Across much of the globe, there is an insatiable hunger for energy to fuel growing economies. While the U.S. and Europe could see relatively flat-lined energy use in coming decades, it will rise considerably in non-Organization for Economic Cooperation and Development (non-OECD) countries between now and 2040, according to the U.S. Energy Information Administration (EIA).

Asia, and particularly China and India, will lead the charge toward a 56 percent increase in energy consumption by 2040. Although renewables and nuclear are growing at the fastest rates in the electricity sector, it will not be enough to dethrone coal, according to the EIA.

EIA’s forecast shows non-hydropower renewables as still just a small piece of the electricity generation mix in 2020, with coal still trailed by natural gas. Nearly 80 percent of the world’s energy use, for both transportation and electricity, will be fossil fuels through 2040.

But many forecasts have underestimated renewable growth. The International Energy Agency recently revised its projected installation for global renewables upward. In 2003, the IEA projected that non-hydro renewables would represent about 4 percent of global generation by 2030 under an aggressive policy scenario, but the industry reached that figure in 2011.

The EIA found that half of the increase in the world’s energy use will come from China and India. And while China is building every type of generation as fast as it can, including coal, gas, nuclear and renewables, India’s mix could be very different.

A report earlier this year from HSBC found that wind is already cost-competitive with coal in India, and solar is not far behind. Part of the competitiveness is because wind and solar PV energy production do not require a lot of water.

The EIA noted many uncertainties, including long-term economic issues in the U.S., Europe and China; social unrest in the Middle East and North Africa; shale gas production; OPEC market decisions; and climate policies. But there is one other issue that could severely impact energy choices in the next 30 years that EIA left off the list: water.

For the first time ever, India has identified water as a scare natural resource in its most recent five-year plan. Last year, India curbed some thermal plants’ output during droughts because of lack of water for cooling.

Chris Nelder noted in an article that a recent study found that conservative renewable estimates, such as those by the EIA, were consistently too low compared to more optimistic outlooks.

For other developing nations, adopting renewables paired with smaller grids may make more sense in places where there is no reliable electricity and people pay high prices for electricity from diesel generators. More than 1.3 billion people live without regular access to electricity.

China is still the 800-pound gorilla in the room, as it consumes nearly as much coal as the rest of the world combined. And while China is reportedly changing its taxation policy on greenhouse gases, it’s unclear whether any changes will temper its appetite for fossil fuels in coming decades.