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.

Solar Payback Calculator

Solar Panel Calculator

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.

Solar power savings calculator input variables
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

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.

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