Image caption Global solar generation capacity increased by almost 30 gigawatts in 2011

The US has regained top spot from China as the biggest investor in clean energy in 2011, according to global rankings.

The table, published in a report by the Pew Charitable Trusts, showed that US invested more than $48bn (£30bn) in the sector, up from $34bn in 2010.

China slipped to second place, the authors reported, with investment only increasing by $0.5bn to $45.5bn.

Globally, overall financial backing in clean energy technologies hit a record $263bn, up 6.5% from 2010 levels.

The report, Who is Winning the Clean Energy Race , showed that G20 nations accounted for 95% of the investment in the sector (which does not include nuclear power).

The data, compiled by Bloomberg New Energy Finance, ranked the UK as seventh in the world, with $9.4bn of investment in 2011.

Over the course of the year, an additional 83.5 gigawatts (GW) was added to the world's clean energy generation capacity, including almost 30GW of solar and 43GW of wind.

"The sector continues to expand and is outpacing growth in the overall (global) economy. The sector reached its trillionth dollar of investment last year," observed Phyllis Cuttino, director of Pew's Clean Energy Program.

"We now have 565GW of installed (generation) capacity around the world. That outstrips nuclear installed capacity by 47%.

"So I think the facts fly in the face of those individuals who say this is a niche industry. This a growing and maturing sector."

Global clean-energy generation capacity 565 gigawatts (GW) TOTAL

239 GW - wind

184 GW - small hydro

73 GW - solar

57 GW - biomass and waste-to-energy

11 GW - geothermal

0.6 GW - marine (December 2011; source: Pew/Bloomberg)

She said market data showed that the US benefited in the short-term from attracting finances, however it was unlikely to be sustained.

"Investors rushed in to take advantage of expiring policies, such as tax incentives, loan guarantees, which expired at the end of 2011," Ms Cuttino told BBC News.

"So when we look at the very rapid rate of growth in investment here in the US, it is hard to see how that could be maintained without the policy mechanism that spurred that growth."

She suggested that there were signs that pointed towards a "drop off" in future clean energy investment as a result of "policy uncertainty".

China in previous years, on the other hand, had enjoyed rapid year-on-year growth, but it only recorded a $0.5bn increase during 2011.

Ms Cuttino said this was probably a result of the sector within the country maturing.

"The thing that is noticeable about China is that they are world leaders in terms of attracting asset finance, which is a measure of job creation and deploying renewables.

"This means they are really reaping the rewards of attracting a certain class of investment.

"They have a policy that not only attracts investment and deploys renewables, but actually manufacturers and exports as well.

Ms Cuttino said that all eyes would be on the Chinese during the coming 12 months because it had increase it target for solar generating capacity from 20GW by 2020 to 50GW by 2020.

"So it is going to be a good location for investment, as solar incentives decline in the US and Europe," she added.