How rooftop solar works

A rooftop solar system has three main jobs, and they happen automatically every time the sun is shining:

1. Solar panels contain photovoltaic cells that convert sunlight into direct current (DC) electricity. More sunlight means more DC output, but the panels produce some power even on overcast days.
2. The inverter converts that DC electricity into alternating current (AC) at 230 volts, which is the type of electricity your home appliances use. The inverter is the “brain” of the system, monitoring output, grid voltage, and safety.
3. Your switchboard receives the AC electricity and distributes it to whatever is drawing power. If your panels are producing 3 kW and your house is using 2 kW, the extra 1 kW flows out through your meter to the grid.

Solar systems in Australia are described by two numbers that are often confused:

The most common residential system in Australia today is 6.6 kW of panels on a 5 kW inverter. Larger homes with higher daytime consumption, batteries, or EVs are increasingly opting for 10–13 kW systems with 8–10 kW inverters.

* Approximate annual average for Sydney. Output varies by location, orientation, and weather. Northern cities produce more year-round; southern cities have bigger seasonal swings.

Your system’s nameplate rating (e.g. 6.6 kW) is its theoretical maximum under perfect lab conditions. Real-world output depends on several factors:

• Orientation — North-facing panels produce the most energy across the year in Australia. West-facing panels produce more in the afternoon (useful if you want to cover the early evening peak). East-facing panels produce more in the morning.
• Tilt angle — Panels tilted at roughly your latitude angle (20–35 degrees for most of Australia) capture the most annual energy. Flat roofs produce less per panel but can fit more panels.
• Shading — Even partial shade on one panel can significantly reduce output for the whole string. Trees, chimneys, neighbouring buildings, and antenna masts are common culprits. Micro-inverters or optimisers can reduce shading losses.
• Temperature — Solar panels lose efficiency as they get hotter. A 40-degree day in Adelaide means your panels might produce 10–15% less than the same sunny day at 25 degrees.
• Time of year — Summer days are longer and the sun is higher, producing significantly more energy. A 6.6 kW system in Melbourne might produce 35 kWh on a clear January day and 12 kWh on a short, cloudy June day.
• Dust and dirt — A thin layer of dust, pollen, or bird droppings can reduce output by 5–10%. Rain usually provides adequate cleaning, but panels at a shallow tilt may need occasional hosing.

The Clean Energy Council (CEC) is Australia’s peak body for the renewable energy industry. For solar installations, CEC accreditation matters in two ways:

• Accredited installers — To claim Small-scale Technology Certificates (STCs, the “solar rebate” that reduces your upfront cost), the system must be designed and installed by a CEC-accredited installer. Using a non-accredited installer means you miss out on the discount, which can be worth $2,000–$4,000 depending on system size and location.
• Approved products — Both the panels and inverter must be on the CEC’s approved product list. This means they’ve been tested to Australian standards for safety, performance, and durability.

Once you have solar, the next question is how to get the most value from it. Exporting surplus electricity earns you a feed-in tariff, but using that electricity yourself is worth far more.