Solar power production calculator in Australia

 

To use the solar power production calculator below, simply select your City and then enter the kW of panels in the second column.
e.g. if you have 3.3kW of panels on West and 3.3kW of panels on East, enter 3.3 against both W and E.
At the bottom of the table you can change the Export (FIT) price as well as the electricty price you pay.
The bill savings calculator below will automatically adjust itself based on what you enter.

Select a City :

Perth
kW of panels (e.g. 6.6) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Avg. Per Day % to N

Export Price :

Electricity Price :

Annual electricity bill savings

Daytime power consumption Savings Year 1 Savings Per Bill


'P' type Solar cells degrade in output every year by an average 0.68%, 'N' type cells typically by about 0.4% a year.

However, as power prices most certainly go up by considerably more than that, your financial return is very likely to increase each year even if the solar panels are making slightly less power.

The most important consideration about saving money from solar is WHEN you use power in your home.

As you can see from the tables below an 'afternoon sun' West facing installation of solar panels doesn't really help you power your aircon much when you get home from work.

For a typical 6.6kW install of panels on a West facing roof...
17% (4.6kWh) of the solar power is made before 10am.
74% (19.8kWh) between 10am and 4pm.
9% (2.4 kWh) is made after 4pm

The production story for a 6.6kW system with a North or East facing roof isn't really very much different to West...
21% (6.7kWh) on North, 30% (8.8kW) on East, of the solar power is made before 10am.
74% (23.5Wh) on North, 67% (19.6kWh) on East, between 10am and 4pm.
5% (1.6 kWh) on North, 3% (0.9kWh) on East is made after 4pm.

So, no matter which way the panels on your roof face...
Are you able to use 20kWh of solar power in your house between 10am and 4pm?
Most people would say no to that.
Maybe on a hot weekend, but most of the time, it's more likely 6-15 kWh depending on whether they have a pool pump or not.

So, this how it typically works out.... The 6.6kW solar makes about 30kWh per day.
The house uses 10kWh of it, and exports the other 20kWh
The electricity bill saving (at 2019 Synergy prices) is 10 x 28.83 cents + 20 x 7.135 cents = $4.31 a day or $1,573 a year.

Why are we all buying solar installs that make three times as much power as we need?

There are two simple reasons.

Generally speaking the Goverment incentive (STCs) means that it costs very little extra to have a 6kW system instead of 2kW one.
People often think to the future and say, I want plenty of surplus so that I can store it in batteries when they are affordable and then use it to power my house, charge my electric car etc

The next thing we look at is how the sun transits across the sky through the seasons and WHEN during the day solar power is made.

Most people know that the only two days of the year that the sun actually rises due East and sets due West are March 21st and September 21st, but it surprises a great many people how FAR South East the sun rises in Summer, and sets in the South West. In fact in January the sun is due West at about 3.30pm !!

You can also see that the arc is narrow, meaning the sun is more 'overhead' than the Winter picture shown underneath. It barely gets above Northbridge in the picture.

July image below. The Sun is rising in the East North East and setting West North West.

Notice how low in the sky the sun is with the top of the arc at Noon stretching up as far as Landsdale in the North in this picture.

Being so low in the sky greatly reduces solar production.

The tables below show WHEN the solar power is produced, every two hours, from dawn until dusk.

East facing roof

86% of the solar production is achieved, on average across the year by 2pm and over 97% by 4pm
Summer power production is quite evenly spread from dawn to 4pm

Winter power production is very concentrated to between 10am and 2pm

 
Dawn to 8am
8am to 10am
10am to Noon
Noon to 2pm
2pm to 4pm
4pm to 6pm
6pm to Sunset
Jan
15%
23%
25%
21%
13%
3%
0%
Feb
12%
23%
25%
21%
14%
4%
1%
Mar
8%
25%
28%
23%
13%
2%
0%
Apr
7%
26%
30%
24%
11%
12%
0%
May
1%
26%
36%
27%
9%
1%
0%
Jun
1%
15%
39%
34%
10%
1%
0%
Jul
0%
15%
33%
35%
14%
3%
0%
Aug
3%
26%
33%
26%
10%
2%
0%
Sep
3%
24%
34%
26%
10%
3%
0%
Oct
7%
21%
33%
23%
13%
3%
0%
Nov
16%
25%
26%
21%
11%
2%
0%
Dec
17%
23%
24%
21%
12%
2%
1%
 
Ave
7.55%
22.75%
30.49%
25.06%
11.64%
2.33%
0.18%
Cum
7.55%
30.3%
60.79%
85.85%
97.49%
99.82%
100%

 

North facing roof

As with the East facing roof, North produces virtually no power after 6pm year round,
and virtually nothing before 8am in Winter

Production is very evenly spread, year round, from 8am to 4pm

75% of daily power, on average, is produced before 2pm, and 95% before 4pm

 
Dawn to 8am
8am to 10am
10am to Noon
Noon to 2pm
2pm to 4pm
4pm to 6pm
6pm to Sunset
Jan
5%
18%
24%
24%
20%
9%
1%
Feb
4%
17%
23%
24%
22%
9%
1%
Mar
3%
17%
25%
27%
20%
8%
0%
Apr
3%
17%
26%
27%
21%
6%
0%
May
1%
15%
29%
30%
22%
3%
0%
Jun
0%
15%
30%
31%
21%
4%
0%
Jul
0%
14%
30%
31%
22%
3%
0%
Aug
1%
17%
30%
31%
18%
3%
0%
Sep
3%
18%
28%
28%
16%
6%
0%
Oct
6%
20%
28%
27%
17%
2%
0%
Nov
7%
21%
27%
26%
16%
2%
0%
Dec
7%
19%
24%
24%
19%
7%
0.%
 
Ave
3.36%
17.23%
27.16%
27.45%
19.51%
5.11%
0.18%
Cum
3.36%
20.59%
47.75%
75.2%
94.71%
99.82%
100%

 

West facing roof

Worried about late afternoon shade from trees hitting your West roof after 6pm ?

Don't be...Only 0.45 % of your production happens after 6pm, whereas 2.88% HAPPENS BEFORE 8AM.

Over 40% of your average production happens before mid day and 90% by 4pm.

 

 
Dawn to 8am
8am to 10am
10am to Noon
Noon to 2pm
2pm to 4pm
4pm to 6pm
6pm to Sunset
Jan
5%
15%
22%
23%
21%
12%
2%
Feb
3%
15%
23%
26%
22%
10%
1%
Mar
2%
14%
23%
26%
22%
12%
1%
Apr
2%
14%
25%
28%
21%
10%
0%
May
1%
14%
27%
30%
22%
7%
0%
Jun
0%
13%
29%
26%
19%
13%
0%
Jul
0%
15%
29%
30%
22%
4%
0%
Aug
1%
4%
28%
30%
20%
8%
0%
Sep
2%
14%
25%
28%
21%
9%
0%
Oct
4%
15%
24%
27%
22%
9%
0%
Nov
5%
17%
24%
25%
20%
9%
0%
Dec
7%
10%
16%
28%
24%
13%
1%
 
Ave
2.88%
14.05%
24.58%
27.09%
21.39%
9.57%
0.45%
Cum
2.88%
16.92%
41.51%
68.59%
89.98%
99.55%
100%