While the hair shaft itself, the part we see and style, is essentially dead and doesn’t consume energy, the hair follicles beneath the scalp are very much alive. These follicles, where hair growth originates, are metabolically active and do require energy to produce and push out new hair strands. This energy is derived from the nutrients we consume. So, in a nuanced way, yes, the process of hair growth does expend energy, but the hair strand itself doesn’t ‘spend’ energy in the way muscles do during activity.