Potential in general may be treated as an attribute of a point in space,
and may express the potential energy which a unit mass would have if
placed at that point.

This conception of potential is that of a property attributable to a
point in space, such that if a unit mass were placed there the forces
acting upon it would supply the force factor of energy, while the body
would supply the mass factor. This property is expressible in units,
which produce, if the supposed mass is a unit mass, units of work or
energy, but potential itself is neither.

Thus taking gravitation, a pound mass on the surface of the earth
(assuming it to be a sphere of 4,000 miles radius) would require the
expenditure of 21,120,000 foot pounds to remove it to an infinite
distance against gravity. The potential of a point in space upon the
surface of the earth is therefore negative and is represented by
-21,120,000*32.2 foot poundals (32.2 = acceleration of gravity). (See
Poundal.) In practice and conventionally all points on the earth’s
surface are taken as of zero potential.

[Transcriber's note; 21,120,000 foot pounds is about 8 KWh.]