catch is $4k shy of what I paid for 9kw+ PW3 + green catch

Ak roof and 3 phase may make that a lot more spendy tho

I would def recommend more quotes and talk to a sparky about more diy

Thanks for the intel. Do you know roughly what the PW3 (installed) would be out of your system cost ?

And yes, I think I need to just work with a sparky given the significant input I'm already making. If I supply the panels then I will buy a pallet (36) to get a better price and after the house is done and connected (there is a 10kW export limit) then either sell the panels or put the other 10 on the garage. There is some shading there so optimisers or micro inverters might be required, but that is a problem for next month, not this month LoL.

Otautahi Christchurch

dazdaz

21 posts

Geek

#3297058 13-Oct-2024 22:13

richms:
wellygary:

if you are slapping them hard on a roof with a minimal gap , can someone tell me what benefit you gain from "bi-facial"modules??

or are they simply the most available and hence cheapest

They are all doing that now since its basically them not painting the back of the panel, its zero manufacturing cost to claim it, and they get to put a bigger wattage rating on the panel which it will never see in real life so more reason to go absurd with over paneling.

There is basically no limit to overpanelling if the string open circuit voltage is within range of the inverter, and most bifacial are the same voltage just higher current as they have the same cell count.

Bifacial panels are not just mono panels unpainted on the bottom side. Bifacial have glass on two sides, mono do not. And generally they are rated to the wattage on a single side, any extra wattage gained from the back side is a bonus. There are plenty of comparisons on YouTube.

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