Every winter, the same question arrives in our inbox: my solar production has dropped — is something wrong with my system? In almost every case, the answer is no. Winter production in Perth is naturally lower than summer, and understanding why helps you read your monitoring app with confidence rather than concern.
The better news is that Perth enjoys one of the strongest winter solar resources of any Australian capital. Even in June and July, a well-designed system keeps producing meaningful energy — and with the right habits and, ideally, a battery, winter can still be a season of real savings.
At Positive Energy Solutions, we have been designing and installing solar systems in Perth for over a decade. This guide sets realistic winter expectations, explains the physics behind the seasonal dip, and shares practical ways to get more from your system through the cooler months.
How Much Does Solar Production Drop in a Perth Winter?
As a rule of thumb, a Perth solar system produces roughly half as much energy per day in mid winter as it does at the height of summer. Perth averages around 5.5 peak sun hours per day across the year, but that average is made up of long, bright summer days and shorter, more variable winter ones.
For a typical 6.6 kW north-facing system, that means daily production in the mid 30s of kilowatt hours on a clear December day, easing back to somewhere in the mid teens on a clear day in June or July — and less again on heavily overcast days. A 10 kW or 13.2 kW system scales up proportionally, which is one reason larger systems have become the norm: they keep winter production comfortably above household baseload.
If your system is producing in this ballpark, it is behaving normally. The seasonal curve in your monitoring app should look like a smooth wave across the year — high in summer, lower in winter — not a cliff.
Why Winter Production Is Lower
- Shorter days. Perth receives around ten hours of daylight in mid winter versus more than fourteen in mid summer. Fewer daylight hours means a shorter production window.
- Lower sun angle. The winter sun sits lower in the northern sky, so sunlight strikes your panels at a shallower angle and spreads the same energy over a larger area.
- More cloud and rain. Winter fronts bring overcast days that can cut production significantly while they pass. Panels still produce in cloud — typically 10 to 30 per cent of their clear-sky output — but the difference is noticeable.
- Shading returns. That low sun angle can bring neighbouring trees, rooflines and antennas into play in winter even if they cast no shadow in summer.
One factor actually works in winter’s favour: temperature. Solar panels are more efficient when cool. On a crisp, clear July day, panels can briefly produce closer to their rated output than they do on a 40-degree February afternoon, when heat trims their efficiency.
Winter Is When Self-Consumption Matters Most
In summer, most Perth solar homes produce far more than they use and export the surplus. In winter, the equation tightens: production is lower and household usage is often higher, with heating, longer evenings and more time indoors.
That makes self-consumption — using your solar energy directly rather than exporting it — even more valuable in winter. Under the DEBS feed-in tariff, exports earn 10 cents per kilowatt hour during the 3pm to 9pm peak and 2 cents at other times. Energy you use yourself avoids grid purchases at 33.2621 cents per kilowatt hour on Synergy Home Plan A1. Every kilowatt hour you shift into the daylight window is worth roughly 30 cents more than exporting it.
Practical winter habits that make a real difference:
- Run the dishwasher, washing machine and dryer during the middle of the day rather than in the evening.
- Use reverse-cycle air conditioning for heating during daylight hours to warm the home while solar is producing, then let insulation hold the warmth into the evening.
- Schedule heat pump hot water systems and pool pumps to run through the late morning and midday window.
- Charge devices, vacuum robots and e-bikes during the day.
Batteries Earn Their Keep in Winter
A common assumption is that batteries are a summer accessory. In practice, winter evenings are precisely when stored solar is most valuable. Heating loads run long after sunset, and every kilowatt hour your battery supplies during the evening peak displaces grid energy at the day’s most expensive rates — 55.3253 cents per kilowatt hour between 3pm and 9pm for households on Midday Saver.
On clear winter days, most well-sized systems still generate enough surplus to charge a battery meaningfully. On overcast days, households on the Midday Saver tariff have another option: topping up the battery from the grid during the 9am to 3pm super off-peak window at 8.8520 cents per kilowatt hour, then drawing it down through the evening peak. Used this way, a battery saves money even when the sun does not cooperate.
