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How Much Rooftop Solar Power Can You Install? – A State by State Guide

There are limits to the size of the solar panel system you can install on your rooftop. Naturally, there is only so much weight your roof can support! But a less obvious limit sets how much energy your rooftop solar power panels system is permitted to generate.

Rooftop solar power panels: how many can you install? Solar domestic power increasingly popular.A large increase in rooftop solar installation reduces power bills for Australian consumers. Image: Pixabay

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This figure varies. Your electricity retailer imposes restrictions on solar power capacity depending on where you live, sometimes even which town you live in!

These two factors, the number of solar panels and their power output are also subject to how many solar installers or how much clean energy you want to generate for home or business use.

Let’s look at the factors involved in limiting your solar power while exploring the levels of energy you can achieve in your area.

Energy Matters has been a leader in the renewable energy industry since 2005 and has helped over 40,000 Australian households in their journey to energy independence. 

Let us discuss and choose the best quote that suits your needs and budget, and we can connect you with our trusted local installers, who will provide up to 3 FREE quotes for your home and business solar energy system. Get your free quotes today!

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Why does the electricity retailer set limits?

Technically, it’s not your retailer setting the limits on how much solar energy or many rooftop solar power panels you can install. The limits are actually decided by the owners of the network that distributes the electricity, the poles and wires. This network owner is also known as the distributor. Confusingly, in some cases your energy retailer also owns the network too. Energex in Queensland, for example.

Electricity transmission towers are owned by the distributor
Electricity transmission towers

Limits on your solar generating capacity are set by companies like Energex because the electricity distribution network was originally set up to push power in one direction only and at a predictable rate. When wind and solar power came along there was a disruption in this traditional network model. The consumers became producers, and they wanted to feed their energy into the network.

This two-way model of energy distribution is a people’s revolution in energy. It’s great for the environment and great for the hip pocket.

Impact of solar on the grid

But the owners of the networks are concerned that too much solar electricity flowing into the grid could disrupt the operation of the existing power stations. For example, the grid needs to be kept at a certain voltage. Too much solar input pushes the voltage up and creates problems.

What’s needed is smarter technology that regulates the influx of clean energy so that it can co-exist with the older types battery systems of generators. That technology is not quite at the stage where solar power can feed to the grid without limit. But it’s only a question of time until the regulators work out a way to tap into the excess electricity of every rooftop solar system. Already, neighbours are sharing electricity in some areas, cutting out the energy retailer completely.

What are the current limits for solar installation?

Unless otherwise specified, states and territories give automatic approval to rooftop solar power panels systems that comply with the Australian standard for solar installation: 5 kW or under. In most states and territories, there is automatic approval given to any other solar power system up to 5 kW. However, this is in not set in stone.

For example, in May 2017, the Queensland Government (which owns retailer Energex) changed the regulations for solar installation limits. Automatic approval for rooftop solar used to stop at 5 kW, but the new rules give approval for up to 10 kW.

Battery proviso

The proviso is that you are not permitted to have a battery system capable of feeding power into the grid. The government was fearful of a blowout in their feed-in tariff budget, which originally did not allow for batteries. Feeding power into the grid from batteries during the night would prove too costly for its feed-in tariff scheme.

The AS/NSZ 4777 standard allows most networks to allow system sizes on a single phase connection up to 5 kW. Three phase connection size is up to 30 kW.

As long as your rooftop solar power panels system meets the requirements of your network, you will have no problem getting pre-approval.

But you should speak with your solar installer about what you can and can’t do. For example, in Western Australia, some electricity retailers allow the installation of rooftop solar depending on which town you live in and provide a handy calculator.

You may also want to take into account size dependent rebates. Currently Solar Victoria is offering rebates through the Solar Homes program for those in Melbourne and the rest of the state who wish to buy solar panels. The Victorian Government is providing a significant rebate, up to the value of half of an average 4kW solar panel system so it makes sense to get a system bigger than 4kW.

State by state comparison

The following table shows the limits for automatic pre-approval for solar panel systems by state/territory and energy retailer. The figures quoted are inverter limits.



