Rooftop PV Capacity in the SWIS – January 2021 Edition

Now that 2020 is finally behind us, let’s dig into the data and pull out the latest estimates for rooftop PV capacity in the South West Interconnected System (SWIS), Western Australia’s largest electricity grid.

Here are the headline numbers:

Rooftop PV Capacity (MWp)01/01/202001/01/2021Change
Total small-scale capacity1,281.21,576.6295.4
Total large-scale (>100 kW) capacity25.429.23.8
Total rooftop PV capacity1,306.61,605.8299.2

Despite COVID-19, there was robust growth in small-scale (mainly residential) rooftop PV installations in 2020, with over 295 MW installed compared with 240 MW in 2019 (a 23% year-over-year growth).

Meanwhile, large-scale installations slowed down significantly from 13.1 MW in 2019 to just 3.8 MW in 2020.

The aggregate rooftop PV capacity of 1,605.8 MW has now overtaken the combined capacity of the coal-fired power stations in the SWIS (Bluewaters, Collie and Muja C/D have a combined maximum capacity of 1,566.9 MW).

The cumulative rooftop PV capacity in the SWIS since 2007 is shown in the graph below:

As can be seen from the graph above, rooftop PV capacity growth has accelerated in the past few years. It remains to be seen whether installations will continue to grow at the same pace with the reduction in the feed-in tariff in November 2020. The answers to the following questions will likely determine whether there will be continued growth or saturation in the demand for new rooftop PV systems:

  • How sensitive are prospective buyers to the implied investment returns / payback period on new PV systems?
  • Will owners of older existing systems with expired grandfathered feed-in tariffs begin to upgrade to larger systems?
  • Will there be an uptake in battery energy storage systems to take advantage of falling prices and higher feed-in tariffs during peak times?
  • Will new housing developments / construction include rooftop PV as a standard feature?
  • Will an uptake in electric vehicle purchases incentivise owners to install larger rooftop PV systems for charging (and possible vehicle-to-grid) purposes?

Data sources and notes

All of the data used in this analysis is sourced from the Clean Energy Regulator (CER) website:

The postcode data for small- and large-scale installations is filtered for postcodes in the SWIS. Large-scale ground-mounted installations are also removed from the data set (e.g. Merredin solar farm or Greenough River solar farm). The coarseness of the postcodes at the edges of the SWIS may introduce some error into the statistics, but the volume of installations in these areas are small relative to the total number of installations.

The small-scale postcode data was extracted on 25 January 2021, and it appears that the data set for December 2020 is not yet fully complete (showing only 2,295 installations for December 2020 compared with a monthly average of 3,759 installations over the period from January 2020 to November 2020). That said, the reduced volumes could potentially reflect softening demand after the REBS scheme was replaced by the DEBS scheme and the tariff reduced to $0.03/kWh during the day after 6 November 2020 (though such a sharp drop-off seems unlikely).

Note that the quoted dates are actually accreditation dates, which may not necessarily line up with the actual installation dates. This is more of an issue with the large-scale installations (>100 kW). For example, a rooftop PV system is installed and it may be months before the proponent applies for accreditation.