Solar upgrade Southwest Sydney - Batteries, Micro inverters

I have 18 x 250 watt solar panels facing equally East and West on my house roof. Supposed to generate 4.5kW. Inverter is rated to 4kW. My retailer’s feed in tariff rates have just reduced this month from 9.5 cents to 0.07 cents per kWh. This was after a reduction from 0.10 cents in September 2020.

I’ve just been quoted $13,400 for the following system, which includes installation, from Skylight Energy of Rockdale.
Install 16 x 400 watt Hyundai PERC Shingle panels, 6 facing North, 3 West, 3 East & 4 flat on Western side carport which get Sun most of day and an LG Chem battery (not yet sure if RESU 6.5 or RESU 10). This brings the entire system up to 6.3KW. Inverter hopefully will be a 5KW Goodwe, as original quote was for a 5KW Huawei, but I’ve read a few bad reviews about these, although generally replaced under Warranty, and they’re Chinese, enough said in this current climate.
I was promised a reduction in my bills to almost nothing with the battery installed, but realistically, I’m hoping to reduce my quarterly bills to an average of $300 from $750.
Adding up my current quarterly bills from April 2020 to April 2021, the details are: General Usage: 11,198 kWh. Off Peak: 2,106 kWh. Feed-in: 2,189 kWh. Annual payment was $3,036.00 after a 25% discount off the total charge and the credit of $207.19 in feed in tariff.
As you can see by this, the electricity provider appears to be ripping me off with solar feed-in rates, so I need to consider a battery, with sufficient panels installed to re-charge it. I am based in Western Sydney with most of my roof facing East-West and some sections (with multiple valleys) facing North.
I get full Sun in Summer, about 6 hours Sun half-way through Spring and Autumn and about 5 hours sun in Winter. This is due to a neighbours large gum tree in my North-West corner blocking the sun during Winter for around 3 hours.


  1. Does this system size seem feasible in delivering the savings claimed?
  2. Is the price reasonable for this system?
  3. There are many mixed reviews about Skylight energy, mainly to do with after-sales service. Any issues known about this company?

G’day @Keith2, welcome back.

Our Solar & Battery Simulator should be able to help you with the first two questions.

Let me fire a couple back at you though.

  1. Why do you want to replace your current system?
  2. What’s your main reasoning for wanting your new system? Is it purely financial, or are there other reasons?


Thank you for responding so quickly. You can read the following diatribe, or just read my final sentence below.

To answer your questions below:

  1. My 18 x 250 Watt solar panels were installed 7 years ago. The output in Summer is around 25kWh per day, but Winter is in single figures.
    Those figures haven’t changed much since the panelsy were installed.
    The inverter, a SolarMax 4000P (4000 Watts) inverter, is no longer made and shuts down on a hot, clear, sunny day when input from the panels exceeds 4000 watts. Not sure if it’s the inverter, the grid or the heat which causes this.
    I have had the voltage supply checked over a week by Endeavour Energy and it is within their acceptable limits. I think that was from 230 to 254 volts.

  2. AGL Energy has just reduced my feed-in tariff to 7 cents per kWh. There is another AGL Plan which may allow me to claim up to 17 cents per kWh, but not sure yet if I’m eligible.
    Based on my last year’s bills (from April 2020 to now), and with a rebate of $0.07 cents per kWh, this means we will get less than $200 in cash rebates from our feed-in tariff annually!
    My electricity bill totals over $3,000 annually.
    Skylight Energy rep says the new system could save around $2,200 with just the panels and much more with the LG Chem battery.
    Based on their estimated minimum annual saving of $2,200, my bills should not exceed $200 per quarter and I get to pay off the new panels, inverter and battery in 6.3 years.

Basically, the plan is to install 16 x 400 Watt Hyundai panels; facing North (6), West (5) and East (5), with a separate inverter feeding to a LG Chem RESU 6.5 Battery.
Once battery is charged, the Hyundai panels feed in to the grid.
I have three-phase power.
The existing panels stay and just provide a feed-in to the grid only, as they do now. There was a significant cost to remove and/or replace the old panels.

I’m still not sure how they connect this feed-in to my meter so both sets of panels provide feed-in power to the grid simultaneously, but limited to 5kW per phase.

I am fed up paying around $750 per quarter (on average) for power and (I’ve been advised that) my existing panels will not be sufficient to re-charge a battery by themselves.

Keith C. Range

Ah, apologies, I misunderstood and thought your were removing the old panels. Makes sense what you’re saying.

I’m sceptical about this claim. I think you should ask for their calculations on this. Our calculations estimate you’ll save approximately $1600 just with solar. I think that’s more like “maximum” rather than “minimum”. If you ask for their calculations and they produce solid and transparent figures, it’ll help to find out what sort of company they are as well.

