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STCs or the 'Rebate' as it is commonly, but incorrectly called. (It's not a rebate)

If you install 6.6kW of new panels in Perth, in 2020, you earn 100 STCs
The value of each STC is, at time of writing, trading at $37
So you get a discount of 100 x $37 = $3,700

There is a formula to work out how many STCs you are entitled to...
In 2020, you multiply 15.202 x the kW of panels being installed and then round down the result. So for 5kW of panels it is 15.202 x 5 = 82.92, round down makes 76 STCs for 5kW of panels.

On Jan 1st 2021 it will reduce to 13.82 x kW of panels
On Jan 1st 2022 it will be 12.438 and so on until it reduces to zero

Whilst the number of STCs reduces each year, the value of them bounces up and down, as they are bought and sold on the energy market and therefore supply and demand rules apply

If there is a sudden surge in demand for solar that means more STCs are created.
More STCs means that there are more sellers than buyers, so the price goes down.
Sudden STC price falls happen. In 2018 the STC price dropped from $40 to $25 in a week.

The other consideration about STCs is that the solar retailer buys them from you and gves you an upfront discount.
In truth we would prefer not to. We would prefer you to go and register tham (48 cents cost each)
We would prefer you to do all the paperwork and handle all the audits
We would prerer you to sell them yourself on the energy markets or to an aggregator so we aren't exposed to risk
But that's not how it usually works so this is how they are dealt with.

A typical mid range solar system, Huawei inverter, smart meter and LonGi panels for example sells for about $8,000
That includes GST of $727
Then we deduct the STCs that we are buying from you. As you aren't GST registered you sell them to us excluding GST.
So $8,000 is reduced by $3,700, making the price you pay $4,300.
However, that price includes the original $727 of GST.
So of the $4,300 price, 16.9% of it is GST.

Here are some answers to commonly asked questions about STCs

Can I get STCs on the same house, if I've claimed before?
Yes. If you install a complete new system, with CEC approved inverter and panels and installed by CEC accredited person.

Can I add more new panels and claim STCs on them
Yes, as long as the inverter is still on the "CEC Approved Inverter list"

If I'm in Melbourne do I get the same STCs?
No. Less sun than Perth, so fewer STCs.


Feed-In Tariffs refer to what you get paid for surplus power made by your solar during the day that wasn't needed at the time it was made. In Perth it is now an average of 4 cents per kWh (3 cents to 3pm and 10 cents after 3pm, averages out at 4 cents usually). Synergy call it the Renewable Energy Buyback Scheme (REBS).

A typical 5kW inverter and 6.6kW of panels in Perth produces an average 27-32kWh of power per day depending on roof orientations.

Breaking that down a bit, on a North facing roof, 6.6kW of panels will make on average...
1.1 kWh before 8am.
5.5 kWh between 8am and 10am.
8.7 kWh between 10am and 12pm.
8.8 kWh between 12pm and 2pm.
6.2 kWh between 2pm and 4pm.
1.6 kWh between 4pm and 6pm.
...and 0.05kWh after 6pm.

That's worth knowing when it comes to working out when to run your pool pump, bake a cake, turn the A/C on etc.

For most homes, a daytime use of between 4kWh and 12kWh is entirely normal, so the solar is making far more power than the house can use up.

Whatever can't be used in the house is pushed back to the Synergy meter by the inverter which records the 'surplus'.

Every ten minutes the Synergy meter adds up the total power it has received from the solar inverter and the total power drawn from the street and subtracts one from the other to work out whether you owe them money, or vive versa.

If we take a typical example of a home that uses 10kWh of solar and exports 20kWh then at current Synergy prices that works out as:
10 x 28.83 cents + 20 x 4 cents = $3.68 a day or $1,344 a year.

Better quality 'N' type solar cells degrade more slowly than regular 'P' type cells and after 25 years, its entirely likely that the 'N' type celled panels will be making 10% more power than the 'P's.

25 years is a very long time though, and for at least for the first ten years, there will be next to no difference in output from any 6.6kW of solar panels.

Half-Cell panels work a bit better in heat and low light and might give you a 1% more power, micro inverters and optimisers might give an unshaded roof another percent or two extra, but....

Always keep in mind that almost every single solar install produces a lot of surplus power already, so squeezing an extra 1-3% more out by buying expensive gear is really only gaining you pennies.

3% extra on 32kWh a day is 1kWh. 1kWh extra, exported, is worth 4 cents a day or $15 a year. Is it worth spending thousands extra for $15 a year return?


Financing solar purchases is surprisingly rare in our experience and yet we are really not sure why. Totally legit unsecured Green Energy Loans have interest rates of about 6% and setup fees of $150. The 'Interest free' deals require the retailer to load their prices by $600 or so to cover the fees charged by the financer, so in reality, you ultimately pay less and have much more flexibility going for a green loan from folks like Community First Credit Union. Cheapest way though if you can't pony up the cash is to talk to your bank and try to put it on your mortgage.