The Government is over-investing in onshore and offshore wind farms, according to a think tank.
The Adam Smith Institute report The Limits Of Wind Power claims the investment in Britain and America is misguided.
In the report, released on Monday, the authors say wind energy "will never be suited as the lone or primary source of grid electricity due to its variable nature and will not deliver the environmental benefits expected".
Wind energy needs either expensive energy storage facilities or reserve power generation facilities to provide for users' needs, the authors say.
And the report, released jointly with the US's Reason Foundation, claims "wind energy is intermittent and therefore these back-ups are needed to avoid blackouts".
The paper argues that the practical upper limit for wind power's contribution to an electricity grid is 10% of the total energy mix - rather than the 2020 aim of between 8% and 15%.
"Very high wind penetrations are not achievable," said William Korchinski, author of the report.
"As wind's share increases, system reliability will be adversely affected disproportionately - unless adequate reserve power is available.
"That power reserve is expensive and lowers any possible environmental benefits."
UK 
