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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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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 sizeUp front cost for the quoted solar systemAnnual solar system output in kWhPrice per kWh you currently pay for electricityTotal cost (including NPV of replacement inverter)Total electricity savingsNet savingsPayback timeLevelised 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.

Solar power savings calculator input variables
FieldVariable
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
solar savings calculator results example

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

Items Covered:
Refrigerator
Energy efficient LED lights
(no more than 10)
LCD TV
Appliances in standby mode
Washing Machine
(1 load per week)
Dishwasher
(2 loads per week)

Items Covered:
Refrigerator
Downlights lights
(10 to 20)
LCD TV
Appliances in standby mode
Washing Machine
(Up to 5 loads per week)
Dishwasher
(Up to 5 loads per week)
Desktop PC
Small air-conditioning unit

Items Covered:
Refrigerator
Downlights lights
(20+)
2+ LCD TV
Appliances in standby mode
Washing Machine
(Up to 5 loads per week)
Dishwasher
(Up to 5 loads per week)
Cloths dryer
(Up to 5 loads per week) Desktop PC
Large air-conditioning unit

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.

3kW4kW5kW
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