If you’re keen on getting a battery I think you should. There are more reason to get a battery than just financial. But I think it’s worth being clear on the financial equation so you can weigh it up. According to our calculations, 6.5kWh LG Chem battery adds about $5-7k to the cost of your system, and it will increase your annual savings by about $500. However, you might increase those savings if you explore a “Virtual Power Plant” (VPP) offering from AGL, or another provider. Basically this just means that your retailer can tap into your battery when the grid needs it most, and pay you a premium for that control. They tap your energy when electricity wholesale rates are through the roof, so it’s well worth them paying you a little more for it. Worth exploring.

Back to your original question, I don’t have any info that isn’t public on Skylight Energy. I would just suggest what we always do, to do your due diligence, and it’s probably worth getting a couple of other quotes to compare.

Hope that helps.

Thank you for that advice. I hope you are sitting down with a cuppa coffee before you read this?
I’ve put Skylight’s saleperson off until Monday, so I have time to think about this.
I’ll ask them for the “solid and transparent figures” as you suggest.
Now, you can skip the rest if you wish, or just go straight to my last sentence. But, please check the attachment.

They’re probably getting a bit sick of me asking so many questions and now I will bring up new ones such as how did they calculate the $2200 saving.

An inverter question I hadn’t known about until today.
I had requested a Goodwe 5kW inverter after Skylight’s salesperson had originally quoted a 5kW Huawei. I don’t wish to have Chinese products installed at this time, thank you very much.
I’ve just found out the Goodwe product is a “string” inverter.
Evidently, there’s a “Micro inverter” available that works more efficiently with the panels, especially half-cell panels, during cloudy days and when roof is partially shaded. However, I think these micro-inverters are way more expensive?
I would appreciate your opinion on the efficiency of the Goodwe “String” inverter. I’ve heard good reviews about the Goodwe product, but no-one has apparently discussed the shade question with these.

Half of my roof under these new solar panels will be in light-to-medium shade (due to a large (60’+) gum tree in neighbours yard in my North-Western corner) for around 3 hours per day, in late Autumn through to mid-spring. Full sun all day in Summer.
Just to give you some idea, I’ve attached an aerial photo of my place with the proposed 16 new panels in place and the 18 older ones shown in a lighter grey. The older panels are also smaller in physical size.
By what was parked in my front yard, the photo was taken on 6 March this year. You can see the shadow from the gum tree diagonally across my backyard. This shadow covers the back half of my roof for around 3 hours a day in mid-Winter.
The photo is a bit skewed as it’s slightly angled North-East. My block is almost due North/South.

I again thank you for your advice in this. There’s a lot (probably too much for me) to fully comprehend whether I’m getting a good equipment deal or not.
The old panels and inverter installed 7 years ago were a complete WOFTAM. I just don’t wish this to be another flop.

Anyway, if you have an opinion or experience with the Goodwe inverter and the part shade I have at my place, I would appreciate this.

Keith C. Range
Sydney NSW

(Attachment 20210427-Aerial photo of new panel placement.docx is missing)

Hi Keith

GoodWe is a Chinese brand too, just less known than Huawei.

The only real micro inverter option is Enphase, but you have a similar panel level optimiser in SolarEdge, and Tigo. It’s your turn for a big read now!:

Unfortunately it’s not clear cut, and really dependent on your specific situation. You’ll need to find someone that really knows their stuff, and can do a proper assessment for your needs. I don’t have any hot tips for great installers I’m afraid, you might just need to sift through a few on Google.

Hope that helps.


Interesting reads. I was told some time ago that Goodwe were a European brand, but I’ll take your word for it that they’re Chinese. Might ask Skylight about the price for a Fronius inverter.
After reading all the attachments, I don’t think a Micro inverter is needed in my situation (including the additional cost) as I will only get shade on around a third of my panels (5 out of 16) at any one time and only for a few hours in mid-Winter,
however, I’ll also ask Skylight about the “Solar Edge” and “Tigo” power inverter options.
Skylight were also installing “Optimisers” on those panels that will be subject to some shading. I had no clue what these were until after I “talked” to you and read the stuff below. Thank you.
Hopefully, I’ve absorbed a bit of what you have sent me.
Now to ask Skylight some questions when they call me on Monday.

Thanks again & regards,
Keith C. Range

Hi Keith,
Great to see someone that explains matters in such detail.

People need to start treating Retailers like Phone providers, simply change to the ones offering a better rates, as the Rip-off Retailers Don’t actually supply anything other than a Bill.

As you already have 3 phase power, you are legally be able to Export 30kW per hour, that is Great if you actually had a large Solar array.

We deal with over 95% of people that live Off-Grid, and this is what I suggest to do;

  1. Purchase either Goodwe or Huawei 5kWh Hybrid battery inverter $2’600.00, they are both Great inverters, however with 3phase you should be able to install a Huawei 30kWh inverter for $3’600.00, but I suspect that is way to big for your amount of Excess energy Generation.
  2. Purchase 2x 10.24kWh LiFePO4 Batteries (=20.48kWh), current cost is $8’550.00, 3x 10.24kWh batteries =$12’075.00 very affordable @$395 per kWh.

