But while renewable energy such as solar and wind power is close to surpassing gas in major nations, the United States is still bucking the trend.
Global energy think tank Ember released the findings in an analysis on Tuesday, which also predicted recent energy supply concerns in the Middle East could further deflate its popularity.
The report comes as the United Nations annual climate meeting begins in Germany to discuss clean energy targets, and after the Grattan Institute called for the federal government to phase out gas in Australia.
Ember's study analysed long-term trends in gas-fired energy generation around the world, including its share of the market in individual regions and in G7 nations.
It found the global market share for gas had dropped for a fifth consecutive year, falling from 23.9 per cent of electricity generation in 2020 to 21.8 per cent in 2025.
Gas experienced its biggest decrease in Japan, where use fell by 80 terawatt hours, followed by Vietnam (29 TWh), Brazil (25 TWh) and Turkey (21 TWh).
By contrast, solar energy generation grew 17 times faster than gas during 2025, the report found, and renewable energy almost overtook gas with just 33 terawatt hours separating the two.
The closing gap represented a fundamental change in global energy markets, Ember senior electricity analyst and report author Malgorzata Wiatros-Motyka said.
"Gas is steadily losing the advantages that once made it the default fuel for power system growth," she said.
Almost half of the nations using gas to produce electricity have passed their peak, the study found, including G7 nations Germany, the UK, Italy and Japan.
Gas use also declined in most of the world's regions during 2025, with Oceania registering a drop from 18.5 per cent in 2015 to 15.1 per cent of its energy mix in 2025.
Its use remained high in North America, the Middle East and Africa, however, due to abundant domestic supplies.
Disruptions to gas imports in the Middle East were likely to accelerate the slowdown in other nations, Ms Wiatros-Motyka said.
"Recent geopolitical crises (have) highlighted the risks of relying on imported gas," she said.
"Countries are increasingly turning to renewables because they are domestically available, more price stable and faster to deploy."
Gas represented 6.7 per cent of Australia's electricity generation in 2025, according to a recent Clean Energy Council report, compared to 13.9 per cent for rooftop solar.
The Grattan Institute has called for the federal government to reduce domestic gas use, including phasing out gas in households and supporting biomethane and hydrogen in industry.
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