Interactive tool

Work out what solar would actually save you.

Set your system size, power usage and tariffs, and see estimated annual savings, payback period, monthly generation and your bill before and after. Every assumption is editable and shown in full below.

  • Australian state sun-hour data
  • Battery modelling
  • Bill before vs after
  • 25-year projection
  • No data leaves your browser

Your details

Adjust anything here and the numbers on the right update instantly.

Where are you? 5.2 sun hrs/day

Average daily peak sun hours. You can override this in advanced settings.

System size 6.6 kW

A typical Australian home installs between 6.6 kW and 13 kW.

Average daily power use 18 kWh

Check any recent bill for daily average usage. A typical home sits near 16–20 kWh.

When do you use most power?

This sets how much solar you use directly rather than exporting. Direct use is worth far more.

Add a battery? No battery

Usable capacity in kWh. A battery stores surplus solar so you buy less at night.

Before any rebate.

STC value varies by zone, system size and certificate price.

Set this only if you have confirmed an applicable scheme.

Losses from heat, wiring, inverter, dust and orientation.

Estimated savings in year one
$0 / year
Payback in —
0
kWh generated per year
$0
Net system cost after rebate
$0
Net benefit over 25 years
0 t
CO2 avoided over 25 years

Your power bill, before and after

Now, without solar$0 / yr
With this system$0 / yr

Estimated generation by month

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Where the saving comes from

Solar used directly in the home0 kWh
Stored in battery and used later0 kWh
Exported to the grid0 kWh
Value of power you no longer buy$0
Feed-in credit for exports$0
Total year-one saving$0
These are estimates from the inputs above, not a quote. Real output depends on roof orientation, pitch, shading, equipment and your retailer’s tariffs.
How the maths works

Every number here is calculated in the open

No hidden multipliers. If you disagree with an assumption, change it in advanced settings and watch the result move.

Annual generation

kW x sun hours x 365 x performance ratio. Peak sun hours come from the city you pick; the performance ratio defaults to 0.8 to cover heat, inverter, wiring and dust losses.

Direct use vs export

Your usage pattern sets the share of daily power consumed while the sun is up — 50%, 32% or 18%. Solar covers that first, and only the surplus is exported.

Battery

A battery captures surplus up to its usable capacity each day and discharges it into your evening load. Charging/discharging losses are included using the battery-efficiency setting.

Savings and payback

Savings equal power you no longer buy plus feed-in credit. Fixed daily supply charges remain payable, and payback divides net system cost by year-one energy savings.

25-year projection

Each year applies your electricity price rise and panel degradation, then subtracts the net system cost. Defaults are 3% and 0.5% per year.

Emissions avoided

Generation multiplied by roughly 0.68 kg of CO2 per kWh, a reasonable figure for Australian grid electricity, then summed across 25 years.

Questions

Reading the result

This is an estimate, not a quote or financial advice. The figures depend entirely on the inputs above and on general assumptions that will not match every property. Roof orientation, pitch, shading, roof condition, switchboard upgrades, equipment quality, retailer tariffs, rebate eligibility and your actual usage pattern all change the outcome, sometimes substantially. Rebate values in particular change over time and by location. Before committing, get a written quote from an accredited installer who has inspected your property, and confirm current tariffs with your electricity retailer.

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