Solar Power System Payback Calculator
The tables on this page have been generated using the Solar Payback Calculator on the SolarQuotes.com.au website, for more accurate and up to date results visit SolarQuotes.com.au and enter your own data.
New South Wales over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 2,847 kWh | 30c | $4,700 | $44,521 | $39,821 | 8 Years | 8.76c per kWh | 15.96% |
| 3kW | $4,500 | 4,270 kWh | 30c | $5,300 | $68,348 | $63,048 | 7 years | 6.59c per kWh | 20.30% |
| 5kW | $7,000 | 7,117 kWh | 30c | $7,800 | $114,850 | $107,050 | 6 years | 5.82c per kWh | 22.54% |
| 7kW | $9,000 | 9,964 kWh | 30c | $9,800 | $161,802 | $152,002 | 5 years | 5.22c per kWh | 24.70% |
| 10kW | $12,000 | 14,235 kWh | 30c | $12,800 | $232,237 | $219,437 | 5 years | 4.77 per kWh | 26.66% |
ACT Canberra over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 3,139 kWh | 30c | $4,700 | $42,604 | $37,904 | 8 years | 7.95c per kWh | 15.82% |
| 3kW | $4,500 | 4,708 kWh | 30c | $5,300 | $65,474 | $60,174 | 6 years | 5.98c per kWh | 20.20% |
| 5kW | $7,000 | 7,847 kWh | 30c | $7,800 | $110,059 | $102,259 | 6 years | 5.28c per kWh | 22.46% |
| 7kW | $9,000 | 10,986 kWh | 30c | $9,800 | $155,094 | $145,294 | 5 years | 4.73c per kWh | 24.65% |
| 10kW | $12,000 | 15,695 kWh | 30c | $12,800 | $222,653 | $209,853 | 5 years | 4.33c per kWh | 26.63% |
Victoria over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 2,628 kWh | 30c | $4,700 | $41,302 | $36,602 | 9 years | 9.49c per kWh | 15.08% |
| 3kW | $4,500 | 3,942 kWh | 30c | $5,300 | $63,528 | $58,228 | 7 years | 7.14c per kWh | 19.18% |
| 5kW | $7,000 | 6,570 kWh | 30c | $7,800 | $106,810 | $99,010 | 6 years | 6.30c per kWh | 21.28% |
| 7kW | $9,000 | 9,198 kWh | 30c | $9,800 | $150,542 | $140,742 | 6 years | 5.66c per kWh | 23.30% |
| 10kW | $12,000 | 13,140 kWh | 30c | $12,800 | $216,140 | $203,340 | 5 years | 5.17c per kWh | 25.12% |
Tasmania over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 2,555 kWh | 30c | $4,700 | $33,843 | $29,143 | 10 years | 9.76c per kWh | 13.10% |
| 3kW | $4,500 | 3,832 kWh | 30c | $5,300 | $52,332 | $47,032 | 8 years | 7.34c per kWh | 16.81% |
| 5kW | $7,000 | 6,387 kWh | 30c | $7,800 | $88,155 | $80,355 | 7 years | 6.48c per kWh | 18.68% |
| 7kW | $9,000 | 8,942 kWh | 30c | $9,800 | $124,428 | $114,628 | 6 years | 5.82c per kWh | 20.47% |
| 10kW | $12,000 | 12,775 kWh | 30c | $12,800 | $178,845 | $166,045 | 6 years | 5.32c per kWh | 22.08% |
South Australia over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 3,066 kWh | 30c | $4,700 | $48,976 | $44,276 | 8 years | 8.14c per kWh | 17.37% |
| 3kW | $4,500 | 4,599 kWh | 30c | $5,300 | $75,039 | $69,739 | 6 years | 6.12c per kWh | 22.11% |
| 5kW | $7,000 | 7,665 kWh | 30c | $7,800 | $125,996 | $118,196 | 5 years | 5.40c per kWh | 24.58% |
| 7kW | $9,000 | 10,731 kWh | 30c | $9,800 | $177,402 | $167,602 | 5 years | 4.85c per kWh | 26.98% |
| 10kW | $12,000 | 15,330 kWh | 30c | $12,800 | $254,512 | $241,712 | 4 years | 4.43c per kWh | 29.16% |
West Australia over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 3,212 kWh | 30c | $4,700 | $43,693 | $38,993 | 8 years | 7.77c per kWh | 16.14% |
| 3kW | $4,500 | 4,818 kWh | 30c | $5,300 | $67,115 | $61,815 | 6 years | 4.84c per kWh | 20.60% |
| 5kW | $7,000 | 8,030 kWh | 30c | $7,800 | $112,789 | $104,989 | 6 years | 5.16c per kWh | 22.91% |
| 7kW | $9,000 | 11,242 kWh | 30c | $9,800 | $158,913 | $149,113 | 5 years | 4.63c per kWh | 25.14% |
| 10kW | $12,000 | 16,060 kWh | 30c | $12,800 | $228,099 | $215,299 | 5 years | 4.23c per kWh | 27.17% |
