Cameron was speaking at the Clean Energy Ministerial (CIM) in London, which is being attended by 23 energy ministers from around the world. Last year's event was in Abu Dhabi, UAE.
The UK government also announced a second round of offshore innovation funding – of up to £5m - targeted straight at technologies that can cut the cost of energy, particularly in offshore.
However, the UK prime minister has come in for criticism over a failure to make a keynote speech at the event. In the words of one commentator, Cameron presented a "five minute Q&A session and a 'press release on the side'".
"Britain has gone from virtually no capacity for renewables, to seeing them provide almost 10 per cent of our total electricity needs last year," said Cameron. "And we’ve added more capacity for renewables in the last two years than at any time in the last decade.
"Our commitment and investment in renewable energy has helped to make renewable energy possible. Now we have a different challenge. We need to make it financially sustainable."
The Clean Energy Ministerial (CEM) is a high-level global forum to promote policies and programmes that advance clean energy technology.
The 23 governments participating in CEM initiatives are Australia, Brazil, Canada, China, Denmark, the European Commission, Finland, France, Germany, India, Indonesia, Italy, Japan, Korea, Mexico, Norway, Russia, South Africa, Spain, Sweden, the United Arab Emirates, the United Kingdom, and the United States.