Single phase: 5 kW



Single phase: 10 kW
3-phase: 30 kW


Single phase: 5 kW (3 kW rural)
3-phase: 15 kW (9kW rural)


Single phase: 5 kW
3-phase: 30 kW



Class 1 – Private/residential:
Single phase: 5 kW
3 phase: 7 kW (10 kW per phase inverter limit)

Class 2 – Private/residential & small commercial:
3 Phase: 30 kW with zero export limiter inverter (10 kW per phase inverter limit)



Up to 30 kW, however all solar installations are subject to the application process Ergon

Single phase: 5 kW
3-phase: 15 kW


Single phase: 5 kW
3-phase: 30 kW


Tas Networks

Single phase: 5 kW
3-phase: 30 kW


United Energy

Single phase: 10 kW
3-phase: 30 kW


Single phase: 5 kW
3-phase: 30 kW


Single phase: 10 kW
3-phase: 30 kW


Single phase: 5 kW
3-phase: 15 kW


Western Power

Single phase: 5 kW
3-phase: 30 kW

Horizon Power

Eligibility to install rooftop solar depends on which town you live in – use a calculator.

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Feed-in tariffs, state by state

There are rebate schemes to encourage solar users to feed electricity into the grid from their rooftop solar power panels. You can find out about them on Energy Matters’ feed-in tariff page.

Otherwise, here are the contact numbers to find out about the latest feed-in tariffs in your area:

  • ACT: Environment, Planning and Sustainable Development Directorate, 13 22 81
  • NSW: Division of Resources and Energy, 1300 736 122
  • NT: Department of the Chief Minister, (08) 8999 5511
  • QLD: Department of Energy and Water Supply, 13 43 87
  • SA: Department of State Development, (08) 8226 5500
  • TAS: Department of State Growth, 1300 135 513
  • VIC: Department of Environment, Land, Water and Planning, 136 186
  • WA: Public Utilities Office (08) 6551 1000

Rooftop solar power panels system sizing

As mentioned previously, up to 5 kW seems to be the current acceptable capacity for solar dictated by most electricity retailers.

Regardless of that limit, to get the very most out of your rooftop solar power panels you should consider having the system linked to a battery. That’s because most of a typical family’s energy consumption occurs after work and school hours.

So, during the day while your panels are busily making electricity, that electricity is going into the grid at a feed-in tariff that is usually a lot less than the retail price you will pay when you really need the energy. It’s more effective to charge your home battery with any unused electricity. Note that batteries raise significantly the investment that you need to make initially and will increase the time it takes for your system to pay for itself.

Size matters but so does value and a battery can add to your payback time

One of the best ways to gauge the size of the solar system you need is to review your power usage on your electricity bill. According to the Clean Energy Council, a typical Australian house consumes around 18 kilowatt hours (kWh) per day. So a 1-2 kW solar system displaces an average of 25-40% of the average electricity bill.

Consider that today’s average size for a solar system is 3 kWh. It’s possible in some cases to virtually eliminate power bills with the right solar system, battery storage and smart inverter.

How much sunlight is available?

The Clean Energy Council table below shows how much energy you can expect to generate from the sun using rooftop solar power panels in Australia’s capital cities.

The power output of a solar PV system depends on its efficiency, size and location. The table below shows the average daily production of some common grid-connected systems throughout Australia.

City 1 kW system 1.5 kW system 2.0 kW system 3.0 kW system 4.0 kW system
Adelaide 4.2 kWh 6.3 kWh 8.4 kWh 12.6 kWh 16.8 kWh
Alice Springs 5.0 kWh 7.5 kWh 10.0 kWh 15.0 kWh 20.0 kWh
Brisbane 4.2 kWh 6.3 kWh 8.4 kWh 12.6 kWh 16.8 kWh
Cairns 4.2 kWh 6.3 kWh 8.4 kWh 12.6 kWh 16.8 kWh
Canberra 4.3 kWh 6.45 kWh 8.6 kWh 12.9 kWh 17.2 kWh
Darwin 4.4 kWh 6.6 kWh 8.8 kWh 13.2 kWh 17.6 kWh
Hobart 3.5 kWh 5.25 kWh 7.0 kWh 10.5 kWh 14.0 kWh
Melbourne 3.6 kWh 5.4 kWh 7.2 kWh 10.8 kWh 14.4 kWh
Perth 4.4 kWh 6.6 kWh 8.8 kWh 13.2 kWh 17.6 kWh
Sydney 3.9 kWh 5.85 kWh 7.8 kWh 11.7 kWh 15.6 kWh

The rated output, e.g. 4.0kW, is that achieved in perfect lab conditions. The table above takes real wold conditions into account when predicting averages for any given system.

