A new report from Greenpeace says that for the world to switch from climate-altering fossil fuels to renewable energy by 2050 would cost about $A1.39 trillion per year.

But, they argue, the bill will be covered by lower energy costs.

On top of an estimated 600 billion euros per year already on the table for investment in renewables, Greenpeace argues that $US1 trillion ($A1.39 trillion) extra funding is needed to build enough green energy generators to replace coal, oil and gas-fired power stations.

But the analysts argue that this massive investment would be easily offset by the near $1.1 trillion saving in fuel costs.

It is the central argument of Greenpeace’s report “Energy (R)evolution”, which was written with input from experts at Greenpeace and the German Aerospace Centre.

“Because renewables don't require fuel, the savings... [until 2050] are $1.07 trillion per year, so more than meet the costs of the required investment,” a Greenpeace statement said.

Almost all nations are looking for ways to curb rampant emissions of climate-altering greenhouse gas, but the cost of the transformation is often held up as a major obstacle.

“The solar and wind industries have come of age, and are cost-competitive with coal,” said the report's lead author Sven Teske of Greenpeace.

He warned that the fossil fuel industry was “moving rapidly into irrelevance”.

“Every dollar invested in new fossil fuel projects is high risk capital which might end up as stranded investment.”

The report estimated the solar energy industry would generate as many as 9.7 million jobs by 2030.

That is more than 10 times as many as today, and close to the current number working in the coal sector.

Similarly, wind industry jobs could increase tenfold to nearly eight million.

The researchers used UN estimates for economic development and population growth to forecast that the world's energy will be completely “decarbonised” over the next 35 years.

They factored in rising energy demand in fast-growing regions like Africa and Asia, but said this would be offset by lower demand in rich nations to result in peak global demand by about 2020.

The study did use speculative assumptions that renewable energy costs would drop as the technology and availability improves.

The authors also said the expected short term electricity cost increases of about $0.02 per kilowatt hour.