Time of use or flat rate in South Australia, with solar
On a flat tariff every unit costs the same. On time of use, South Australia charges about 56.3c at peak and 32.8c off peak against a flat 42c. Which suits you depends on when you use power and whether you have storage.
What is different about South Australia
South Australia has the most expensive electricity of the 8 at 42c a unit, which raises what every unit you avoid buying is worth, and one of the lowest feed-in tariffs at 1c, so exporting is close to giving power away and self-consumption carries the entire case. It averages 5 peak sun hours a day.
The rates side by side
Flat: about 42c a unit, all day.
Peak: about 56.3c, which is 1.34 times the flat rate.
Off peak: about 32.8c.
There is also a daytime window at about 17.2c, sometimes called a solar sponge rate, which is deliberately cheap because there is so much rooftop generation at that hour. That window is the cheapest grid power available here and it is worth knowing about even without solar.
What it means with solar on the roof
Solar generates in the middle of the day and most households use most of their power in the evening. On time of use that evening consumption is charged at the peak rate, so the power solar cannot cover is the most expensive power you buy. That cuts both ways: it makes the gap solar leaves behind more painful, and it makes a battery that covers the evening worth more.
The honest answer
Time of use suits a household that can genuinely move load and is out during the peak window. It punishes a household that is home in the evening and cannot shift anything. With a battery covering the evening peak it usually wins. Without one, in South Australia, it is a close call and worth modelling on your own bill rather than taking a rule of thumb.
| Household uses | Their bill a quarter | System | After rebates | Saves a year | Pays for itself |
|---|---|---|---|---|---|
| 10 kWh | $482 | 6.6kW solar | $6,250 to $8,250 | $480–$730 | 10+ years |
| 15 kWh | $673 | 10–13kW solar | $8,000 to $13,000 | $740–$1,120 | 9–10+ years |
| 22 kWh | $941 | 10–13kW solar | $8,000 to $13,000 | $1,030–$1,540 | 6–10 years |
| 30 kWh | $1,247 | 10–13kW solar | $8,000 to $13,000 | $1,360–$2,030 | 5–8 years |
Panels only on a flat tariff, after rebates, for reference.
$5,000 difference.
That is the gap between two quotes for the same 6.6kW system in South Australia, in the same week. Not build quality, not a better job. Overheads, how full the diary is that month, and what the person at your kitchen table thinks you will agree to. On solar with a battery the same gap is $10,600.
Closing that gap is what I do. I already know what installers in your area are quoting this month for this equipment, so I get you the bottom of that range for the same system other companies charge thousands more for. It costs you nothing. The installer pays me, and only if you go ahead, which is why there is no reason for me to push you at a bigger system than you need or at a dearer installer.
Get your own numbers, then get them priced properly
The table above is four example households. Two minutes of questions gets you your system size, what it should cost after rebates in South Australia, and a ten-year projection built on your roof and your usage. Then I find the bottom of that price range for you.
Run my numbers, freeNo installer buys placement or ranking here, and nothing reaches an installer unless you ask.
Common questions
What is the peak electricity rate in South Australia?
About 56.3c a kWh on a time-of-use tariff, against roughly 42c on a flat rate. Off peak is about 32.8c.
Is time of use better with solar?
It depends on whether you can move load out of the peak window. With a battery covering the evening it usually wins; without one, and if you are home in the evening, a flat rate is often safer.
Does a battery earn more on a time-of-use tariff?
Yes, because it displaces power that would otherwise be bought at the peak rate of about 56.3c rather than the flat 42c.