Getting Your System Ready for Winter
- Check your monitoring. A gradual seasonal decline is normal; a sudden step down is not. Positive Energy Protection, powered by Omnidian, flags genuine performance issues automatically and is included with every Positive Energy Solutions installation.
- Let the rain do the cleaning — mostly. Winter rain washes away much of the dust and salt that builds up over a Perth summer. If panels carry stubborn grime or bird droppings, a professional clean restores output safely.
- Watch for new shading. Trees grow. If a section of your array is newly shaded by the low winter sun, it is worth a conversation — sometimes a trim, sometimes a system adjustment.
- Review your tariff. Winter usage patterns differ from summer. If your household has shifted toward daytime flexibility, comparing Home Plan A1 against Midday Saver is worthwhile.
Thinking of Upgrading? Winter Reveals the Truth
Winter is the most honest season for assessing whether your solar system still fits your household. If your panels covered your usage comfortably in summer but winter bills have crept up, that gap is telling you something. Older 5 kW and 6.6 kW systems, sized for the usage patterns and tariffs of a decade ago, often struggle to keep pace with modern all-electric households through winter.
Upgrading to a larger array, adding a battery, or replacing an ageing inverter with a modern hybrid model can transform winter performance. Because winter production is roughly half of summer, extra capacity pays its way in winter first.
Frequently Asked Questions
Do solar panels work on cloudy Perth winter days?
Yes. Panels produce from daylight, not just direct sunshine. Output on a heavily overcast day typically falls to between 10 and 30 per cent of clear-sky production — reduced, but far from zero.
Should I tilt my panels differently for winter?
For almost all residential systems, no. Panels are installed at the roof’s pitch, and the cost of adjustable mounting rarely justifies the modest winter gain. A better investment is simply a slightly larger array, which lifts production in every season.
My inverter shows much lower numbers than summer. Is it faulty?
Almost certainly not. A mid-winter day producing around half of a mid-summer day is textbook behaviour for Perth. The sign of a genuine fault is a sudden drop that does not track the weather — which is exactly what performance monitoring is designed to catch.
Is winter a good time to install solar?
It is one of the best. Installation schedules are typically less congested than the summer rush, and a system installed in winter is fully proven and ready before the high-production months arrive. You also start saving immediately on winter heating loads.
Does a battery still charge fully in winter?
On clear days, a well-sized system will usually charge a correctly sized battery. On overcast days it may partially charge from solar, and households on Midday Saver can top up from the grid at super off-peak rates. We size battery systems with winter, not just summer, in mind.
Make Every Season a Solar Season
Winter does not switch Perth solar off — it simply asks a little more of system design and household habits. Whether you are checking that your current system is performing as it should, considering a battery to carry your evenings, or planning an upgrade sized for real winter loads, we are here to help.
Positive Energy Solutions is a Fronius Solutions Partner Plus, Sungrow Platinum Partner and SigEnergy Gold Installer. Every system we install 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.
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. As Orchestration Lead on Project Symphony — WA’s largest virtual power plant pilot — and Stream Lead on Project Encore, he worked directly with AEMO, Western Power, and Energy Policy WA to shape how distributed energy resources connect and operate on the SWIS. He contributed to the development and rollout of both CSIP-AUS, the inverter communications standard now mandatory under WA’s May 2026 grid rules, and REBAR, the WA Residential Battery Rebate scheme.
His earlier career spanned Synergy, Infinite Energy, and Curtin University’s Sustainability Policy Institute, where he co-authored peer-reviewed research on net zero urban precincts, solar integration, and peer-to-peer energy trading — published in the journal Urban Planning in 2018.
At Positive Energy Solutions, Jason leads sales with a focus on system design accuracy and long-term performance. Positive Energy Solutions designs and installs solar and battery systems, EV chargers and heat pumps, and maintains strong partner accreditations with Fronius, SigEnergy, iStore, and SunPower.