Northern Territory over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 3,212 kWh | 30c | $4,700 | $46,880 | $42,180 | 7 years | 7.77c per kWh | 18.73% |
| 3kW | $4,500 | 4,818 kWh | 30c | $5,300 | $71,895 | $66,595 | 5 years | 5.84c per kWh | 24.27% |
| 5kW | $7,000 | 8,030 kWh | 30c | $7,800 | $120,755 | $112,955 | 5 years | 5.16c per kWh | 27.19% |
| 7kW | $9,000 | 11,242 kWh | 30c | $9,800 | $170,065 | $160,265 | 4 years | 4.63c per kWh | 30.04% |
| 10kW | $12,000 | 16,060 kWh | 30c | $12,800 | $244,031 | $231,231 | 4 years | 4.23c per kWh | 32.65% |
Queensland over 30 years
| System size | Up front cost for the quoted solar system | Annual solar system output in kWh | Price per kWh you currently pay for electricity | Total cost (including NPV of replacement inverter) | Total electricity savings | Net savings | Payback time | Levelised cost of electricity (LCOE) | Internal rate of return (IRR) |
|---|---|---|---|---|---|---|---|---|---|
| 2kW | $3,900 | 3,066 kWh | 30c | $4,700 | $41,515 | $36,815 | 9 years | 8.14c per kWh | 15.50% |
| 3kW | $4,500 | 4,599 kWh | 30c | $5,300 | $63,848 | $58,548 | 7 years | 6.12c per kWh | 19.80% |
| 5kW | $7,000 | 7,665 kWh | 30c | $7,800 | $107,344 | $99,544 | 6 years | 5.40c per kWh | 22.02% |
| 7kW | $9,000 | 10,731 kWh | 30c | $9,800 | $151,289 | $141,489 | 5 years | 4.85c per kWh | 24.15% |
| 10kW | $12,000 | 15,330 kWh | 30c | $12,800 | $217,208 | $204,408 | 5 years | 4.43c per kWh | 26.09% |
Below is a list of the inputs you can enter in the calculator followed by an example of the results displayed in a easy to read graph.
| Field | Variable |
|---|---|
| State | e.g. NSW |
| System size | 1.5kW to 10kW |
| Cost of quoted system | $=??? |
| Annual output in kWh | ???=kWh |
| Current electricity price per kWh | kWh=cents |
| Display results in years (max 30) | 1 to 30 |
There are also some more advanced input options available to help refine your results even further such as: annual bill inflation, energy exported to grid, feed in tariff rate, feed in tariff length and system maintenance or repair costs.
The result is a graph similar to the one below and a list displaying:
- Total system cost
- Total power savings
- Net savings
- Payback time
- Cost of electricity
- Rate of return
What Size Solar Power System?
The average Australian three bedroom home will generally use about 11kWh to 18kWh of power per day.
As a general rule a 1kW solar power system will generate roughly 4kWh to 5kWh of power per day depending on the location of the system and how many actual power producing hours are in a day a 3kW solar system should be large enough to supply power to an average Australian home.
Your location can have a big effect on the actual viability of a solar power system, for example if you live on a wide open and flat area with no hills your solar panels will receive much more sunlight per day than if you live in a deep valley surrounded by mountains. During different times of the day, morning, midday and late afternoon go outside and see if the sun is striking your rooftop, and remember the solar panels only produce power when the sun is shining on them so in some cases a solar system may not even be worth installing if you only get a couple of hours sunlight in the middle of the day.
The table below shows a rough guide to solar system sizing.
| Solar System Size Guide | ||
|---|---|---|
| 1.5kW Small Home 1-2 People | 3kW Medium Home 2-3 People | 5kW Large Home 4+ People |
|
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Using the amount monthly kWhs from your utility bill, and the amount of sun hours your location receives, you can find the size of your system, in DC watts, needed to cover 100% of your usage.
