Local · 10 November 2026 · 5 min read
Solar in Ballarat: cold clear days and short winter ones
What the Bureau of Meteorology's records say about sun in Ballarat, why cold clear days suit solar panels, and how to size a system and battery for winter.
Ballarat has a name for being cold, and people sometimes take that to mean it is a poor place for solar. The long-term records say otherwise. Here is what the Bureau of Meteorology has measured at Ballarat, why cold weather is actually kind to solar panels, and what the city's climate means when you size a system and a battery.
What the Bureau's records show
The Bureau of Meteorology has recorded daily solar exposure at Ballarat Aerodrome since 1990. Solar exposure is the total energy from the sun landing on a flat square metre over a whole day, measured in megajoules (MJ). The long-term averages for Ballarat are:
- Summer: 25.4 MJ a day in January and 25.1 in December
- Autumn: 17.3 in March, falling to 11.6 in April and 8.0 in May
- Winter: 6.2 in June, the lowest of the year, and 6.9 in July
- Spring: 13.9 in September and 18.4 in October
- Year round: an average of 15.6 MJ a day
For comparison, the Bureau's figure for Melbourne Airport is 15.0 MJ a day across the year. Measured this way, Ballarat collects slightly more sunlight over a year than Melbourne Airport, not less.
To turn these numbers into something more familiar, divide by 3.6 to get kilowatt hours per square metre. June's 6.2 MJ is about 1.7 kWh, and January's 25.4 MJ is about 7.1 kWh. So a typical day in midwinter delivers roughly a quarter of the sunlight of a typical day in midsummer. That is the real story for solar in Ballarat. It is not the cold that matters, it is the short, low winter days.
Why cold, clear days help
Every solar panel is rated at a cell temperature of 25 °C. When the cells get hotter than that they make a little less power, and when they are cooler they make a little more. The datasheet calls this the temperature coefficient.
Two of the panels we install show how small that number is. The Jinko Tiger Neo III all black panel lists a temperature coefficient of -0.26% per °C, and so does AIKO's Neostar 3S54. Put simply, every degree the cells sit above 25 °C costs about a quarter of a percent of output, and every degree below adds about the same.
Some rough arithmetic shows why that matters. On a cold, clear winter morning, cells sitting at 10 °C are 15 degrees under the test temperature, so the panel makes about 4% more than it would at 25 °C in the same light. On a hot summer afternoon, panels in full sun run well above the air temperature, and cells at 60 °C would be giving up around 9%.
Ballarat's summers help here. The Bureau's records give Ballarat Aerodrome a mean January maximum of 25.3 °C, against 30.4 °C at Bendigo Airport. Cooler panels on a bright day make more of the sun that is there.
Cloud, fog and frost
Winter in Ballarat is cloudy more often than not. Over the Bureau's 1957 to 2010 record, Ballarat averaged 55 clear days a year and 180 cloudy ones, and July averaged just 2.6 clear days against 19.2 cloudy days. Panels still make power under cloud, just less of it, and a day of broken cloud can still produce a useful amount around midday.
Foggy mornings work the same way. Output stays low until the fog lifts, and because the morning sun is weak in winter anyway, the middle of the day does most of the work.
Frost is common. The Bureau records an average of almost 16 days a year at or below 0 °C at the aerodrome, most of them from June to August. Frost on the glass generally clears as the sun reaches the panels, and the hours it costs are early hours of weak sun. As general advice, leave it alone: do not climb onto a frosty roof, and do not pour hot water on cold glass.
What this means for sizing
A few practical points follow from all of this.
- Know your winter numbers. A system that comfortably covers your daytime use in January will make a good deal less in June. That is normal, and it is worth seeing on paper before you decide on a size, rather than discovering it on the first grey week.
- North helps most in winter. The winter sun sits low in the northern sky. A north facing roof plane at a decent pitch faces it more squarely than the flat surface the Bureau measures, so it collects more of the winter light. East and west planes spread production across the day and still earn their place, especially on a roof with limited north space.
- Expect heating to change the evening. Ballarat averages 45 days a year at or below 2 °C. If you heat with electricity, your evening use climbs in exactly the months your panels make the least.
A battery in a Ballarat winter
Batteries are where the winter numbers matter most. A battery that fills by early afternoon every day in summer may only partly fill on a short, overcast June day, because the panels first have to cover the house before any surplus reaches the battery.
That does not make a battery a poor fit for Ballarat. It means the size of the battery and the size of the solar have to be looked at together, with winter in mind. Our guide to what size battery your home needs walks through how to do that from your own bill. On some plans you can also top a battery up from cheap or free grid power in the middle of the day, which is covered in charging a home battery from free power.
See it on your own roof
The quickest way to get a feel for this is to have a squiz at your own roof. Design your system online on an aerial photo of your home, try a north layout and an east and west layout, add a battery if you want one, and get a price for each. Every system includes remote monitoring and fault alerts, so you can watch your own summer and winter numbers once it is up and running.
