With few facilities yet being commissioned, offshore cost data is also scarce. The data spread spans a costly experimental first wind farm in deep water far from shore and a project with its transmission link paid for by government. What it all means is that energy costs of offshore wind cannot be quantified with the level of confidence applicable to onshore installations. No meaningful conclusions are possible beyond those made in Windpower Monthly's recent survey of offshore costs (Special Report: Europe Offshore, September 2009).
Currently, most installed costs for offshore wind farms lie in a range of EUR2800-4000/kW. Operation and maintenance (O&M) costs range between EUR62-100/kW although, as with land-based wind power, the spread of estimates for O&M tends to reflect what is included in the contracts rather than fundamental differences in O&M practices.
Offshore generation costs, at the upper end of the cost range for a fully installed wind station on a site with a mean wind speed of 8 m/s are around EUR188/MWh, falling to around EUR132/MWh at the very best wind speed sites, such as far into the North Sea, where the mean wind speed is 10 m/s. Towards the bottom end of the installed cost range, offshore generation costs at a mean wind speed of 7 m/s are around EUR163/MWh, falling to around EUR128/MWh at 8.5 m/s. Offshore wind generation costs for the full range of wind speeds, presented for wind farms at four levels of installed cost, are graphically presented in the Europe Offshore Special Report.