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What Is The Right Size Solar For My Home?

There are two ways you can think about solar sizing: in terms of total power output, or in terms of total footprint of the system (in area).

What is a solar array?

A solar array can be defined as solar panels arranged in a group to capture maximum amount of sun light to convert it into usable electricity. The idea of solar array came to light when it was conceived that the power produced by a solar panel was not sufficient enough for domestic or commercial purpose.

“Strictly speaking, a solar array only encompasses the ensemble of solar panels, the visible part of the PV (photovoltaic) system, and does not include all the other hardware, often summarised as balance of system (BOS),” says Wikipedia. “Moreover, PV systems convert light directly into electricity and shouldn’t be confused with other technologies, such as concentrated solar power or solar thermal, used for heating and cooling.”

So when we talk about solar size for your home, it is in the concept of solar array – group of solar panels to form an electrical circuit. And if you’re looking for a solar power system for your house, you want to think in terms of power output in kilowatt hour (kWh). To maximise your financial savings, the optimal-sized solar array is one with a large enough power kW to at least match your household’s energy usage.


Let’s see how this works in practice.

How do I calculate the right size solar array for my home?

One way to estimate how many solar panels you need is to use an online solar calculator or more accurately, to call in for a custom estimate. For the latter, you would need to contact your solar specialist. From there, they can determine the right solar size system accordingly with the information below:

  • Area code;

  • Average quarterly energy bill and consumption - energy provider;

  • Roof type and direction;

    • Clay/terracotta

    • Concrete tiles

    • Metal

    • Other

    • Shingles

    • Ground mount: If your roof isn’t a possibility for a solar array, you can install as ‘ground mount’.

  • Roof shading;

    • Partially shaded (can improve)

    • Partially shaded (cannot improve)

    • Severely shaded

    • Unshaded during peak hours

  • Roof slope;

    • Flat

    • Medium

    • Slight

    • Steep


From the information provided, you can approximate the system size in kW, annual production in kWh, and the long-term profit (savings less cost of the system).

How many solar panels are needed to power a house?

In 2017, the average Australian house consumes electricity amounting to 18 kW per day or 6570 kW per hour . For a typical household, to match that energy requirement, a 4.5 kW system solar system is required. Because every house and household is different, shading and roof slopes vary, and because some families use more energy than others, the number of solar panels your home needs is household-specific.

What is the minimum roof size for solar panels?

Today's typical 300+ watt (latest technology) panel is about 1500mm length x 900mm width x 40mm thickness and weighs in at about 18 kg. This varies from manufacturer to manufacturer . It is obvious the more panels that you can put on your roof space, in the right direction, you will be able to get maximum solar output from the system. Note also that the cost of the panel increases when the panel output capacity increases.

Solar quotes, a popular online solar blog says 'Bigger Is Better'. They recommend installing rooftop solar power as much your roof allows it or your budget allows. See full article here.


This begs the question, what's the maximum system output can be installed on my roof?

From this then one can determine how much solar is generated and consequently how much you can save. Essentially, how much you can save over the 20 years (that's how long the system should last), and the cost of the actual system, then you can determine whether to invest in solar PV system.

Factors like shade and roof orientation can affect solar generation. Shade on your roof can reduce the output of your solar array, requiring more solar panels to achieve the same output. It’s the same if your panel doesn’t face north.

So the question that should be always be asked, is what's the maximum number of panels or total KW can I put up on my roof?

There’s no cookie-cutter solution to what kind of solar array your home needs - only the cost effective approach!


What’s the average size of a residential solar system?

A professional will be able to help you with solar array design layout, will be able to get higher quality products and materials at a lower price, and will also be useful in acquiring the government small technology certificate (STC) rebate on your behalf.


There is really no recommended ‘average’ size residential solar array. Only average household energy consumption in a calendar year. In summary, size of solar array is household-specific.

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