Online savings calculators ask for a postcode and a rough bill, then produce a confident figure to two decimal places. The inputs that actually decide the answer — when you use power, what your roof faces, what shades it, what your retailer pays for exports — are the ones they quietly assume. So here is the arithmetic instead, done with your own numbers.
Or send us a bill and we will do itThis will take about ten minutes and it will make every quote you receive afterwards far easier to judge — ours included.
Find what you pay per kilowatt-hour
It is on your bill, usually as a usage rate in cents per kilowatt-hour, sometimes with peak, shoulder and off-peak tiers. Write down each rate and the daily supply charge separately, because solar reduces the first and does nothing at all to the second.
Find what your retailer pays you for exports
The feed-in tariff, on the same bill. Put it next to your usage rate. The gap between those two numbers is the entire economic case for using your own generation rather than selling it, and it is why storage has become more attractive as feed-in tariffs have fallen.
Work out how much of your usage is in daylight
This is the number that decides everything, and the one no calculator can guess. If your meter is smart, your retailer can give you interval data showing consumption hour by hour. If not, think honestly about a normal weekday: who is home, what is running, and when.
Split your bill into daytime and after-dark
Roughly is fine. Solar without storage attacks the daytime half at your usage rate and the after-dark half only at the feed-in rate. A household that is empty until six gets a very different answer to one with someone home all day, on identical roofs.
Now compare that against a real quote
With those four figures in hand, an itemised quote becomes something you can actually check rather than something you have to trust. Hardware, labour, and the STC rebate on its own line. That is the point at which the sums mean something.
A postcode cannot see your roof.
Two houses in the same street, same orientation, same bill, can produce answers that differ by years of payback — because one has a neighbour’s gum tree over the western array and the other does not. Shading, pitch, switchboard condition and whether the meter needs reconfiguring are all site facts, and a form cannot ask about what it does not know to look for.
Which is the same reason we do not publish a headline price. A number produced before anyone has looked is a guess wearing the clothes of a quote.
What we look at that a form cannot
- Actual interval data, where your meter and retailer can provide it.
- Shading across the day and across the seasons, not just at noon in December.
- Roof pitch, orientation, structure and access — all of which move the labour cost.
- Switchboard condition, and whether a meter reconfiguration is needed.
- Whether a battery, a charger or neither is the better use of the next dollar.
We will model your consumption and come back with an itemised quote you can check line by line against the sums you just did yourself. No obligation, and no salesperson in your kitchen.