Keith: Martin is right, you Why are you putting in More Generation !
As you are already Exporting Energy, the Smart thing you could do, is Charge your Batteries with Just the 9kWh Day you are currently gifting back to the Grid @7c kWh, that just Pays for the Charges to Remain Grid connected.
So, simply Charge your Batteries First, and Only when batteries are fully charged, would you be Gifting your Excess Energy for the Feed-in Rate, see the Retailer Con statement Below, do the numbers!

With a clear head, we suggest people see if it is worth remaining connected to the State Grid !
As most people don’t do the maths on why they don’t actually Save what many Solar Retailers say, as it’s partly due to the underlying costs to remain Grid connected !

We strongly believe people who Generate/Feed Energy into the State Grid, should NOT be Charged a Fee to be/remain connected, just like commercial Solar Farms, as State & Private Generators are both doing the same thing, providing a Product through the Distributors lines.

The Big Retailer CON: People Exporting there Solar Energy into the State Grid at 10c kWh, have to Gift the first 800kWh of energy to just pay for an $80 “Service Charge”, just to remain connected to the State-Grid.

What many people are Not aware of, Your Solar energy is going to your Neighbours down the line, where the “Rip-off Retailers” Charge some 30c kWh for your energy, thus Profiting a further $240 for the same 800kWh energy you have already gifted them, totalling some $320, and don’t forget any remaining unused energy you export provides the Retailers with even more profit!

The State Grid can easily be Replaced by a $900, 3.5kw Fuel Generator, all generators should have a Starter motor if you require a totally automated system, that will only start for a few hours, commonly after long periods of Bad weather, as that is what nearly all Off-Griders live with.

For the above reasons, it’s now Smarter to Invest in More Energy Storage than Solar, the tables have turned on Energy Storage !

Not many people can afford Super Capacitor Energy Storage Modules, however these are currently the Latest & Greatest Energy Storage Technology, the cost is currently $900 per kWh, and claim to have a 50’000 cycle life.

Good Luck with your project.

For the record, I am a strong advocate for the grid. I think the world would be a far worse place (and electricity enormously more expensive, both in dollars and carbon) if everyone went off grid, needing a huge battery system or a stinky inefficient generator.

However, I agree with @TheRaptor’s point that it would be nice if the retail cost and price of electricity was more aligned with the wholesale cost/price. That would create a lot of efficiencies.

True that!

I wish we could go back to the time when Energy companies were statutory Government Authorities, supplied the poles, wires, pipelines, meter boxes AND sent out the bills. And the electricity/gas prices stayed the same for year on year and cheap with it.
Once privatised, all they care about is paying shareholder dividends FROM OUR MONEY.
Enough of my rant.


With all respects, I believe that statement is largely misleading !

Setting aside that the wholesale rate is from 6c~10c per kWh for businesses that consume upwards of $40’000 per month, but the final bills are stacked with grossly inflated costs including all the Carbon froth & bubble.

If everyone purchased there own Micro Power Grid, I believe the cost would be under $20k for 90% of Residential customers.

As for “stinky inefficient generators”, Diesel generators can actually be converted to operate on 70% natural Gas, but that is just semantics, as all modern generators will provide Power at 27c kWh with Fuel that costs $1.30 per litre.

Use this Generator Fuel Cost Calculator;
Although, if one had a supply of filtered/treated Bio-degradable Wast Vegetable Oil, there would be some 70% less Toxic Pollution.

Generators only become inefficient if all the Power is Not consumed or Stored during operation, e.g. Like a Tradesman operating a Generator on a site with No power, all the Power is Wasted if nothing is being used.

Go google Norfolk Island power, it screams of Bureaucratic incompatible, Massive Solar Generation, with old Expensive Diesel Generators operated after Sunset & apparently energy costs 75c per kWh until Sunrise.

We believe investing in Batteries will just become like purchase expensive White Goods or small vehicle.
We should all Hale, “long-term Energy Storage for the smart investors!”
Only my views. :nerd_face:

Me too! I think we’re on the same page, but I think the grid still plays a fundamental role.

The wholesale rate for electricity can be very low, it can also be eyewateringly high. Businesses also pay a supply charge based on their peak demand. This is what is expensive, whether for a residential off-grid system, or a commercial on-grid, it’s meeting the peak load that costs the big money.

I understand that the Bleeding rate for Peak Demand Energy has/can exceed some $1’800kWh or is it kW…
However, that is usually only for a Very short period, I am told, although the Adelaide Saga a few years back may have been part of the bleeding, so to speak.

People with the Authority, should be Mandating that every Main Power Station or Sub-station, where there is an Oversupply of Energy, should have some form of Energy Storage Technology Installed, we only know of three contenders in the Commercial Energy Storage Technology currently, one is an Australian 10MW TESS Module (Thermal Energy Storage System).

Well that may be dreaming to expect that those with the Authority in the Energy Department would have the Vision!, especially with all the current Talk about Charging/Taxing Customers for the Over Supply of Energy, the same Service the Distributors are also providing.

So, we wonder if we will ever have an Open Energy Market that implements Peer-2-Peer Energy Trading to all Generators.