How much energy do solar panels produce?

Fast read

The amount of electricity generated by a solar system varies based on several factors such as location, orientation, quality of panels, inverter type, and cleanliness.

The majority of a system's value comes from reducing electricity bills and utilising feed-in tariffs where excess energy is fed back into the grid for compensation.

The average feed-in tariff is between 5 to 12 cents per kWh. A 6.6 kW system producing on average each day 4 kWh per kW rated is capable of generating roughly 26.4 kWh on a sunny day and producing around 240,900 kWh over its 25-year lifespan.

If 70% of the electricity is utilised for reducing electricity bills and 30% is fed into the grid, the system can generate $43,843 in electricity bill savings and $5,782 in income for exported electricity over its lifetime.

How much energy should I expect my solar panels to produce?

The amount of energy your solar panels produce in their life cycle is one of the most critical considerations for making the initial investment worth it. When purchasing a solar system, you want it to perform efficiently throughout its entire life cycle, but what can stop it from doing so? 

Solar system size

The size of your solar system has the most significant influence on how much electricity is produced. As you would assume, a bigger system means more electricity. However, the size of your roof is the limiting factor. Your roof space limits the possible PV system size and amount of solar panels you can have. If you want your solar system to produce as much electricity as possible, you should cover as much of your roof as possible with panels.

Roof angle

The angle of your roof greatly influences how much energy your solar panels will produce. As solar panels produce energy from sunlight, the more direct sunlight they receive, the more electricity they will produce. In Australia, most roofs are pitched between 15 and 22.5 degrees. As a general calculation, 22 degrees is the best for solar panels in Australia, but as were are a very large country, these numbers do vary. 

If your roof is within the recommended range, there will not be a noticeable drop in electricity production. However, if your roof is flat, the energy your solar panels produce annually will decrease by approximately 15% and more in winter. 

solar panels installed on roof
The angle your panel is tilted can affect the overall output greatly

Orientation of the panels

The direction that your panels face will also have a significant influence on how much electricity is produced. In Australia, north-facing panels will be the most efficient. Your solar panels will produce approximately 13% less energy if facing East or West, with a further drop off if facing South, to around 35% less in production than a panel pointing true North.  So please remember a South-facing roof will produce only around 60 to 65% of your north-facing roof output. 

Panel quality

Like most products, the higher the quality, the better the performance. High-quality panels perform better in low light and in temperatures over 25 degrees Celsius.  They can convert a higher percentage of light into electricity. This is consistent across all weather conditions too. Higher-quality panels will also degrade slower than low-quality panels. This means they will produce more energy over the decades. When purchasing panels, get them from an established and well-trusted company, not via a Facebook price beater. 

Cleanliness of panels

Solar panels are exposed to the environment 24/7. Therefore debris can and will gather on the panels, as well as dust and residue, decreasing their ability to produce energy. The cleaner your solar panels are, the more electricity they will produce. A good rule of thumb is to have your solar panels professionally cleaned at least every 1 to 2 years. 


As solar panels produce energy from sunlight, any shading will reduce efficiency and output, costing you money. If any trees, buildings or other obstructions cause shading on a panel, the amount of electricity it can produce will decrease.

solar panels installed on commercial property


Your location will also dictate how much energy your solar panels will produce. This is mostly due to different climates, sun intensity and overall sunlight hours. Below is a comparison of the average daily production of 1 kW of panels across major Australian cities and landmarks such as Alice Springs.


Average daily production per kW

of the solar system capacity

Adelaide4.2 kWh
Alice Springs5.0 kWh
Brisbane4.2 kWh
Cairns4.2 kWh
Canberra4.3 kWh
Darwin4.4 kWh
Hobart3.5 kWh
Melbourne3.6 kWh
Perth4.4 kWh
Sydney3.9 kWh

How much energy should you expect from the life cycle of a solar panel?

To find how much energy your solar panels will produce over their life cycle, follow along with these calculations. For our example, we will use a standard 6.6 kW system.

In our example we also assume that our north-facing panels on a standard pitched roof produce about 4 kWh of electricity per kW the system is rated.

For our example, therefore on average, the system will produce about 26.4 kWh daily.

Now we move to the life span and annual degradation of the system. Today’s industry standard is that a solar system will last 25 years, with a first-year degradation of 2% and an annual degradation of 0.35% for the next 24 years. For our example system, this would result in a total production of 228,625 kWh of electricity over its lifetime. 

While this is a complex calculation, when finished, you can also find how much you will save during the life cycle. In Australia, the average cost of electricity is 35 to 40 cents per kWh. Therefore, for every kWh your system produces, you are saving 35 to 40 cents. 

Furthermore, for the electricity that you do not use, you can be paid a feed-in tariff (FIT). Let’s say your FiT in our example is 10c.

A sample calculation for a solar-only system

Assuming that we use 50% of the power our example system produces and save 35c per kWh, the calculation will be 228,625 times 0.5 times 0.35. This equals $40,009.

For the remaining 450%, we would receive 10c per kWh from the FIT. We can find this revenue through the calculation 228,625 times 0.5 times 0.1. This equals $11,431.

Adding these together would save you $51,440 over 25 years.

You now want to deduct $3000 for maintenance and inverter repairs/replacements. Then you can calculate the overall net benefit solar will generate for you, your family and your business.

Please note these figures do not apply specifically to your PV system but have been spelt out to show you how beneficial solar can be.

So you can use these calculations to find how much you will save over the life cycle of your solar system. So while you cannot find the exact amount of energy your solar panels will produce during their life cycle, you can now ensure you get the most out of it by knowing what affects its production and potentially finding how much you will save.

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