Can wind-speed bin width change a turbine annual-energy calculation?

The short answer

Wind-speed bin width can change an energy estimate because each bin simplifies the range of speeds inside it. The effect depends on the turbine curve and the wind distribution. A wider bin is not inherently wrong, but its approximation should be tested where it could affect equipment comparison or feasibility.

Define how a bin represents its observations

Record the bin edges, represented hours and the rule used to evaluate power inside each bin. Using the midpoint, averaging actual interval outputs and interpolating a curve are different methods. They need not produce the same result near a steep curve change or operating threshold.

Keep the underlying observations when available. Once data are reduced to coarse counts, finer details cannot be reconstructed merely by drawing more bins in a later chart.

Run a controlled resolution comparison

Repeat the annual-energy calculation with suitably finer grouping while preserving the same valid observations, power curve, duration and losses. Compare the totals and identify the regions producing the difference. The exercise should isolate binning rather than change several modelling assumptions at once.

If only coarse published distribution data exist, report that limitation and consider a bounded sensitivity case. Do not invent an intra-bin distribution and label it measured.

Select a proportionate level of detail

Use sufficient resolution to make the decision stable within the wider uncertainty of the assessment. A negligible binning difference does not justify ignoring larger resource or siting uncertainties, while a material difference should be resolved before ranking closely matched proposals.

The handover should state the chosen binning convention and retain the comparison result. This lets another analyst reproduce the annual kWh figure and understand whether its apparent precision reflects robust evidence or simply a particular discretization choice in the spreadsheet.