Key points
- A north-facing 6.6kW solar system produces about 25–28 kWh a day in Adelaide and 22–24 kWh a day in Melbourne, averaged across the year.
- That’s roughly 9,000–10,000 kWh a year in Adelaide and 8,000–8,900 kWh a year in Melbourne.
- Winter output is about half of summer: around 17–19 kWh a day in an Adelaide winter versus 31–35 kWh in summer. Melbourne drops to about 14–16 kWh a day in winter.
- East–west roofs produce about 12–14% less over a year than north-facing roofs, but spread generation across the day.
How much does a 6.6kW solar system produce? In Adelaide, a well-installed, north-facing 6.6kW system averages about 25 to 28 kWh a day across the year, and in Melbourne about 22 to 24 kWh a day. Output swings with the seasons, from over 30 kWh a day in summer to under 20 kWh in winter. Below we break down 6.6kW solar system output by season and by month for both cities, explain what reduces it, and show how to check your own system is performing.
How much power does a 6.6kW solar system produce per day?
Two independent methods give very similar answers:
- Clean Energy Council guideline figures put average output at about 4.2 kWh per installed kW per day in Adelaide and 3.6 kWh in Melbourne. For 6.6kW, that’s about 27.7 kWh and 23.8 kWh a day.
- PVGIS modelling (the European Commission’s free solar calculator), set up for a 22° north-facing roof with 14% system losses, gives 27.5 kWh a day in Adelaide and 24.4 kWh in Melbourne.
Real systems vary with roof angle, temperature, dust and equipment, so a fair expectation is a range: about 25–28 kWh a day in Adelaide and 22–24 kWh a day in Melbourne for a north-facing system with little shade. This article is part of our complete guide to home solar panels.
6.6kW solar system output by season
Australia’s seasons make a big difference. Summer days are long and the sun is high. In winter, Adelaide and Melbourne get shorter days, a lower sun angle and more cloud, especially in Melbourne.
| Season (north-facing 6.6kW) | Adelaide, kWh per day | Melbourne, kWh per day |
|---|---|---|
| Summer (Dec–Feb) | 31–35 | 29–33 |
| Autumn (Mar–May) | 22–25 | 19–21 |
| Winter (Jun–Aug) | 17–19 | 14–16 |
| Spring (Sep–Nov) | 28–32 | 25–28 |
| Annual average | 25–28 | 22–24 |
| Annual total | 9,000–10,000 kWh | 8,000–8,900 kWh |
Ranges are based on PVGIS modelled output, with the lower end allowing for typical real-world losses such as dirt, heat and minor shading. The gap between the cities is widest in winter: Melbourne’s June output is roughly 75–80% of Adelaide’s.
Month-by-month estimates for Adelaide and Melbourne
These are modelled averages per day for a north-facing 6.6kW system. Any single day can be well above or below, depending on cloud.
| Month | Adelaide (kWh/day) | Melbourne (kWh/day) |
|---|---|---|
| January | 35.1 | 33.5 |
| February | 33.8 | 31.2 |
| March | 29.8 | 26.7 |
| April | 24.6 | 20.7 |
| May | 19.5 | 15.6 |
| June | 17.4 | 13.4 |
| July | 18.1 | 15.3 |
| August | 22.1 | 19.1 |
| September | 28.0 | 24.6 |
| October | 32.4 | 29.2 |
| November | 34.2 | 31.0 |
| December | 34.6 | 32.9 |
The practical takeaway: plan your daytime loads and any battery around winter output, not summer. A 6.6kW system that covers your daytime use comfortably in January may leave you buying more grid power in June.
Why most 6.6kW systems use a 5kW inverter
Nearly every 6.6kW package pairs 6.6kW of panels with a 5 kW inverter. Industry design rules allow panel capacity of up to 133% of the inverter rating, and 6.6kW is exactly that for 5 kW. It’s a cost-effective combination, and a 5 kW inverter also fits easily within network limits on single-phase homes.
Does the smaller inverter waste power? A little. Panels rarely produce their full rated output because heat and sun angle reduce it, so the inverter only “clips” the peak on the best summer middays. The loss is usually small over a year and is outweighed by the extra morning, afternoon and winter generation from the larger array. You can see how this is put together in our 6.6kW solar system package.
What reduces a 6.6kW system’s output?
