The costs of renewable energy are going down all over the world.

This isn’t a new trend. Improvements in technology, government support, and the scaling-up of investments have driven down costs for years.

Already, it’s cheaper in most places to add a new renewable energy source from the power grid than a new fossil fuel source. And a new report from the United Nations found that within ten years renewable energy will be globally cheaper than fossil fuels.

But that doesn’t make renewable energy inevitable.

In many of what the UN calls “developing” countries, governments are, not unreasonably, most interested in delivering power to as many people as possible as soon as possible in order to improve quality of life and spur economic growth.

For many countries, that means building infrastructure and burning hydrocarbons, not developing more complex, and sometimes still-costly renewable power grids. India and many nations in Africa fall into this category, as they rush to meet the growing needs of their populations.

Among wealthier countries with already-established grids, the UN expects a mix of outcomes. Europe and Australia have the political will and resources to develop truly renewable grids, the UN reports. But others, most notably Japan and the US, are more reticent.

For Japan, space is an issue; it takes a lot more room to set up a wind farm or solar plant (and the necessary storage centres for days without wind and sun) than a fuel-burning facility. But an even bigger concern is the entrenched energy industry, which is unlikely to support a move to renewables and difficult to dislodge.

The US doesn’t suffer from the first problem, but it does from the second. While many fuel companies in the US recognise the challenge of climate change, the political party currently in power — almost unique among major political parties around the world — does not. With the current president working to dismantle green-energy policies and the Environmental Protection Agency administrator doubting climate change, forward motion seems unlikely.

China presents perhaps the most interesting case study. Like India and many growing parts of Africa, it has a large population rapidly increasing its economic output. And in the past, the US has pressured the Chinese political establishment to act on climate issues. But now the political will seems to exist in the emerging superpower to build a greener grid, and to even pressure the US to do the same. A truly renewables-based Chinese energy system seems at least possible.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.