We report molecular simulations of different graphene-water interfaces. Our aim is to calculate the interfacial tension as accurately as possible for a reasonable computational time by tuning on the value of the cutoff radius and the way of calculating the electrostatic interactions. We focus on the structure of water close to the graphene surface and on the profile of the interfacial tension along the direction normal to the surface. We then compare the Ewald summation method with two versions of the Reaction Field technique in different graphene interfaces.