Wind turbines require a low wind speed in order to operate and the offshore wind turbines have a very high rate of operation. Moreover, what matters for energy policy is the overall output from any given technology, and while the wind may not be blowing in Devon it may be blowing in Suffolk, so we need to look at intermittency and the impact of the policy throughout the country.
I now want to turn to the impact of intermittency on the stability of the national grid. Research by the Royal Academy of Engineering shows that the grid can accommodate up to 26 GW of wind energy by 2020 without significant grid reinforcement being required, and that is split evenly between onshore and offshore wind—about 13 GW each—as my hon. Friend the Member for Wellingborough set out. We should not be complacent, however. Grid improvements are going to be needed to deal with intermittent renewables of all types and the increasing new nuclear programme. We cannot wait; we need to take action on that now—and, indeed, we are doing so. We will need to be innovative in terms of technology and operational and market incentives to meet this challenge.
I also want to address the point my hon. Friend made about constraint payments. Constraint payments occur when there is insufficient transmission network capacity between where the electricity is generated and where it is used. They are a long-standing part of the system, and to ensure the secure operation of the electricity system the grid is required to balance the supply and demand of electricity at all moments in real time. A cost-efficient transmission network will always have a degree of constraint by design. This system predates wind farms and most constraint payments continue to relate to fossil fuel generators, not wind farms.
National Grid has estimated that about 2% of total metered wind farm output was curtailed in 2013-14. In October 2012 we put a condition in generators’ licences to ensure they cannot profit unfairly from constraints. Constraint costs for wind farms have more than halved since, and we estimate that the total constraint costs of £340 million in 2013-14 represent about 0.7% or £4.20 of the average electricity bill. Of this, £47 million, or about 0.1% or 60p of the average household bill, relates to wind farms. In the medium and longer term, delivery of planned transmission investment will reduce these constraint payments, and there is upgrading work at the moment to ensure that happens.
Another issue that is often raised is whether wind farms actually deliver carbon savings. Wind power has one of the lowest carbon footprints compared with other forms of electricity generation. Work by the Parliamentary Office of Science and Technology published in 2011 looked at the carbon footprint of different forms of electricity generation. This carbon footprint assessment was calculated according to the “life cycle assessment” which aims to account for the total quantity of greenhouse gas emitted over the whole life cycle of a product or process—the making, transporting and erecting of wind farms, as well as their operation. The study found that there was a footprint of 488 grams of CO2 equivalent per kWh for a combined cycle gas turbine and 5.2 grams of CO2 equivalent per kWh for installations off the coast of Denmark. Further studies demonstrate that, even taking into account the whole life time impact on carbon emissions, wind farms have an incredibly low impact.
I want to address a point made by the hon. Member for Sunderland Central about the pipeline and industry. Our offshore wind pipeline is very strong. The UK has the most fully installed operational offshore wind capacity in the world—more than 4 GW as of March 2015—and we are committed to a further expansion, with the UK on track to generate around 10 GW by the end of the decade.
As the Prime Minister has said, onshore wind has an important role to play, and much has already been built and we are set for having 10% of electricity from onshore wind. Let me make it clear that we are committed, once we have reached this 10% which is in the pipeline already, to removing the subsidy and putting onshore wind into the planning system, and also to changing the planning system so that local councils have the decisive say. As the Prime Minister has said—and my hon. Friend read out—if they can make their case, they can, but I suspect they won’t.