Rooftop Solar System Sizes Decline Amid Battery Rebate Changes
The rooftop solar market in Australia is experiencing significant growth, largely fuelled by the ongoing popularity of home batteries. Recent data reveals that in 2026, more photovoltaic (PV) capacity has been installed so far this year than during the entirety of 2025.
A report from SunWiz has highlighted that the rise of affordable home batteries is not only boosting the uptake of solar panels but is also influencing the size of the solar systems being installed. When the federal rebate was first introduced, many households opted to either install larger than normal rooftop solar systems or expand their existing setups to take full advantage of the sizable 50 kilowatt-hour (kWh) batteries available at a significant discount.
Changes in Rebate Influence Solar Installations
With recent adjustments to the battery rebate, which now encourages the installation of batteries closer to the 20-25 kWh range, there has been a noticeable decline in the average size of rooftop solar systems being installed through the Small-scale Renewable Energy Scheme (SRES).
According to SunWiz, the national average rooftop solar system reached 9.98 kW in September, a slight increase from August’s 9.86 kW, significantly up from the twelve-month low of 9.35 kW recorded in May when the battery rebate was altered. However, this average still falls short of the April peak of 11.75 kW and December’s high of 12.07 kW, indicating some fluctuations in system sizes over recent months.
Market Dynamics and Capacity Growth
SunWiz managing director Warwick Johnston noted that the 10-15 kW category continues to dominate the market, contributing a total of 105.94 megawatts (MW) in September alone, more than double the next largest size cohort, 6-8 kW, which saw 53.04 MW, while the 15-20 kW sector contributed 43.41 MW.
In total, Australia saw the installation of 311.8 MW of new rooftop solar capacity in September, recovering from a downturn in August when only around 290 MW was added. This figure marks the second-strongest month following April’s impressive high of approximately 505 MW.
Record Installations and Battery Trends
The cumulative total from January to September sets a new record, outpacing last year’s figures by 43 per cent at the same point in time. In terms of home battery installations, SunWiz reported nearly 1 gigawatt-hour (GWh) for September, with approximately 966.5 megawatt-hours (MWh) added, a 12.5% increase from August and marking the strongest month since the April peak of 3,262 MWh prior to the rebate adjustments.
As the battery market stabilises at close to 1 GWh per month in the wake of the pre-May surge, there is a growing trend in average battery sizes, with 45% of new batteries now exceeding 30 kWh. Johnston remarked that even as the average size of rooftop solar systems declines, the average battery size is experiencing a slight recovery from its April low.
