Variables that
affect your solar
system size needs

There are several variables that affect the optimal system size for a given property. The two key variables are: the amount of electricity consumed during daylight hours, and; whether or not you wish to store solar energy with a battery for use at night. These two variables are key to determining the optimal system size for your property.

The best place to start, is by checking your most recent electricity bill and seeing how much power you use each day. Then, the onus is on you to estimate how much power you consume during daylight hours. Our system size calculator below can then display your optimal system size.

solar system size calculator

Enter your property location and your daily electricity usage. If you don’t know your daily usage, you can calculate it here.
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Your system size results

This calculator provides an estimate of the system size needed to power your daily electricity consumption in your location.
Daily solar production:

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System size when only panels are installed

Consider the following scenario: The average Australian household consumes 18kW of electricity each day. If we use a house in Melbourne as an example, you would need a 5kW solar system to generate this amount of power. However, if the household only consumes 40% its electricity during daylight hours, there is no point installing such a large system. In this instance, a system that generates on average 7.2 kW (40% x 18 kW) of electricity per day would be sufficient. Therefore, a 2 kW system is likely to deliver the most cost effective solution and achieve the best financial payback; as the current, exceptionally low feed in tariffs, don’t encourage solar panel owners to generate excess power and export it to the grid.

Optimal size for solar panels and battery

A solar battery can store excess solar energy generated during daylight hours for use later at night, when the sun isn’t shining. If you are considering battery storage, you need to factor this into your system size equation. If we take the previous example, it may be beneficial to generate the 18 kWh of electricity it would take to power your property. If this were the case, you would need to upgrade the size of your solar panel system to 5 kW and add a battery capable of storing the excess solar power you generate during the day, for use at night, therefore storage capacity in excess of 10 kW would be required.

solar panel dimensions and roof area graphic

Physical area size required

A 5kW solar system may produce enough energy to power your home, but you may not have enough roof space for a system of that size. Solar panels for households typically come in the standard dimensions of 1.70m x 1.00m, that’s around 1.7m2 for every panel installed. However, the wattage output (W) of the panels will likely vary between 250W and 330W for a more efficient module.

As a guide, you’ll need 4 x 250W panels, or 3 x 330W for every 1kW of your solar system. If you’re considering a 5kW system, that’s between 15 and 20 solar panels that will require anywhere between 25.5 – 34m2 of roof space.

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Considerations
when determining
your system size

Our system size calculator determines how many solar panels you need to cover your average daily electricity use. However, in truth, there is far more to determining your optimal system size than this. It is though, a good starting point. We cover other factors that may influence your system size below.

System output should match your consumption habits

The system size you are quoted will normally be determined based on the average solar power generation potential of your property. If you are relying on your system to deliver a certain amount of power during cooler months, you need to be aware of this. For example, you’ll need a bigger system if you’re preparing to go off grid.

What are your solar goals

Personal preference and choosing a system to suit your lifestyle habits has a major influence on the system size you should select. You need to ask yourself, how much electricity do I want to power from solar energy?

Budget

Of course, the system size that you select may be determined by your budget and how much you can afford to pay upfront. So the cost of your solar panels and system is an important factor in selecting an appropriately solar system.

Off grid system size considerations

If you are planning on installing an off grid system, your solar power system will need to generate enough electricity to power your entire home, even during the cooler months with shorter daylight hours. You will need a larger system, in combination with battery storage, than if you were connected to the grid. You can calculate your off grid solar needs using our off grid solar calculator.

Maximise solar production or solar savings

If you have the option to stay connected to the grid, you can choose a system size that will maximise your solar production and your financial savings. The optimal size will depend on: daylight electricity consumption, and whether or not adding a battery to your system is financially viable, and; the price you pay for electricity. Our solar panel calculator defaults to the optimal system size for your property based on your selections; and combines system cost and savings information so that you can make an informed economic decision.