2015 might have been a rough year for wind energy policy, but it was a great one for wind speeds. All over the country, onshore wind asset managers are breathing a sigh of relief that they have smashed their annual budgets.

But is this a little hasty? Our wind experts Rich Whiting and Bob Hodgetts have crunched the numbers to find out…

Best wind speeds in 15 years

The Everoze Wind Index shows how windy a period of time was. Through placing 2015 wind speeds in the context of the long-term average, the Index helps investors and asset owners benchmark their wind production against the wind resource, to check their own operational wind farms are performing as they should be. [1]

Our Index is unique in including a MW weighting, which accounts for the uneven distribution of wind projects across GB. This means that the Index shows the windiness of the regions specifically occupied by the GB fleet of wind farms, rather than just the general windiness of GB.

Overall, wind speeds were broadly strong until Autumn, when they plummeted relative to the long-term seasonal trend. But Father Christmas came to the rescue with gifts of strong winds over the festive period, helping the annual mean wind speed to recover from this blip. The result was the best calendar year of wind in over 15 years, which was 4.7% windier than the long-term average.

Energy generation from projects should be around 8% to 10% up

Of course, what investors, owners and financiers care more about is not wind speeds, but energy production. The rough rule of thumb is that the Wind Index can be multiplied by approximately two to estimate the change in energy production.

Given that the mean wind speed was 4.7% above the long-term average, this means that wind farm owners can only fairly pat themselves on the back if their project generated around 8% to 10% more energy than budget. Anything less, and your project is likely to be underperforming.  Individual project performance can be analysed more precisely through studying wind speeds on a local basis, and conducting project-specific operational assessments.

Additionally, investors need to be particularly cautious when evaluating potential wind acquisitions based on 2015 energy production – remembering that the bar should be set unusually high for this year. And asset managers pleased with last year’s figures should avoid becoming complacent.

So – until you’ve done your number-crunching, don’t crack open the champagne just yet. You might have smashed your budget, but did you make the most of this bumper year?

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Note 1:  Based on monthly mean wind speeds derived from reliable long-term data. The index is normalised to a value of 1.0 based on wind speeds from January 1996 to December 2015. The individual monthly values are a measure of the relative windiness of that month compared with the overall long-term mean. The index represents onshore wind only in Great Britain (GB).