What Size Solar System Do I Need?

What size solar system do I need?

What Size Solar System Do I Need? 

Installing solar is not only a wise move for our clean energy future, it’s a highly effective way to lower your energy bills. Yet understanding which solar system size makes sense for your needs might be more complicated than expected. After all, everyone’s home is different, just like their power usage demands.

With numerous factors big and small impacting your decision, knowing how to weigh these up is critical to finding the right-sized solar system. Here, we explore the various considerations, highlighting how features from your roof size to the appliances in your kitchen affect your needs and ultimately guide your decision.

Factors Affecting Your Solar System Size

Finding the ideal solar system size is crucial. While an oversized system might future-proof your energy needs, justifying the extra cost doesn’t always add up. If your hybrid system is too small, you might rely on the grid more than you’d like. Or, if you have an off-grid solar system, you might find yourself in the dark. Here are the major factors to consider when researching which size solar system is right for you.

Power usage

You can’t find the ideal solar system size if you don’t have a solid grasp of your current power usage. While it’s not the most exciting activity, looking through your recent electricity bills is the best place to start. While checking your usage for a single month can point you in the right direction, reviewing how your usage changes across seasons is far more helpful.

Once you’ve gathered enough bills, calculate your average daily usage, measured in kilowatt-hours (kWh). While the average Australian home is estimated to use 18 kWh per day, the amount you use could be more or less. Consider factors like the number of people living in the house, the size of your home, how often you use heating and cooling and how much time you spend at home.

Battery storage

Battery storage is important to consider when choosing a solar system. As most energy providers no longer offer attractive feed-in tariffs, storing excess energy in dedicated batteries makes sense. Remember, a typical home uses more energy in the morning and evening. But as peak solar production occurs around midday, you might not fully benefit from the power generated unless you install solar batteries.

However, not everyone has the budget for battery storage with their home solar system. While the price is coming down, this innovative technology remains costly. Instead, some people choose to install a larger solar system without the added cost of batteries. With a solid understanding of your consumption habits, deciding whether solar battery storage is worth the extra investment is possible.

Roof size and orientation

The size of the solar system you can install depends on the surface area of your roof available. Although many homes have more than enough space for solar panels, others with steep pitches or thick overhanging trees might only have a limited area to use. Some roofing materials like wood and slate can also make installation more challenging.

The orientation of your roof is another critical factor. With north-facing roofs receiving the most sunlight throughout the day, structures facing more towards the south will generate less energy in comparison. While this doesn’t mean solar panels are worthless, your roof size, orientation and tilt angle will make a tangible difference to the energy you produce.

Time of day usage

A clear picture of your average energy consumption is fundamental to choosing a solar system size. However, it’s almost equally important to understand when your energy requirements are highest. In a typical household, this is the morning and evening when people are home from work. Yet those with differing schedules, like remote workers or retirees, might use more energy at alternative times of the day.

Although solar batteries improve how you benefit from the energy your system generates, maximising “self-consumption” is an efficient approach. This means installing a suitably sized system that captures enough energy to power your devices when you’re at home. If you don’t expect to invest in solar batteries in the coming years, installing a smaller system that suits your current habits could be a wiser choice.


You can’t overlook seasonal changes when choosing a solar system. As the sunlight reaching your solar panels can shift throughout the year, the darker months could mean your home doesn’t generate enough energy to sustain your needs. Fortunately, those based in New South Wales benefit from approximately 4-5 peak sun hours in summer and 3-4 hours in winter. 

While peak sun hours are just one part of the equation, knowing that your home receives enough sunlight to generate sufficient energy is a good starting point. It’s also wise to explore how factors like solar panel type, inverter efficiency, roof tilt and orientation help determine the most appropriate solar system size for your needs.

Future usage

Your daily energy requirements could be relatively consistent, but they might not stay this way forever. When researching the solar system size you need, adopt a forward-thinking approach to help reach the right decision. For example, your teenage kids might fly the nest soon or you might finally embark on a long-awaited house extension.

Yet the changes don’t have to be so dramatic. Perhaps you want to expand your air conditioning system or add a spa in the backyard. Australians are also increasingly turning towards electric vehicles, with the ability to charge using solar at home an enormous benefit. Planning for future electricity usage is essential for finding the right solar system size.

Network limitations

Even though feed-in tariffs have reduced over time, this option still represents value for homes generating excess power. However, certain network limitations can prevent you from gaining access to this benefit. Why? Since the electricity grid was not designed for bidirectional flow, network overload can occasionally become an issue.

With this in mind, distribution network service providers (DNSPs) limit the size of solar systems allowed. In some cases, a larger solar system size can make you ineligible for feed-in tariffs or require additional approvals that cost extra time and money. Before you decide, get to know your network limitations alongside any approval criteria.

How to calculate the size of your solar system

There’s no shortage of factors to consider when asking yourself: “What sized solar system do I need?” However, you can calculate a general estimate by dividing your average daily electricity usage by 3.5. 

As the most electricity generated daily by 1 kW of solar panels in Australia is between 3.5 kWh and 5 kWh, this simple equation provides a helpful benchmark.

For example, if your current daily electricity usage is 15 kWh, an appropriate solar system size could be 4.3 kW. View our pricing table and solar system size calculator below to learn more about your options.

Solar system size calculator

If you've got a copy of your latest power bill handy, head to our online calculator to work out what sized system you need. You can enter in all the appliances at your place and it can design the right sized solar system you need.

Go renewable with Rainbow Power Company

Ready to add a solar system to your home? Rainbow Power Company has led Australia’s solar revolution since 1987. Get in touch with our friendly team to learn more about our off-grid and hybrid solutions for households and commercial operations.

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