Recently many authors have calculated energy of the Friedman universes by using coordinate-dependent double index energy-momentum complexes in Cartesian comoving coordinates (t,x,y,z) and concluded that the flat and closed Friedman universes are energy-free. In this paper by using Einstein canonical energy-momentum complex and by doing calculations in conformally flat coordinates we show that such conclusion is incorrect. The results obtained in this paper are compatible with the results of our previous paper, see J. Garecki, Found. Phys. 37, 341 (2007), where we have used coordinate-independent averaged energy-momentum tensors to analyze the energy of Friedman universes.

PACS numbers: 04.20.Me, 04.30.+x