Calculate your payback
The price, grid rate and feed-in fill in from this month's index for the city you pick and the state's typical tariffs; overwrite them with the figures on your quote and your bill. Self-consumption is the share of solar output you use at home rather than export; 35 per cent is typical for a household out during the day. Nothing you enter leaves your browser.
How the saving is made
A solar system saves money two ways. Every kWh you use at home while the panels are producing replaces a kWh you would have bought at the grid rate, 34 cents in New South Wales on our data. Every kWh you do not use is exported for the feed-in tariff, 4 cents. The split between the two, the self-consumption share, matters more than any other input: a kWh used at home is worth 8.5 times a kWh exported at these rates. Payback is the price divided by the year-one saving. The 25-year figure adds up each year's saving with output falling 0.5 per cent a year, the warranted degradation rate of a mainstream panel, and subtracts the price; it assumes today's tariffs for the whole period.
Worked example in full: 6.6 kW in Sydney
The Sydney standard offer for 6.6 kW is $6,170 in October 2026, after the STC discount at $39 per certificate. Sydney's yield is 1,424 kWh per kW per year, so the system makes 9,398 kWh in year one. At 35 per cent self-consumption, 3,289 kWh are used at home, worth $1,118 at 34 cents, and 6,109 kWh are exported for $244 at 4 cents: a year-one saving of $1,363, or $26 a week. $6,170 divided by $1,363 is 4.5 years.
Over 25 years, with output falling 0.5 per cent a year to 88.7 per cent of year one by year 25, the system makes 221,388 kWh and saves $32,101, leaving $25,931 after the price. That is a lifetime cost of 2.8 cents per kWh against a grid rate of 34 cents. The curve below is the net position each year: it starts at minus $6,170, crosses zero in year 4.6 and ends at $25,931.
The same money at the Sydney premium offer of $7,284 pays back in 5.3 years and nets $24,817; a 10 kW system at $8,780 makes 14,240 kWh, saves $2,065 in year one, pays back in 4.3 years and nets $39,858: the extra panels are cheaper per watt, which outweighs the fact that most of their output is exported at 4 cents.
Payback by capital city, 6.6 kW standard offer, October 2026
Same method, each capital's own price, yield and state tariffs, 35 per cent self-consumption. Adelaide pays back fastest at 3.6 years and Darwin slowest at 6.0; the gap comes from price, sun and the feed-in tariff together, not from any one of them. Tariffs are the typical state figures in our data; your own bill will differ, and the calculator takes your numbers.
| City | Price | kWh/kW/yr | Year 1 kWh | Grid / feed-in | Year 1 saving | Payback (yrs) | 25-year net | Lifetime c/kWh |
|---|---|---|---|---|---|---|---|---|
| Sydney | $6,170 | 1,424 | 9,398 | 34c / 4c | $1,363 | 4.5 | $25,931 | 2.8c |
| Melbourne | $6,218 | 1,314 | 8,672 | 29c / 3c | $1,049 | 5.9 | $18,501 | 3.0c |
| Brisbane | $6,756 | 1,533 | 10,118 | 30c / 5c | $1,391 | 4.9 | $26,015 | 2.8c |
| Perth | $5,294 | 1,606 | 10,600 | 33c / 2.75c | $1,414 | 3.7 | $28,008 | 2.1c |
| Adelaide | $5,812 | 1,533 | 10,118 | 40c / 3c | $1,614 | 3.6 | $32,202 | 2.4c |
| Canberra | $6,144 | 1,570 | 10,362 | 27c / 6c | $1,383 | 4.4 | $26,442 | 2.5c |
| Hobart | $7,544 | 1,278 | 8,435 | 30c / 9.28c | $1,394 | 5.4 | $25,303 | 3.8c |
| Darwin | $10,250 | 1,606 | 10,600 | 29c / 9.13c | $1,705 | 6.0 | $29,910 | 4.1c |
Self-consumption decides the result
Hold everything else at the Sydney example and move only the share of output used at home. At 20 per cent, a house empty all day, the saving is $940 and payback 6.6 years. At 50 per cent, someone home most days or a hot water timer set for midday, it is $1,786 and 3.5 years. At 70 per cent, which usually needs a battery or an electric car charged at home, it is $2,350 and 2.6 years. Moving a dishwasher, washing machine and pool pump to the middle of the day is free and shifts the share by 10 to 15 points on most homes.
