We study the Hamiltonian of a two-dimensional log-gas with a confining potential V satisfying the weak growth assumption -V is of the same order than 2 log x near infinity -considered by Hardy and Kuijlaars [J. Approx. Theory, 170(0):44-58, 2013]. We prove an asymptotic expansion, as the number n of points goes to infinity, for the minimum of this Hamiltonian using the Gamma-Convergence method of Sandier and Serfaty [24]. We show that the asymptotic expansion as n → +∞ of the minimal logarithmic energy of n points on the unit sphere in R 3 has a term of order n thus proving a long standing conjecture of Rakhmanov, Saff and Zhou [Math. Res. Letters, 1:647-662, 1994]. Finally we prove the equivalence between the conjecture of Brauchart, Hardin and Saff [Contemp. Math., 578:31-61,2012] about the value of this term and the conjecture of Sandier and Serfaty [Comm. Math. Phys., 313(3):635-743, 2012] about the minimality of the triangular lattice for a "renormalized energy" W among configurations of fixed asymptotic density.