Getting power from the wind and the sun no longer seems like a hippie fantasy: Elon Musk is betting that solar power will be so profitable it will help fund space travel, and big tech companies like Apple and Google are buying in, too. Today most homes and businesses are still powered by fossil fuels, but in just a few decades — maybe even as little as 15 years — most energy could be coming from renewable sources.

An enormous new survey of industry experts shows how fast things are moving. Recently, DNV GL, an international energy consulting company, asked 1,600 people who actually work in the field — at equipment manufacturers, power producers, utilities, policy-making agencies, energy retailers, regulators, and equity investment firms — about the future of renewables. One of the main questions: How quickly will renewables be generating 70 percent of the energy in the markets you work with?

Almost half of the survey respondents said they could see that happening by 2030. And almost all of them — about 80 percent — thought renewables would dominate by 2050.

Here's why they're optimistic about renewable energy:

Politicians are supporting it. "It is mainly a political question. It is clear that a renewables-based electricity system is technically and commercially possible, perhaps by the middle of this century, but only if backed up by political support," one German respondent told DNV GL. It's not a given, but, increasingly, politicians — even American conservatives — are onboard with the idea that the future of energy includes wind and solar power.

Energy storage is getting better. Two thirds of the DNV GL survey respondents chose energy storage as one of the top three technologies needed for renewables to work. (The other two: smarter grids and more money to build them.) And storage technologies are improving: This week, for example, Tesla is expected to announce that it's releasing a "home battery" that could help store power generated by rooftop solar panels. This is key to convincing people that renewable energy can be relied on — and making sure that's true.

Investment in renewable power is growing. Bloomberg New Energy Finance reported this week that in 2014 $270 billion was invested in renewable energy, about one fifth more than the year before. The largest portion of that money was going to projects in developing markets — Brazil, Indonesia, Chile, Mexico, Kenya, and China, where investments totaled $83.3 billion.

In other words, power, technology, and money are all aligning behind the same idea — that in the next few decades the way we power the world will change, dramatically. The only real question is how fast.