Transverse energy ($E_T$) has been measured with both of its components, namely hadronic ($E_T^{had}$) and electromagnetic ($E_T^{em}$) in a common phase space at mid-rapidity for 62.4 GeV Au+Au collisions by the STAR experiment. $E_T$ production with centrality and $\sqrt{s_{NN}}$ is studied with similar measurements from SPS to RHIC and is compared with a final state gluon saturation model (EKRT). The most striking feature is the observation of a nearly constant value of $E_T/N_{ch} \sim 0.8$ GeV from AGS, SPS to RHIC. The initial energy density estimated by the boost-invariant Bjorken hydrodynamic model, is well above the critical density for a deconfined matter of quarks and gluons predicted by lattice QCD calculations.