Does a wind turbine height limit refer to the hub or the blade tip?

The short answer

The applicable rule or project condition must define the height it limits. Hub height and the highest blade-tip position are different quantities. Confirm the reference ground level and the definition used by the relevant authority or land agreement, then compare that definition with the proposed installation drawing. Do not assume a quoted tower height is the same as the permitted overall height.

Make the geometry explicit

In a simple illustrative horizontal-axis arrangement, a hub 20 m above the stated reference level with a rotor radius of 4 m has an upper tip position of about 24 m above that level. Those are hypothetical dimensions, not MARSTON model specifications. Details of the installed geometry and the applicable measurement convention still need to be confirmed.

A proposal described only as a 20 m tower may leave ambiguity about the hub position, foundation projection or ground reference. Sloping ground can make an undefined reference especially confusing.

Ask for matching definitions

Term	What to identify
Tower height	The specified structural dimension and its end points.
Hub height	The rotor centre relative to a stated reference level.
Overall height	The upper extent of the installed system under the applicable definition.

The meaning of a local restriction is a matter for the relevant project reviewers; this example does not interpret a particular jurisdiction’s rule.

Review the consequences of a lower proposal

If the allowed height is lower than the initial concept, revisit wind exposure, rotor clearance, tower suitability and the energy assessment together. Reducing one dimension is not automatically an acceptable redesign.

Keep the agreed height definitions on the site drawing and in the equipment enquiry. The useful result is a consistent set of geometry records that the supplier, tower designer, installer and approval parties can compare without translating between different meanings of height.