power stations. Backup and Frequency Response There is some dispute over the necessary amount of reserve or backup required to support the large-scale use of wind and solar energy due to the variable nature of its supply. In a 2008 submission to the House of Lords Economic Affairs Committee, E.ON UK argued that it is necessary to have up to 80–90% backup. Other studies give a requirement of 15% to 22% of installed intermittent capacity. National Grid, which has responsibility for balancing the grid, reported in June 2009 that the electricity distribution grid could cope with on-off wind energy without spending a lot on backup, but only by rationing electricity at peak times using a so-called "smart grid", developing increased energy storage technology and increasing interconnection with the rest of Europe. In June 2011, several energy companies including Centrica told the government that 17 gas-fired plants costing £10billion would be needed by 2020 to act as back-up generation for wind. However, as they would be standing idle for much of the time they would require "capacity payments" to make the investment economic, on top of the subsidies already paid for wind. In 20152016, National Grid contracted 10 coal and gas-fired plants to keep spare capacity on standby for all generation modes, at a cost of £122million, which represented 0.3% of an average electricity bill. Grid scale battery storage is being developed in order to cope with the variability in wind and solar power. , 1.3GW of grid storage batteries was active, along with the traditional 2.5 GW of pumped storage at Dinorwig, Cruachan and Ffestiniog. With the increase in proportion of energy being generated by wind and solar on the UK grid, there is a significant reduction in synchronous generation. Therefore, in order to ensure grid stability, the National grid ESO is piloting a range of demand side and supply side frequency response products. Public opinion Surveys of public attitudes across Europe and in many other countries show strong public support for wind power. About 80 per cent of EU citizens support wind power. A 2003 survey of residents living around Scotland's 10 existing wind farms found high levels of community acceptance and strong support for wind power, with much support from those who lived closest to the wind farms. The results of this survey support those of an earlier Scottish Executive survey 'Public attitudes to the Environment in Scotland