Loading "However, if both power station outages were extended over the summer, and if no additional supply was secured, involuntary load shedding may be experienced in Victoria during extreme weather events, potentially over multiple events, equivalent to between 260,000 and 1.3 million households being without power for four hours," it said. While strains on the grid have a become a feature of recent summers - such as last January in Victoria and South Australia - the coming season may be particularly trying especially in Victoria. The reliability of coal-fired power stations is one factor as they age. The 500-megawatt Loy Yang A unit failed because of an electrical short in May, and will likely require a major rewiring. In the Mortlake case, a 259MW unit suffered an electrical fault in July and also will need months to fix.

Victorian Energy Minister Lily D'Ambrosio said last summer demonstrated that the state's aging coal-fired power stations, owned by private energy companies, were shown to be "unreliable, particularly at times of high demand". "We’ve been saying this for a long time and that’s why we’re investing so heavily in renewable energy," she said. Ms D'Ambrosio said the "biggest threat to reliable energy supply in coming years is the complete lack of a national energy policy. Angus Taylor need to look at the facts staring him in the face." Federal Energy Minister Angus Taylor has singled out Victoria's ability to cope with the summer peak as a grave concern, accusing the Andrews state government of policy failures including encouraging the "premature" shutdown of coal-fired power stations, banning onshore gas projects and moving too quickly towards renewable energy without firming capacity to support it. In response to the AEMO's report, Mr Taylor said meeting the reliability standard was "no guarantee that the lights won't go out in Victoria this summer".

"In 2018, Victoria barely met the standard and 200,000 customers lost their power," he said. "When Victorians flick the switch, they need to be confident the lights will turn on - and stay on." Bruce Mountain, director of the Victoria Energy Policy Centre, said "on our own analysis, there's a lot to be worried about". Dr Mountain, though, cautioned against blaming Victoria's efforts to accelerate new supplies of wind and solar energy. "It's the failure of new gas and old coal" behind the current squeeze, he said. "Without that additional wind and solar, our issues would be more severe." "There's no doubt that if it is a very hot summer that things could be quite tight," Catherine Tanna, managing director of EnergyAustralia, said on Wednesday.

EnergyAustralia views said the abrupt closure of the 1600-megawatt brown coal-fired power plant in Victoria's Latrobe Valley in March 2017 as the key shift in supply even with the expansion of renewables since then. "Hazelwood was our spare tyre and now we don't have one," Jack Kotlyar, head of strategy at EnergyAustralia executive, said. The AEMO report noted efforts are underway to boost supply. The organisation is working with the Victorian government and industry "to secure the maximum permissible reserves" via its Reliability and Emergency Reserve Trader (RERT) scheme to ensure Victoria’s supply meets reliability standards this summer. The RERT rewards big energy users who agree to reduce consumption, and was triggered twice last summer in Victoria and South Australia. AGL, which represents 20 per cent of the national generation market, earlier this month said reliability was an important concern “in any market that is relying on old plants”.