The chart is from data at AEMO Average Price Tables – and shows prices rising from the brief period of stability post June 2014 after the Carbon Tax was abolished. 
The closure of the last coal fired generation in South Australia in May 2016 preceded the price explosion in June. Then in July the “Safeguard Mechanism” administered by the Clean Energy Regulator kicks in and is designed to make large emitters purchase Australian carbon credit units (ACCUs) if their emissions exceed a baseline. So that would tend to add costs which probably pass on into electricity prices. It is intriguing that while NSW, Qld and SA have seen firm prices in Spring 2016 compared to pre-May – Vic prices have weakened. The reasons for the spikes in Qld prices late 2014 to early 2015 and again in Feb 2016 are not known but operational shutdowns could be a cause. Check NemWatch for realtime generation.
Saw AEMC chairman John Pierce on TV news.
South Australian power bills to increase by $115 after Hazelwood power station closure 14 Dec 2016
www.abc.net.au/news/2016-12-14/sa-power-bills-to-rise-after-hazelwood's-closure,-report-says/8117334?WT.ac=localnews_adelaide
They never address that there is yet no cost effective proven 24/7 solar of any type. All in the future no worries just send in your cheques.