By Roger Harrabin
Environment analyst, BBC News
The European Union is expected to tell the UK that 15% of energy needs must be met from renewable sources by 2020.
The EU wants to create a low-carbon economy across Europe
The figure, currently about 2%, will include all energy used for heating and cooling buildings.
Experts have called the target challenging because they say heating and cooling are hard to achieve on a mass scale using renewable fuels.
The EU, which is trying to create a low-carbon economy in Europe, will announce its decision next week.
Tough but achievable
As current heating and cooling technologies are unproven on a mass scale, electricity generation is expected to meet much of the target - primarily through offshore wind, however the government is also looking favourably on the prospect of a tidal barrage across the Severn.
It is expected that the UK will have to obtain between 30% and 40% of its electricity from wind, wave and solar sources by 2020 - up from the current level of 5%.
"The target is do-able but only if we really pull out all the stops," observed Gordon Edge, head of offshore energy at the British Wind Energy Association.
He said there was still a problem with "interconnectors", cables that transport the electricity from the offshore wind farms to the National Grid.
Mr Edge added that following years of scepticism from the government's industry department, civil servants were now asking: "What can we do to help? There has been a huge change in attitude."
The UK's expected 15% target is a share of the total EU target of gaining 20% of energy from renewables by 2020.
The share is calculated on nations' existing levels of renewable power and Gross Domestic Product (GDP).
A government spokesman would not confirm the 15% figure but pointed out that Prime Minister Gordon Brown, in a speech shortly before Christmas, said that the UK would hit whatever target it was given.
In the autumn, he overruled an attempt by the business and enterprise department to get the targets redefined to make them less onerous.