Across Asia, governments are trying to boost renewables' share of the energy mix, but often, there's one big obstacle holding projects back: money.
"There's a huge surge in activity in this part of the world that's really leading the world in adding renewable energy capacity," Eugene Sullivan, principal investment officer at the International Finance Corp. (IFC), said at the Credit Suisse Asian Investment Conference last month. "What we don't see in this part of the world is many of the strategic investors."
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That's a huge difficulty for a region that the International Energy Agency estimates will need around $700 billion in energy investment through 2035. Globally, institutional investors likely can provide at most around 25 percent of renewable project equity investment and around half of the debt through 2035, according to a 2013 report from nonprofit researcher Climate Policy Initiative.
Within Asia, "there aren't that many names across the markets that can easily raise money" in the debt and equity markets, Sullivan said, although he noted that leaves a "lot of value" for investors.
Seeking returns
But many investors are holding back amid concerns about whether they'll see returns.
"The nature of project financing is you only get repaid from the cash flows that come from that project. You have to be very confident in the subsidy, the feed-in tariff continuing for that particular project," James Cameron, head of project and export finance for the Asia Pacific at HSBC, said last week. Places with a stable regulatory regime are seeing more interest, he said.
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Concerns aren't uniform across the region or even across different types of projects.
"A lot of these projects don't have the same history as conventional power," making the investments appear riskier, especially once concerns about technology advances and price fluctuations in equipment such as solar panels are factored in, said Mark Plenderleith, head of energy, mining and infrastructure project finance for Asia at law firm Freshfields Bruckhaus Deringer.
"Risks are lower if you've seen a track record," something Southeast Asia doesn't really have yet, he added, noting governments sometimes have trouble holding up their end of the deal even in developed markets.
Specific types of projects also face their own headwinds. For example, geothermal projects face difficulty finding financing due to high risk and high capital expenditure in the early phases of development, Plenderleith said.
Some success
There are successes. The Sarulla geothermal project on Indonesia's Sumatra island, expected to have around 330MW of capacity, managed to secure around $1.2 billion in financing from multiple sources, with construction starting around 25 years after planning began. The Rajamandala hydro-power project also managed to secure financing of around $150 million from Japanese sources last year.
But solar and wind projects can face more difficulty raising funds as they tend to be smaller and often have to be bundled into a package of 7-12 deals, Plenderleith said.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1