A BPC domestic consumer in a month purchases electricity at P1000.00 and receives 692.8kWh units but does not know how these come about. Another month the same consumer purchases with another P1000 and gets 714.5kWh. The consumer operates at 400V.

Can you educate this consumer on the various sub-charges that constitutes these charges and also advice why the number of units are different for the same amount. Show and explain with mathematical computation/model.