3kW Solar System: Too Small for the Average Home?

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Less than 10 years ago a 3kW solar system used to be a pretty standard size for a residential installation – but those days are behind us. In 2022, the average Australian household typically installs at least a 6kW solar PV system to cover its energy needs, with many opting for even larger systems. If you’re thinking of going solar and have a limited budget, you may be tempted to install a smaller system such as a 3kW. However, it’s important to keep in mind that a smaller system will likely mean higher electricity bills in the long run. Below we outline some key information about 3kW systems to help you make an informed decision about whether or not this size system is right for you.

how many solar panels for 3kw system

Why are 3kW solar systems less popular in 2022?

Considering 3kW systems used to be the norm back in 2012, you’re probably wondering what’s changed? Why has the average system size more than doubled in a decade?

A key reason is the cost of solar panels and associated equipment has fallen significantly over the past decade, making it more affordable for households to install larger systems that actually cover their energy needs. In fact, 6kW systems can now be purchased for around the same price as a 1.5kW in 2010.

Panel efficiency has also increased, meaning that you don’t need as much roof space to generate the same amount of electricity. The average panel conversion efficiency has increased from 15% to well over 20% owing to the many improvements in photovoltaic technology. As a result of these advancements in efficiency, the power rating of a typical size panel has increased from 250W to 370W. Some extremely efficient panels can even generate up to 415W.

Several additional factors are also driving the general trend for bigger systems, including the uptake of battery storageelectric vehicles and a push towards greater energy independence from the grid. It’s also a reflection of changing consumer attitudes and behaviours when it comes to solar PV. Australians are becoming more comfortable with the idea of generating, storing and using their own energy.

The output of a 3kW solar system

The output of a 3kW solar system will vary depending on the time of year and location, but a good rule of thumb is that you can expect a 3kW system to generate around 12-14 kWh per day, on average.

Different locations across Australia will experience different average daily solar insolation (the amount of sunlight that hits the ground), which in turn will affect the output of your system. For example, a 3kW system in Sydney will produce, on average, 11.7kWh per day while in Perth it will generate nearly 13.2kWh per day.

Keep in mind that this output is only generated during daylight hours, meaning you won’t be able to rely on your solar PV system to cover any of your energy needs at night unless you have batteries installed.

How many panels and how much roof space do I need for a 3kW solar system?

Standard solar panels are typically around 330 to 400W and 1m x 1.7m in size, so a 3kW solar system will require approximately 7-10 solar panels and 12-17m2 of roof space.

How much does a 3kW solar system cost?

The current average price for a fully installed 3kW solar system in Brisbane is around $4,000 which includes the STC rebate and GST. 

Reasons to install a 3kW solar system

You have very limited roof space: If your roof is very small, a solar installer in Brisbane may advise that a larger system isn’t possible or practical. In this case, a smaller system such as a 3kW system may have to suffice.

You have a small home with few occupants: A 3kW solar system should be able to run most appliances found in a small one-bath, two-bedroom home with less than three occupants.

You have low day-time energy consumption: If your home has very low daytime energy usage, you may find that a smaller system can cover your needs. Newer homes built with high energy-efficiency ratings that use energy-efficient lighting and appliances should theoretically use less electricity.

Is a 3kW solar system too small?

Considering the average Australian household uses 16-20kWh of electricity per day, a 3kW system will probably be too small to cover the current and future needs of most families.

Of course, every home is different and your electricity usage will vary depending on a range of factors – that’s why it’s important to have a professional solar installer assess your specific needs before making any final decisions.

What size solar system do I need?

The minimum solar system size you’ll need to cover your energy usage will depend on a number of factors, including the number of occupants in your household, the average daily electricity consumption, the climate zone you live in and whether you have any battery storage or an electric vehicle.

A key consideration of sizing should be about maximising value – and maximising the value you get out of your system is largely about solar self-consumption. If you want to oversize your system simply because you want to make a return from the energy you send back to the grid, it isn’t going to be worth your while. Feed-in tariffs simply aren’t what they used to be.

Ideally, you will want to size your system to allow for your current and expected future energy consumption.

Modern solar panels last quite a long time – around 25-30 years – so if you think your energy needs are likely to change in this time (you’re getting a pool or an electric vehicle for example), it’s worth considering an oversized system that can accommodate these energy-intensive features.

Another very important consideration is battery storage. An increasing percentage of Australians are opting to add a battery when purchasing a solar system. In fact, in Sydney last year, 27% of new systems were installed with a battery.

Batteries allow you to store the excess solar energy your system produces during the daytime for use at night or during blackouts, and can significantly reduce your reliance on the grid. The larger your system capacity, the more self-generated electricity you’ll have available to store and use to power your home or charge your EV at night.

To get a better idea of the minimum system size you’ll need, we recommend using Energy Matters’ free online solar and battery storage calculator. All you need is your postcode and your average daily energy consumption(kWh) and the calculator will give you an indication of the minimum system size and recommended battery storage for your home.

You can usually find your average daily energy consumption(kWh) on a recent electricity bill.

As a final word of advice, we recommend getting multiple quotes from different solar retailers and installers to ensure you’re getting the best deal on your new system. Shopping around is the best way to make sure you’re getting value for money.

Energy Matters can assist by providing you with up to three obligation-free quotes from our network of accredited solar installers. It’s free, quick and easy – get started here.