Does anyone know - or know how to figure out - how much power is 'stored' at any given time in the globe's power transmission lines? Intuitively, this must be a

Does anyone know - or know how to figure out - how much power is 'stored' at any given time in the globe's power transmission lines? Intuitively, this must be a pretty huge amount - basically 1x the global power consumption at any given instant? Anyone know if there's any/much spare capacity, that could actually be used as a massive distributed battery?