By Paul Monies Business Writer pmonies@oklahoman.comCustomers of Oklahoma's two biggest electric utilities saved more than $65 million on their utility bills last year under a regional electricity marketplace established by the Southwest Power Pool, the Oklahoma Corporation Commission heard Thursday. The pool, which plans transmission, ensures reliability and operates a wholesale electricity market for Oklahoma and parts of 13 other states, said customers throughout its region have saved a total of $900 million since the market began in March 2014. Much of the savings came from lower fuel costs as utilities were able to draw from a wider variety of generation sources within the Southwest Power Pool.Read more on NewsOK.com