Free Solar System and Battery

There are many adverts stating that “the federal government is offering eligible homeowners up to $7,000 toward the cost of installing rooftop solar panels on their homes.
This incentive can be coupled with options (Solar Battery?) that enable you to reduce your power bill and essentially get the solar system for free.”

But, be aware of this:

The calculation to make it FREE, is that what you save in the future, will cover the initial cost.

How long it takes to make it effectively free, will depend on the size of system you buy, together with how much you get back in rebates, and how much you save using free electricity while the sun shines. A battery addition at about $12,000 will help to utilise excess free electricity, but will extend the time before the system effectively becomes free.

An example using my own solar installation.

In August 2018, I paid $2,290 for 3.5 kwh solar system. This cost was AFTER all government rebates.
This system saved me an average of $65 per month.
After 36 months, I had saved $2,329.73.
So, in August 2021, I could say that the cost of my system was effectively FREE.

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  • $1,136.82 of the savings were from the use of Free Electricity.
  • $1,192.91 of the savings were from the sale of my solar back to the supplier.

How would a battery have helped me?

Based on my power usage, an 8kWh battery is the size they suggest for me, and the rebate is stated to be $4,800. (The $7,000 rebate often quoted is the maximum available, presumably for an even larger battery system.)
I also checked at a higher daily power consumption, and found that a 12kWh system gets a rebate of $6,000.

I checked the price for an 8kWh battery and inverter, and this came to an average price of $11,760, fully installed. That would be $6,960 after the $4,800 rebate.

That cost of $6,960 would save me about an extra $35 per month on my electricity bill, assuming my savings increased to $100 per month.

With that extra $35 per month saving, the system would become FREE after another 200 months. So, in August 2038, I would be able to say it was free.

But… I haven’t included the interest cost on borrowing that upfront cost…

Nor have I included the battery replacement cost after ?? years. How long do these batteries last?

A quick google search gave me this:

How Long Does a Solar Battery Last?

Home solar battery units last anywhere between 5 and 15 years.

If I get the best one, I would need a new battery in 2037, just before the old one paid for itself, assuming the best battery cost the average battery price.

If I got the worst one, I would need another battery in 2027, and another in 2032, and yet another in 2037.  Ouch!

Before buying a solar battery, I would need to look into this much more.

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