The 6.6 kilowatt system has been the default size for Australian homes for years. It is the one most people ask about first. Perth has strong, reliable sunshine. A 6.6 kilowatt system is a solid producer here. This guide gives real figures for what it makes across a day and a year. It explains what changes those numbers. Then it makes an honest case for a larger system. For most Perth homes today, a larger system is the smarter choice. This is especially true when a battery is part of the plan.
The short answer is simple. A 6.6 kilowatt system in Perth produces roughly 26 to 30 kilowatt hours on an average day across the year. The longer answer takes more explaining. 6.6 kilowatts is increasingly the old baseline. It is not the right size for a modern home.
What a 6.6kW System Produces in Perth
Perth enjoys around 5.3 peak sun hours a day, averaged across the year. That is among the best of any Australian capital. On that basis, a 6.6 kilowatt system generates around 26 to 30 kilowatt hours on a typical day. Over a year, that is roughly 9,000 to 11,000 kilowatt hours. These daily figures are an annual average. The real number changes with the seasons. On a long, clear summer day, the same system can produce around 35 to 40 kilowatt hours. On a short, overcast winter day, it might make 15 to 20.
That is a genuinely useful amount of energy. The important question is not just how much a system makes. It is how much of it a household actually uses. That is where system size and a battery come in.
What Affects How Much a System Produces
Two identical systems on two different roofs can produce different amounts. Output depends on more than the panel rating.
- Orientation and tilt. The direction the panels face, and their angle, affects how much sun they catch through the day.
- Shading. Trees, buildings or other obstructions that shade the panels reduce output. This matters most at certain times of day.
- Season and weather. Long, clear summer days produce far more than short, cloudy winter ones. This is why annual averages matter more than any single day.
- Panel quality and temperature. Higher-quality panels hold their output better, even in the heat. Real-world production then stays closer to the rated figure.
Why a Larger System Usually Makes More Sense Now
When 6.6 kilowatts became the standard, homes used less power. Feed-in tariffs were generous too. A modest system that exported its surplus paid off. Both of those things have changed. Households now use more electricity. Air conditioning, electric vehicles and all-electric appliances all add to demand. Exported solar in Western Australia now earns only a modest feed-in credit. Larger systems also face export limits. The value today is in generating more and using more of it at home. It is not in exporting.
For that reason, Positive Energy Solutions generally recommends a larger system for most homes. This means at least 8.8 to 9 kilowatts. A larger array produces more energy across the whole day. This includes the morning and afternoon shoulders, when a small system is only trickling. More power is then available to run the home and to charge a battery.
The Battery Factor: Why Size and DC Coupling Go Together
The strongest reason to go larger is storage. Positive Energy Solutions DC-couples a battery on every installation. This connects it on the DC side of a hybrid inverter, so daytime solar charges it directly. The energy stays as DC throughout, avoiding a conversion to AC and back. This avoids conversion losses and makes the whole system significantly more efficient. More of what the panels generate then ends up as usable stored energy.
A DC-coupled battery only delivers its full value when there is enough solar to fill it. This happens after the home’s daytime needs are met. A 6.6 kilowatt system can struggle to do both: run a home through the day, and fully charge a battery. This is hardest in winter. A larger 8.8 to 9 kilowatt array comfortably does both. It powers the home, fills the battery for the evening, and still has headroom on shorter days. Sizing the array and the battery together does this. So does coupling them efficiently. Together, they turn a system from an exporter of low-cost surplus. Instead, it becomes a home that runs on its own energy for most of the day.
System Size and Daily Production in Perth
The table below gives approximate average daily output in Perth for common system sizes. These are annual-average figures. Summer runs higher and winter runs lower.
| System size | Approx. average per day | Suits |
|---|---|---|
| 6.6 kW | Around 26 to 28 kWh | A smaller home with modest usage and no battery |
| 8.8 kW | Around 35 kWh | A typical home, and enough to run the home and charge a battery |
| 9 kW | Around 36 kWh | A typical to larger home with a battery, the common sweet spot |
| 10 kW | Around 40 kWh | A larger, high-consumption home, or one adding an EV |
The right size is not simply the biggest that fits. It is the size that matches a home’s usage, its battery, and Western Australia’s connection rules. A proper design balances all three.
How Positive Energy Solutions Can Help
Positive Energy Solutions sizes each system around a home’s real energy use and its roof. It also considers how the household expects its needs to grow. The battery is then DC-coupled for maximum efficiency. This is how a system is designed to generate plenty. Just as importantly, it is designed to use as much of that energy as possible at home. Every installation is completed by our accredited installers and signed off to Positive Energy’s completion standards. It is backed by a 10-year installation workmanship warranty and Positive Energy Protection, powered by Omnidian. The system is monitored for performance from day one.
Frequently Asked Questions
How much power does a 6.6kW solar system produce per day in Perth?
A 6.6 kilowatt system in Perth produces roughly 26 to 30 kilowatt hours on an average day across the year. Annually, that is around 9,000 to 11,000 kilowatt hours. Output is higher in summer, around 35 to 40 kilowatt hours a day. It is lower in winter, around 15 to 20.
Is a 6.6kW system big enough?
For a smaller home with modest usage and no battery, it can be. Most homes today are different, particularly those with a battery, air conditioning or an electric vehicle. For these homes, Positive Energy Solutions generally recommends a larger system of at least 8.8 to 9 kilowatts. This gives enough generation to run the home and charge a battery.
Why does a battery need a larger solar system?
A battery has to be filled by surplus solar. This happens after the home’s daytime needs are met. A small system can struggle to both power the home and fully charge a battery, especially in winter. A larger array produces enough to do both. This is why system size and storage are best planned together.
Does a bigger system waste power if I do not use it all?
Not when it is paired with a battery and designed for self-consumption. Any surplus goes straight to the battery for the evening. It is stored rather than exported for a low feed-in credit. DC-coupling that battery keeps more of that surplus as usable stored energy.
Get the Right-Sized System for Your Home
A 6.6 kilowatt system is a fine producer. For most Perth homes, though, a larger, battery-ready system delivers far more value. The right size for a particular home, and its battery, is exactly what a Positive Energy Solutions design works out.
Talk to the local team about the right system size for your Perth home: positiveenergy.com.au/contact/
About the Author
Jason Wiktorowicz
Sales Manager, Positive Energy Solutions | Perth, WA
Jason has been at the centre of Western Australia’s energy transition for over a decade. He was Orchestration Lead on Project Symphony, WA’s largest virtual power plant pilot. He was also Stream Lead on Project Encore. In these roles, he worked directly with AEMO, Western Power and Energy Policy WA. Together they shaped how distributed energy resources connect and operate on the SWIS. That work included developing and rolling out CSIP-AUS, now mandatory for all new WA grid connections. He also led Emergency Solar Management, the first program of its kind in WA. He led VPP for Schools too, which provided direct market benefits through Supplementary Reserve Capacity. He also led REBAR, the WA Residential Battery Rebate scheme.
At Positive Energy Solutions, Jason leads sales with a focus on system design accuracy and long-term performance. Positive Energy Solutions installs solar and battery systems, EV chargers and heat pumps. It also holds partner accreditations with Fronius, SigEnergy, iStore and SunPower.
10-year installation workmanship warranty. Positive Energy Protection, powered by Omnidian, performance monitoring included on all systems.
