Winter westerlies cause differences in rooftop solar energy in eastern Australia



In a new weekly update pv magazine, Solcast, a DNV company, presents the solar irradiance data it collected in Australia in June. The data showed eastern New South Wales received radiation intensities around 15% above normal in June, while central and western Victoria received a combined 10-20% below normal.

These fluctuations were caused by an unusually persistent low pressure in the Gulf of Australia. This system produced persistent westerly winds that carried cold and moist air from the Southern Ocean to southeastern Australia. However, the Great Divide on the mainland’s east coast forms a natural barrier that dries out these western parts, causing widely sunny conditions in eastern New South Wales – ideal for solar energy production.

Australia has very high rooftop solar penetration, with more than 17GW of installed capacity in more than a quarter of households, according to These plants are concentrated in state capitals, so weather conditions in Melbourne and Sydney have a big impact on output behind the meter.

Solcast API meters of solar on rooftops show that this weather will continue into July. In Victoria, inconsistent and overcast conditions are causing peak solar output to drop to as much as 25% of nameplate capacity. In contrast, solar performance in New South Wales is more stable, with daily peak generation consistently at 40-50% of nameplate capacity.

Solcast produces these numbers by tracking clouds and aerosols with an accuracy of 1-2 kilometers worldwide using satellite data and proprietary AI/ML algorithms. This information is used to drive irradiance models, allowing Solcast to calculate irradiance with high resolution, with a typical error of less than 2%, and also cloud tracking forecasts. This data is used by more than 300 companies that manage more than 150 GW of solar energy worldwide.

David is a passionate writer and researcher who specializes in solar energy. He has a strong background in engineering and environmental science, which gives him a deep understanding of the science behind solar power and its benefits. David writes about the latest developments in solar technology and provides practical advice for homeowners and businesses who are interested in switching to solar.

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