The word usually means one thing: a country that consumes a high share of its final energy as electricity. On that reading Japan qualifies, and the trouble with Japan is that its electricity is made from someone else's fossil fuels. An electrostate in the Plain Sight sense is an economy that is both deeply electrified and sovereign in the primary energy behind that electricity. Two conditions, not one.
The Electrostate Index
The two conditions are the two axes of the Electrostate Index, which carries the definitions, the readings and the direction of travel.
Why the term exists
Britain's industrial revolution ran on coal it owned. The American century ran on petroleum it controlled. China is assembling the first economy whose energy base is electricity it manufactures rather than fuel it extracts — and then selling the capability. Each previous era had a name for the country that supplied its energy; this one did not, because the arrangement is new. An electrostate does not sit on a resource. It builds the machines that make the resource unnecessary.
What the term is not
It is not a synonym for "renewable," which describes a generation source rather than a delivery form or an ownership question — a country burning its own coal is sovereign in it. Nor is it a claim that fuels disappear: industrial heat, aviation and the chemical feedstocks stay molecular well past the point where an economy qualifies.