|
Sun Hours
Monthly Usage |
< 3.0 | 3.5 | 4.0 | 4.5 | 5.0 | 5.5 | 6.0 | 6.5 |
| 50kWh | 0.7kw | 0.6kw | 0.5kw | 0.5kw | 0.4kw | 0.4kw | 0.3kw | 0. kw |
| 100kWh | 1.4kw | 1.2kw | 1.0kw | 0.9kw | 0.8kw | 0.8kw | 0.7kw | 0.6kw |
| 150kWh | 2.0kw | 1.7kw | 1.5kw | 1.4kw | 1.2kw | 1.2kw | 1.0kw | 0.9kw |
| 200kWh | 2.7kw | 2.3 kw | 2.0kw | 1.8kw | 1.6kw | 1.6kw | 1.4kw | 1.2kw |
| 250kWh | 3.4kw | 2.9kw | 2.5kw | 2.3kw | 2.0kw | 2.0kw | 1.7kw | 1.6kw |
| 300kWh | 4.1kw | 3.5kw | 3.0kw | 2.7kw | 2.4kw | 2.4kw | 2.0kw | 1.9kw |
| 350kWh | 4.7kw | 4.1kw | 3.5kw | 3.2kw | 2.8kw | 2.8kw | 2.4kw | 2.2kw |
| 400kWh | 5.4kw | 4.6kw | 4.1kw | 3.6kw | 3.2kw | 3.2kw | 2.7kw | 2.5kw |
| 450kWh | 6.1kw | 5.2kw | 4.6kw | 4.1kw | 3.6kw | 3.6kw | 3.0kw | 2.8kw |
| 500kWh | 6.8kw | 5.8kw | 5.1kw | 4.5kw | 4.1kw | 4.1kw | 3.4kw | 3.1kw |
| 550kWh | 7.4kw | 6.4kw | 5.6kw | 5.0kw | 4.5kw | 4.5kw | 3.7kw | 3.4kw |
| 600kWh | 8.1kw | 6.9kw | 6.1kw | 5.4kw | 4.9kw | 4.9kw | 4.1kw | 3.7kw |
| 650kWh | 8.8kw | 7.5kw | 6.6kw | 5.9kw | 5.3kw | 5.3kw | 4.4kw | 4.1kw |
| 700kWh | 9.5kw | 8.1kw | 7.1kw | 6.3kw | 5.7kw | 5.7kw | 4.7kw | 4.4kw |
| 750kWh | 10.1kw | 8.7kw | 7.6kw | 6.8kw | 6.1kw | 6.1kw | 5.1kw | 4.7kw |
| 800kWh | 10.8kw | 9.3kw | 8.1kw | 7.2kw | 6.5kw | 6.5kw | 5.4kw | 5.0kw |
| 850kWh | 11.5kw | 9.8kw | 8.6kw | 7.7kw | 6.9kw | 6.9kw | 5.7kw | 5.3kw |
| 900kWh | 12.2kw | 10.4kw | 9.1kw | 8.1kw | 7.3kw | 7.3kw | 6.1kw | 5.6kw |
| 950kWh | 12.8kw | 11.0kw | 9.6kw | 8.6kw | 7.7kw | 7.7kw | 6.4kw | 5.9kw |
| 1000kWh | 13.5kw | 11.6kw | 10.1kw | 9.0kw | 8.1kw | 8.1kw | 6.8kw | 6.2kw |
| 1050kWh | 14.2kw | 12.2kw | 10.6kw | 9.5kw | 8.5kw | 8.5kw | 7.1kw | 6.5kw |
| 1100kWh | 14.9kw | 12.7kw | 11.1kw | 9.9kw | 8.9kw | 8.9kw | 7.4kw | 6.9kw |
| 1150kWh | 15.5kw | 13.3kw | 11.6kw | 10.4kw | 9.3kw | 9.3kw | 7.8kw | 7.2kw |
| 1200kWh | 16.2kw | 13.9kw | 12.2kw | 10.8kw | 9.7kw | 9.7kw | 8.1kw | 7.5kw |
| 1250kWh | 16.9kw | 14.5kw | 12.7kw | 11.3kw | 10.1kw | 10.1kw | 8.4kw | 7.8kw |
| 1300kWh | 17.6kw | 15.0kw | 13.2kw | 11.7kw | 10.5kw | 10.5kw | 8.8kw | 8.1kw |
| 1350kWh | 18.2kw | 15.6kw | 13.7kw | 12.2kw | 10.9 kw | 10.9kw | 9.1kw | 8.4kw |
| 1400kWh | 18.9kw | 16.2kw | 14.2kw | 12.6kw | 11.3kw | 11.3kw | 9.5kw | 8.7kw |
| 1450kWh | 19.6kw | 16.8kw | 14. kw | 13.1kw | 11.7kw | 11.7kw | 9.8kw | 9.0kw |
| 1500kWh | 20.3kw | 17.4kw | 15.2kw | 13.5kw | 12.2kw | 12.2kw | 10.1kw | 9.3kw |
| 1550kWh | 20.9kw | 17.9kw | 15.7kw | 14.0kw | 12.6kw | 12.6kw | 10.5kw | 9.7kw |
Solar Panel Roof Space Calculator
If you have decided on the size of the system you want then you need to determine if there is enough space for the solar panels.
An average size for a 250W solar panel is around 1.7m x 1m so a surface area of 1.7m2, round that up to at least 2m2 to allow for access and installation.
The table below shows some system sizes and area required.
| 3kW | 4kW | 5kW |
|---|---|---|
| 12x250W Panels | 16x250W Panels | 20x250W Panels |
| 20m2 Roof Area | 27m2 Roof Area | 34m2 Roof Area |
| Daily Output 13 kWh | Daily Output 17 kWh | Daily Output 22 kWh |
