Australia's large-scale renewable energy target was cut in July 2015 to 33TWh by 2020.
The cut followed a fierce political debate, which practically froze development of wind projects for over a year.
The RET subsidy programme was introduced in 2009, with an initial target for large-scale renewables to produce 41TWh by 2020. The 33TWh target is expected to produce approximately 23.5% of Australia's electricity demand.
Progress towards the 2020 target is "adequate under the circumstances", according to the Clean Energy Regulator, the government body responsible for administration of carbon reduction legislation.
The report concludes that a further 6GW of installed capacity will be required to meet the target, half of which must be committed to in 2016 to make "satisfactory progress".
It notes that just 409MW of renewables was committed to in 2015.
"Ideally the majority of this additional 6GW capacity would be committed in 2016 and 2017 to avoid a shortage of large-scale generation certificates on the path to the 2020 target," according to the report.
The 6GW of capacity is expected to be made up by 75% of wind projects with the remainder from solar. However, if less than 3GW is committed to in 2016 the share of solar will increase due to the quicker build time, the report warned.