Renewable energy's contribution to total energy in the National Electricity Market passed 10% in 2010 and 20% in 2018. By mid-2020 renewable energy's contribution was just shy of 25%. With a number of coal power stations approaching end of life and with wind and solar generation being the lowest cost forms of new energy available in Australia, large amounts of new renewable generation will be built through the 2020s. (For the purposes of this prediction, energy in the NEM includes energy generated "behind-the-meter" from solar panels, as predicted by AEMO, the energy market operator.)
Renewable Energy (solar, including "behind-the-meter" rooftop PV, wind, and hydro) will not exceed 50% of the total energy/electricity over a full year* (any start/end point) before …or for that matter after 2030. But make it by 2030 for the sake of the bet, and a relatively quick realisation of this folly, so actual decarbonisation of electricity can be tended to at the earliest opportunity.
*This share of the total electricity delivered into the NEM will be defined as the % of Renewable Energy electricity on a TWh basis of the total demand in the NEM for a year.
OpenNEM's dataset should be used for adjudication. If dataset is not available, Long Now will choose the closest analogous organization's data. If at any time before December 31 02030 there are 12 consecutive calendar months where renewables exceed 50%, the predictor wins.