| Self-consumption | Year 1 saving | Payback (yrs) | 25-year net |
|---|---|---|---|
| 20 per cent | $940 | 6.6 | $15,969 |
| 35 per cent | $1,363 | 4.5 | $25,931 |
| 50 per cent | $1,786 | 3.5 | $35,894 |
| 70 per cent | $2,350 | 2.6 | $49,177 |
What the curve leaves out
Three things make the real result better than the curve and three make it worse. Better: grid prices have risen faster than inflation for most of the last decade and the curve holds them flat; most feed-in tariffs are lower than the grid rate by a wider margin each year, so the value of using your own power rises; and a system usually outlasts 25 years. Worse: the inverter is likely to need replacing once, at roughly a tenth of the system price, in years 10 to 15; shading, a flat or south-facing roof, or an export limit cuts the yield below the city figure; and a retailer plan with a daily supply charge means the bill never reaches zero. A fair reading is that the curve is right to within a year or two of payback for a well-sited system on a typical tariff.
Payback is also not the only test. If the money would otherwise sit in an offset account, the finance page compares cash, loan and redraw; the solar panel cost pages show what a fair price is for each size, and the bill-based savings calculator starts from your quarterly bill instead of a system size.
Assumptions and sources in plain words
Prices are the Solar Choice installer offers for October 2026, standard tier, after STCs at $39 per certificate and GST inclusive; cities Solar Choice does not index use the nearest indexed capital, which the city list names. Yields are from the Clean Energy Council's per-city output table, cross-checked against Bureau of Meteorology solar exposure for each city's station, in kWh per kW per year, and already allow for inverter and wiring losses on an unshaded north-facing roof. Grid rates and feed-in tariffs are the typical figures for each state in our data, checked on 27 October 2026; they are starting points, and your bill is the source that matters. Self-consumption defaults to 35 per cent, degradation to 0.5 per cent a year, and the horizon is 25 years with no tariff change, no inverter replacement and no maintenance. Payback is the price divided by the year-one saving; the curve uses the same saving falling with degradation. The calculator runs in your browser, sends nothing to a server and stores nothing.
Solar payback questions
How long does solar take to pay for itself in Australia?
3.6 to 6.0 years for a 6.6 kW system at the October 2026 standard offer in the eight capitals, on 35 per cent self-consumption and typical state tariffs; Adelaide is fastest and Darwin slowest. Sydney is 4.5 years at $6,170.
How much does a 6.6kW solar system save per year?
$1,363 in Sydney in year one: 9,398 kWh of output, 3,289 kWh used at home at 34 cents and 6,109 kWh exported at 4 cents. At 50 per cent self-consumption the saving is $1,786; at 20 per cent it is $940.
What is the 25-year return on a solar system?
$25,931 net for the Sydney 6.6 kW example: $32,101 of savings over 25 years, with output falling 0.5 per cent a year and tariffs held flat, minus the $6,170 price. In the capitals the range is $29,910 to $32,202 between Darwin and Adelaide.
What does solar electricity cost per kWh over its life?
2.8 cents per kWh for the Sydney 6.6 kW example: $6,170 divided by 221,388 kWh over 25 years, against a grid rate of 34 cents. The premium offer at $7,284 works out to 3.3 cents.
Does a bigger system pay back faster?
4.3 years for 10 kW in Sydney against 4.5 for 6.6 kW on the same 35 per cent self-consumption: faster, because the 10 kW offer is cheaper per watt and that outweighs the extra output being exported at 4 cents. The 10 kW system nets $39,858 over 25 years against $25,931, and the gap widens if the extra power charges a battery or a car.
Why is my payback different from the installer's figure?
$1,363 a year is what this page assumes for Sydney 6.6 kW; an installer quoting a 3-year payback on the same system is assuming a saving near $2,057, which needs self-consumption above 70 per cent, a higher grid rate or annual price rises. Ask for the self-consumption share, the tariffs and the yield behind the figure and type them into the calculator.