Prime Minister David Cameron has said he "passionately believed" the growth of renewable energy is vital to the UK's future.
Speaking specifically on the environment for the first time since pledging to lead "the greenest government ever", he said the UK was the best placed in the world for green energy, investment and jobs.
But he told ministers from 23 countries at a clean energy meeting in London that renewable energy needed to be "financially sustainable".
"We don't just need greener energy, we need cheaper energy," Prime Minister cameron said, warning families were struggling with bills in the face of higher gas prices.
He said that renewable energy was still relatively expensive, although the cost of solar and onshore wind farms had fallen and the Government would work with industry to reduce the costs of offshore wind.
The Prime Minister said he believed renewables could be among the cheapest sources of energy for the UK within years.
He said that when the costs of renewables fell, it was right that consumers should pay less in green subsidies.
In a move to reassure companies who have been hit by policy uncertainty - embodied by the cuts to solar subsidies for households - he promised: "When we have made a commitment to a project we will always honour it in full."
"Of course, nuclear energy, cleaner coal, oil and gas -including shale gas - and carbon capture and storage are all going to have a role to play," the Prime Minister said.
"I passionately believe the rapid growth of renewable energy is vital to our future."
Answering critics of his environmental policies, he said: "When I became prime minister I said we would aim to have the greenest government ever; that's exactly what we have.
"Today we are one of the best places for green energy, green electricity, green investment and crucially green jobs."
The growth in renewables in the UK was not just good for the environment, but "good business" too, he added.
The Prime Minister announced a new industry partnership to make the most of the North Sea's renewable resources, such as offshore wind.
And companies have announced £350 million of new investment in UK renewables today, representing 800 jobs, including a £300 million biomass project by Helius Energy at the Port of Bristol.