Some years ago I crunched a lot of numbers and concluded that financially it was not worth installing rooftop solar. It would never pay for itself.
Then the prices began dropping rapidly, the systems got larger, and the Victorian government added its own $2500 rebate on top of the Federal government's.
So a 6.6KW system started to look attractive and in October last year we had one installed.
Cost installed including 5 KW inverter: $4690
Less $2500 rebate $2190.
So out of pocket for me $2190.
From now until around May next year our daily solar output will exceed our draw from the grid, and the surplus will be sold at 12 cents a kw.
Some figures:
In the last 36 days, we have sold 570 KW to the grid for $68.
We have bought 369 KW from the grid for $107.
The 570 KW we sold was surplus -- there would have been hundreds of other KW we generated and used ourselves.
January 2019 our biggest summer electricity use month, we bought 160.3KW, but sold 750 KWs.
January 2018 without solar, we bought 592KW.
August 2018 (pre- solar)
Bought 876KW
Sold 0
Net 876
August 2019 (with solar)
bought 665 KW
sold 218 KW
net buy 447KW (so a little over half as much as without solar)
We generate much more than we sell, but the figures I have are for what is sold as surplus to our own needs.
Our biggest user is the reverse cycle air conditioner. Yesterday where in Melbourne we froze around 12°, it was on from around 8 am to 10.30 pm, consuming 19 KW of power. We generated about 18 Kw, most of that was used by the air con, tv, etc, and a surplus 4 KW sold into the grid.
The Solax inverter sends a wifi signal to my router for access anywhere in the world through a portal, giving real-time statistics on electricity being generated, panel volts, grid voltage... We love looking at all that nerdy stuff.
Is it green?
In the last 12 months, we have saved 8.6 tons of carbon emissions.
We have "planted" 23.2 trees
It has yielded 8.6 megawatts of electricity.
The proliferation of daytime solar has given incompetent governments who have failed to give us the power we need by building power stations, a breathing space -- tiny but maybe enough.
However, this proliferation is providing headaches for power suppliers. All that unused electricity being fed into the grid is not under their control, causing irregular voltage. They can turn street transformers up or down somewhat, but in the future it will be an alarming problem with almost catastrophic technical consequences.
Our inverter will switch off if the grid voltage reaches 260 -- and we come close very often.
At 10.24 this morning grid voltage was 253.4 -- just 7 volts off.
Power bills: We hate the way power companies keep changing plans. A year ago we could have sold power at 20 cents a KW. Now, after government meddling, it is a flat 12 cents. The price we pay for a KW though is three times that much.
Our bills have reduced dramatically. One quarter we were $3 in credit.
Personal future problems will be the slowly declining panel output, the inverters are a weak link, and replacement costs are very high. Without the inverter, output is cut to zero. When grid power is cut for maintenance, our inverter shuts down and we have zero power. (we do have petrol generators on standby).
Battery storage: too costly to be worth considering now.
For all that, we love our panels. Even though they are extremely inefficient. For every 100 watts of sunshine power that falls on every square meter of panels, just 17% or so is generated as electricity. They are improving, but very slowly.
Hope these figures prove helpful.
Then the prices began dropping rapidly, the systems got larger, and the Victorian government added its own $2500 rebate on top of the Federal government's.
So a 6.6KW system started to look attractive and in October last year we had one installed.
Cost installed including 5 KW inverter: $4690
Less $2500 rebate $2190.
So out of pocket for me $2190.
From now until around May next year our daily solar output will exceed our draw from the grid, and the surplus will be sold at 12 cents a kw.
Some figures:
In the last 36 days, we have sold 570 KW to the grid for $68.
We have bought 369 KW from the grid for $107.
The 570 KW we sold was surplus -- there would have been hundreds of other KW we generated and used ourselves.
January 2019 our biggest summer electricity use month, we bought 160.3KW, but sold 750 KWs.
January 2018 without solar, we bought 592KW.
August 2018 (pre- solar)
Bought 876KW
Sold 0
Net 876
August 2019 (with solar)
bought 665 KW
sold 218 KW
net buy 447KW (so a little over half as much as without solar)
We generate much more than we sell, but the figures I have are for what is sold as surplus to our own needs.
Our biggest user is the reverse cycle air conditioner. Yesterday where in Melbourne we froze around 12°, it was on from around 8 am to 10.30 pm, consuming 19 KW of power. We generated about 18 Kw, most of that was used by the air con, tv, etc, and a surplus 4 KW sold into the grid.
The Solax inverter sends a wifi signal to my router for access anywhere in the world through a portal, giving real-time statistics on electricity being generated, panel volts, grid voltage... We love looking at all that nerdy stuff.
Is it green?
In the last 12 months, we have saved 8.6 tons of carbon emissions.
We have "planted" 23.2 trees
It has yielded 8.6 megawatts of electricity.
The proliferation of daytime solar has given incompetent governments who have failed to give us the power we need by building power stations, a breathing space -- tiny but maybe enough.
However, this proliferation is providing headaches for power suppliers. All that unused electricity being fed into the grid is not under their control, causing irregular voltage. They can turn street transformers up or down somewhat, but in the future it will be an alarming problem with almost catastrophic technical consequences.
Our inverter will switch off if the grid voltage reaches 260 -- and we come close very often.
At 10.24 this morning grid voltage was 253.4 -- just 7 volts off.
Power bills: We hate the way power companies keep changing plans. A year ago we could have sold power at 20 cents a KW. Now, after government meddling, it is a flat 12 cents. The price we pay for a KW though is three times that much.
Our bills have reduced dramatically. One quarter we were $3 in credit.
Personal future problems will be the slowly declining panel output, the inverters are a weak link, and replacement costs are very high. Without the inverter, output is cut to zero. When grid power is cut for maintenance, our inverter shuts down and we have zero power. (we do have petrol generators on standby).
Battery storage: too costly to be worth considering now.
For all that, we love our panels. Even though they are extremely inefficient. For every 100 watts of sunshine power that falls on every square meter of panels, just 17% or so is generated as electricity. They are improving, but very slowly.
Hope these figures prove helpful.

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