Societies have traditionally aligned their activities with the weather, such as planting crops at specific times to avoid conflicting agricultural calendars. As climate risks rise and technology evolves, solar-rich regions should adapt their economic activities to take advantage of the sunlight. Better matching peak electricity demand with solar supply can reduce costs, green the grid, and enhance reliability. Australia and other sun-rich economies should consider changing their clocks to harness the sunlight hours later in the day to better align clean electricity supply with consumer demand.
Solar photovoltaics have become the cheapest form of electricity generation in most countries around the world and could become even more competitive as complementary technologies – especially batteries – become more efficient. They also require virtually no water for cooling, a significant advantage over most other generation sources.
Shifting sunlight hours to later in the evening – for instance, a 10PM sundown – could better align solar generation with peak demand.
However, solar faces challenges. Its output peaks at midday, while maximum electricity demand occurs in the late afternoon and evening, driven by societal habits. This misalignment creates the “duck curve”, where non-solar resources, especially natural gas, must ramp up as solar output declines. Additionally, solar generation can be “curtailed” – thrown away – if the amount of generation overwhelms demand, transmission capacity, or both.
Shifting sunlight hours to later in the evening – for instance, a 10PM sundown – could better align solar generation with peak demand, decrease curtailment, and increase penetration rates of clean electricity, especially with the use of long-duration batteries. Indeed, researchers from Australia and South Korea found, in a 2013 analysis conducted in Western Australia, that daylight savings time had little effect on overall demand but – crucially – redistributed consumption from the late afternoon and early evening to cooler parts of the day.
This approach optimises solar power use, enhancing energy security and resilience even amid rising temperatures. Regions with abundant solar resources, such as Australia, northern China, California, and parts of Latin America, should consider adopting solar alignment time. Without this adjustment, solar generation will hit the “solar wall”, where it becomes economically or technically impossible to add more solar to the grid.
California, one of the world’s most mature solar markets, has already hit the solar wall, with curtailment rates rising sharply in 2022 and 2023. However, the California Independent System Operator (CAISO) has mitigated this by expanding transmission and battery storage, leading to a record 22 per cent solar share of 12-month trailing in-state demand in August 2024 while limiting curtailment.
Despite these laudable achievements, California will eventually run into the solar wall again and will likely need a battery breakthrough, a change in policy, or both.
Australia is also on the verge of the same phenomenon. At a national level, solar accounted for 16 per cent of all electricity generation in 2023 – impressively up from less than 3 per cent in 2016, but close to hitting the solar wall. Renewables curtailment, mostly from solar, rose 40 per cent in 2022, according to the Australian Energy Market Operator (AEMO).
While Australia shouldn’t rush headlong into changing its clocks, changing technologies and decarbonisation needs suggest new approaches are preferable.
Like California, Australia is taking steps to reduce curtailment. Grid-scale battery storage installations hit a record 1,410 MWh last year, and a major transmission project was recently approved in New South Wales. While these measures help, more will be needed.
Switching to permanent solar alignment time could cause societal disruptions, especially for early risers and groups such as trade professionals and parents of school-aged children – who may rely on morning sunlight. It could also spark a political backlash, as some will rail against changes to the status quo. Leaders could limit these issues by carefully framing the benefits of solar alignment time, especially its ability to lower costs and decrease water usage, especially in water-scarce regions. Additionally, phasing in the program slowly could encourage greater buy-in.
Solar alignment time could also increase overall curtailment by boosting summer generation but causing overproduction in autumn and (especially) spring when electricity demand is low amid moderate temperatures. Evening cooling and morning heating electricity needs might also rise, offsetting the climate and pollution benefits from solar-based electricity if fossil fuels are used instead. Complementary technologies such as batteries and transmission, when economical, could limit these risks. And in any event, curtailment levels are less important metrics than costs, emissions, reliability, and pollution.
While Australia shouldn’t rush headlong into changing its clocks, changing technologies and decarbonisation needs suggest new approaches are preferable. Better aligning solar supply with peak electricity demand could enable Australia and other sun-rich regions to secure cheap, clean power.
The views presented in this article are the authors' own.
