Comparing 10 roofs in 10 cities – Best and Worst locations

solar-power-comparison

Assessment: How do solar power output compare in ten largest Aussie cities.

No matter where you live and which way your roof is facing, how solar panels work is universal. Solar panels produce solar electricity the moment sunlight strikes on the surface of the panel. The amount of generation will vary with the intensity of sunlight, roof orientation, geography and the size of the system.

The solar panels produce DC current, which is passed through an inverter, which converts the electricity to AC current before supplying to your home. Because that’s the kind of electricity we receive from the grid as well. As long as the sun keeps shining solar panels continue to work.

In the nighttime, the solar panels do not work because there is no sun. However, if you really want to continue using solar power even after dark, you will need batteries.

The way solar panels work with batteries is; in the afternoon when the sun is out, while your home continues to draw power from the solar panels directly, some of the “surplus” power is diverted to charge the battery. Your inverter and charge controller will manage this.

Well, that’s a brief introduction of how solar panels work to generate electricity. If you want the long version of it, you can go to this page.

In this article, what I would like to do is make a comparison of solar power generation for different roof orientations across the major Australian cities. If you recall, north is the best roof orientation for maximum power generation. But, not everyone will have north roof. And not everyone lives in the same geographic location.

So, how good of a job solar panels on roof orientations other than north do? And how does your location compare to the other cities in the country?

This may be something of interest to you if you have recently started to dig more into solar power. It is always good to have perspective as well.

Before I present to you the graph with the data, few disclosures:

  • The data source is a combination of CEC and PVWATTS.
  • Because most residential roofs in Australia have 15° or 22.5° pitch (slope of the roof), I have chosen 20° as a middle ground for surface inclination/roof’s pitch while calculating the output from solar power system. Solar panels generate different amount of power for different surface inclination.
  • Solar output for each variation is expressed as a % of maximum output.
  • Maximum output for each location would be a north-facing roof whose surface inclination matches the earth’s latitude for that location.

And, here we go..

solar-production-australia
Source: Clean Energy Council (CEC), PVWATTS

I will make couple of observations for Hobart to explain how to read the graph.

Hobart

How good do solar panels work in Hobart? Well, regardless of roof orientation, they are going to produce the smallest amount of power of all locations in Australia.

If you have a south facing roof in Hobart, you get the idea on how hard the solar panels have to work to generate solar electricity. Annually, the production of a south roof at 20° pitch would be only 66% of the maximum output. And the max output would be from north-facing solar panel system at 42.88° pitch (Hobart’s latitude angle).

Now if you were wondering why Hobart’s north roof is only at 95% in my graph above, that’s because the standard roof pitch I have considered is 20° – which is 22.88° lower than the latitude.

In case of Darwin and Cairns, they produce the highest amount of solar electricity for any roof orientation. Both locations have better solar potential than other locations.

Table below has the numeric comparison of the chart.

 20° roof-pitch  

Brisbane

 

Sydney

 

Melbourne

 

Adelaide

 

Perth

 

Hobart

 

Alice Springs

 

Cairns

 

Canberra

 

Darwin

North 99% 98% 98% 98% 98% 95% 99% 100% 98% 100%
Northeast 97% 95% 93% 94% 95% 91% 97% 99% 95% 99%
East 89% 86% 84% 85% 87% 82% 90% 94% 86% 95%
Southeast 82% 77% 75% 77% 78% 71% 81% 89% 78% 90%
South 78% 73% 71% 74% 74% 66% 77% 86% 74% 86%
Southwest 81% 77% 76% 78% 78% 71% 81% 89% 78% 89%
West 88% 86% 87% 87% 87% 81% 89% 94% 86% 93%
Northwest 95% 95% 95% 96% 95% 91% 96% 99% 94% 98%

If you have a roof that is east, west or south facing, I have done a detail study of each roof orientation for solar power generation. You can find them in the link below.

West facing roof

East facing roof

East/West roof

South facing roof

If you are interested in solar, first thing you should do is understand your own power need. What size system do you need? ? Before you request for any solar quote it is important to figure this out on your own. In this post, I talk in more detail about how to size your solar system. 

If you have any questions regarding this post, please don’t hesitate to leave comments below.

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