Roof direction and tilt
North-facing panels produce the most energy over a year. In our PVGIS modelling, a 6.6kW system split east–west at a 15° tilt produced about 8,800 kWh a year in Adelaide (around 24 kWh a day) and about 7,700 kWh in Melbourne (around 21 kWh a day). That’s about 12–14% less than north-facing, but output starts earlier and finishes later, which can suit households with morning and late-afternoon loads. See how roof orientation and shade affect solar panels.
Shade
Even partial shade from a tree, flue or neighbouring house can cut a string of panels’ output noticeably. Optimisers or microinverters can reduce the impact on difficult roofs.
Heat
Panels lose efficiency as they heat up. On a 40°C Adelaide day, panel output can be well below its rating, which is one reason summer output doesn’t rise as much as day length would suggest.
Dirt and ageing
Dust, bird droppings and pollen reduce output, particularly on low-tilt roofs that don’t self-clean in the rain. Panels also degrade slowly over time. Most current panel warranties guarantee output stays above roughly 85–90% of the original after 25–30 years.
How to check your 6.6kW system is performing
Most inverters come with a monitoring app that shows daily generation. To judge whether your system is on track:
- Compare the same month year to year, not one day against another.
- Use the monthly table above as a rough benchmark, adjusted for your roof direction.
- Look for sudden drops on clear days, which can point to a tripped isolator, inverter fault or new shade.
- If output is consistently more than 15–20% below expectations for your orientation, ask your installer to check it.
Our guide to monitoring your solar system explains what to look for in the app and which faults are most common.
How much of that power will you actually use?
Generation is only half the story. Most households use about 30–40% of their solar directly, and export the rest. For a 6.6kW system in Adelaide, that’s roughly 8–11 kWh a day used in the home. Every kilowatt-hour you use saves the full retail price, while exports now earn only a few cents in both SA and Victoria.
Shifting loads into daylight hours lifts that share. Timers on hot water, dishwashers and pool pumps, and charging an EV at midday, all help. Our list of ways to use more of your own solar power has practical ideas.
If your household already uses more than 25 kWh a day, or you’re planning an EV or battery, a 6.6kW system may be undersized. Read what size solar system you need or compare 10kW solar output and payback.
Tip: Ask your installer for a generation estimate specific to your roof (direction, tilt and shading). It should be in the same ballpark as the figures above; if it’s much higher, ask how they calculated it.
Frequently asked questions
How many kWh does a 6.6kW solar system produce per day?
On average, about 25 to 28 kWh a day in Adelaide and 22 to 24 kWh a day in Melbourne for a north-facing system with little shade. Summer days can produce 31 to 35 kWh, while winter days often produce 14 to 19 kWh depending on the city and the weather.
How much does a 6.6kW solar system produce in winter?
In June and July, a north-facing 6.6kW system averages roughly 17 to 18 kWh a day in Adelaide and 13 to 15 kWh a day in Melbourne. Cloudy days can be much lower. East–west systems produce less again in winter because the sun sits low in the northern sky.
Is a 6.6kW solar system enough to run a house?
It can cover most daytime use for a typical household, but not overnight use without a battery. A 6.6kW system usually suits homes using up to about 20 to 25 kWh a day. Larger, all-electric or EV-owning households often benefit from a 10kW or 13kW system.
Why is my 6.6kW system never showing 6.6kW?
That’s normal. Panel ratings are measured in laboratory conditions, and real-world heat, sun angle and wiring losses reduce output. Most 6.6kW systems also use a 5 kW inverter, so the AC output peaks at around 5 kW on the best days. Check daily kWh totals rather than peak power.
Want an output estimate for your own roof? Our team designs and installs 6.6kW systems across Adelaide and Melbourne, with shading and orientation checked on site. Get a free quote and we’ll model the expected generation for your home.
Sources: European Commission JRC – PVGIS photovoltaic performance tool (modelled October 2026; Adelaide −34.93, 138.60 and Melbourne −37.81, 144.96; 22° north-facing and 15° east–west; 14% system losses); Clean Energy Council – Consumer guides (accessed October 2026); energy.gov.au – Solar PV and batteries (accessed October 2026). Output figures are modelled estimates; actual generation depends on your roof, equipment and weather. Featured image: Orderinchaos / Wikimedia Commons, CC BY-SA 3.0.
