To be able to evaluate the use of a subsidy as a way of solivng market failure.
The subsidy for onshore wind energy generation is to be cut by 10%, the government has announced. The Treasury is thought to have favoured a larger cut of up to 25%.
It is one of a number of cuts which the Department for Energy and Climate Change said should encourage up to £25bn in new investment in energy generation between 2013 and 2017.
The measures should also reduce the impact on household energy bills, it said, saving £5-£6 a year on average.
Under the current arrangements £44 of the average household bill would go towards renewables in 2013-14, rising to £50 in 2016-17.
Under the new subsidy levels, that will be £6 less in 2013-4, £5 less in 2014-5, but will be £1 higher in 2015-6 and £3 higher in 2016-7.
Energy firms pass on the cost of investing in new cleaner generation to consumers, and MPs on the Commons Energy and Climate Change Committee warned earlier this month that cutting subsidies too fast could increase bills.
What does the local council subsidise?