10GW of extra offshore wind turbines by 2020 – The Real Costs

Projected 10GW in offshore wind turbines by 2020 to add 5% to electricity and gas bills, and reduce UK CO2 emissions by nearly 2%. Cost to exceed benefits by 3.8 or 27 times.


The Telegraph has an article “Offshore wind farm scrapped due to fears over birds

A 200MW extension to the 630MW London Array has been abandoned “over the impact on the red-throated diver, a bird classified as rare or vulnerable by the European Commission“. However,

Ministers say they want between 8GW and 15GW built by 2020, up from 3.6GW now, and suggest a total of about 10GW is most likely.

My comment on this (with references) is

Some statistics to put the 10GW of extra offshore wind power by 2020 in perspective.

Offshore wind power operates at about 35% of nameplate from DECC figures1.

So that will produce about 30,660,000 Mwh of electricity.

At present each megawatt of offshore wind gets 2 renewables obligations certificates, worth £842,8. So that will add £2575m to bills, or about 5%3 of 2012 Electricity AND Gas bills.

But this will help reduce the UKs Carbon emissions. How much?

RenewableUK reckons that each megawatt hour of renewable electricity saves 430kg of CO2 emissions4. So that equates to 13.2 mt, or 1.84% of the 716.4 mt6 1990 baseline emissions.

This has a value as well, called the “social cost of carbon”. The Stern Review reckoned $85t/CO25. The UNIPCC said the average was $126. So that is £675m or £95m towards saving the planet for future generations. Costs are either 3.8 or 27 times the benefits.


The costs of £2575m are not the full costs. There are also extra transmission costs, and backup capacity. A more sceptical view would put a much lower social cost of carbon than the $12 of the UNIPCC.

From note 5, the marginal abatement costs of offshore wind turbines are 3.8 times Stern’s estimate. Perhaps somebody should ask Lord Stern where the marginal abatement costs of less than $85 per tonne of CO2 are to be found. There are millions of households and businesses in this country who would love to know.


  1. DECC stats here, spreadsheet “Renewable electricity capacity and generation (ET 6.1)”. Offshore wind was 35.2% of nameplate in 2012.
  2. https://www.ofgem.gov.uk/ofgem-publications/58136/buy-out-price-and-mututalisation-ceiling-201314.pdf.
  3. In 2012 the big six energy companies charged about £44bn to all customers. 5% rise assumes they have 85% of the market. Graph here, from this article.
  4. From http://www.renewableuk.com/en/renewable-energy/wind-energy/uk-wind-energy-database/figures-explained.cfm, last section “CO2 Reductions (p.a.) in Tonnes”.
  5. The Stern review noted on pages xvi-xvii

    Preliminary calculations adopting the approach to valuation taken in this Review suggest that the social cost of carbon today, is of the order of $85 per tonne of CO2……. This number is well above marginal abatement costs in many sectors.

  6. The UNIPCC AR4 Summary for Policymakers in 2007 stated on page 22.

    Peer-reviewed estimates of the social cost of carbon in 2005 average US$12 per tonne of CO2, but the range from 100 estimates is large (-$3 to $95/tCO2).

  7. Source World Bank data. UK data at http://data.worldbank.org/country/united-kingdom
  8. The current banding is at https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/211292/ro_banding_levels_2013_17.pdf

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Kevin Marshall