Panels generate more electricity in summer than in winter. The table above reflects the electricity generated averaged across the whole year.

A typical Australian house consumes around 18 kilowatt hours (kWh) of electricty per day. This means that a 1-2 kW system could displace 25-40 per cent of your average electricity bill.

City solar comparison

It shows that in Brisbane a 3 kW solar system will on average generate 12.6 kWh daily, or 70% of an average household’s daily power usage.

In Melbourne, a city that is on average less sunny than Brisbane, the same 3 kW solar system would generate 10.8 kWh daily (60% of daily usage).

This shows that with batteries to store the excess solar power you generate, it is possible to supply a substantial amount of your home energy needs. As long as the correct sized system solar battery was installed.

Other questions you could ask about your solar system include:

  • Does the limit laid down by your electricity retailer apply only to solar inverter capacity, or also battery inverter capacity?
  • Are you limited on how much electricity you can feed into the grid from your panels?
  • Will you need a solar smoothing device? These iron out the fluctuating energy output of your panels as a result of changes in the weather.

Get in touch with Energy Matters now

The best way to find out the ins and outs of rooftop solar power panels installation is to get in touch with Energy Matters in your area and talk to one of our consultants about a quote. It can seem more complicated than it really is.

They will be able to tell you about the latest rules and limits on your solar installation. Inside information from Energy Matters’ experts will make sure your system is the best you can afford, while remaining within the regulatory framework to your electricity retailer.

Now is the right time to switch to Brisbane solar energy. We recommend seeking at least 3 solar quotes to ensure that you are getting the best deal and selecting the right solar installer in Brisbane whom you can trust. With this, you can guarantee a solar system in Brisbane that meets your energy needs.

Factors affecting the number of solar panels you can install on your roof

When considering installing solar panels, it is essential to understand the factors that can affect the number of solar panels installed you can install on your roof. Factors such as roof size, orientation, shading, and others play a significant role in determining the maximum solar capacity you can achieve.

Roof size: The size of your roof directly influences the number of solar panels you can install, with a larger, unobstructed, flat roof often enabling higher energy generation, while smaller roofs can still support a system that meets a portion of your electricity needs.

Roof orientation: The ideal orientation for solar panels in Australia is a north-facing roof, as it maximises exposure to sunlight throughout the day and results in optimal energy generation, while east and west-facing roofs can also be considered but may produce slightly less energy, and south-facing roofs are generally less suitable due to reduced sunlight exposure.

Roof angle: The efficiency of solar panels is influenced by the roof pitch, with an optimal angle in Australia being approximately equal to the latitude of the location, such as 33 degrees in Sydney, although a range of roof angles can still generate a considerable amount of energy.

Shading: Shading plays a crucial role in solar panel efficiency. It obstructs sunlight and diminishes energy production, necessitating a thorough evaluation of shading conditions on the roof and expert advice to determine possible solutions or alternative solar panel capacity and placements.

Energy consumption: To determine the appropriate number of solar panels needed for your household, it is important to evaluate your energy consumption patterns, as higher energy usage typically requires a much larger solar system size to meet electricity needs effectively.

Local regulations and incentives: Local regulations and incentives play a significant role in determining the number of solar panels allowed and the financial feasibility of installation, emphasising the importance of understanding these factors before making any decisions.

Calculating the optimal number of solar panels for your roof

Investing in solar energy is beneficial for homeowners in Australia due to abundant sunlight. Determining the ideal number of solar panels for a roof can be complex but essential. Factors such as roof size, orientation, tilt, shading, and energy consumption patterns must be considered. Calculations involve determining average daily energy consumption and available roof space and using formulas to estimate the number of panels. Online tools and more solar energy professionals can assist in this process. Solar panel wattage, average daily peak sunlight hours, and system efficiency are factors in the calculation formula. Consulting with experts is recommended for personalised advice. Careful consideration and calculations ensure an optimal solar investment that maximises energy generation and cost savings.

Still can’t afford to switch to solar power?

Are you considering getting solar panels but are currently short on funds? You can still invest wisely, and Energy Matters can help you. 

Powow and Energy Matters have teamed up to provide consumers with an alternative to switching to solar power and battery storage. 

The biggest obstacle to installing solar and battery storage is typically finance. With Powow’s PPA and VPP, our customers will have a $0 upfront option and financial stability in the uncertain energy market.

Get up to 3 obligation-free quotes by getting in touch with us right away. Find out what payment plan options suit your needs and budget!

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