The need for renewable energy is being addressed in such a positive light that the battle against climate change is looking positive, says energy policy expert Catherine Mitchell. The University of Exeter professor believes government policy has become far more flexible about renewable energy, and that the next few decades could lead us into an age that relies on sustainable resources.

Mitchell says in the journal Nature Energy that investment in renewables is now eclipsing that of fossil fuels. Countries heavily adopting renewable energy, including Denmark and Germany, have paved the way for other countries to use clean energy – showing that it can be done and, more importantly, how to do it.

"While the world is still dependent on fossil fuels, because energy systems have long lives, it has got to the point where more than half of the global electricity system investment is in renewables rather than fossil fuels," said Mitchell. "It is a sign that globally we have moved our public policy discourse and investor preferences from the old 'dirty' energy system to a clean one."

She says that more and more energy stakeholders, whether it be governments or the public, have begun to adopt a "no-regrets policy". That means more people are noticing the falling prices of renewable energy, and are believing there is no downside to using it.

Mitchell also points out that in 2012, renewable electricity capacity overtook the capacity of other forms of energy, including nuclear, gas and coal.

She adds, however, that this does not mean we have won the war on climate change. Governments need to continue backing their renewable policies, and make it quicker and easier for this clean energy to be used in everyday life.

"The recent United Nations meeting on climate change in Paris and its agreements has led to strong support for individual country's sustainable energy policies," said Mitchell. "However, these statements need to be backed up with appropriate governance – policies, institutions, incentives and energy system rules – to make sure they are implemented and are successful."

The US Energy Information Administration estimates that around 21% of total world electricity generation is from renewable sources. They expect this to increase to 25% by the year 2040.