A consistent set of thermodynamical relations for a strongly coupled many-quark system at finite temperature and vanishing baryon number density is derived within the Hartree approximation. Confining interactions are assumed to be saturated within colour singlet quark-antiquark pairs. For a system of massless quarks, simple analytical expressions for the pressure and the energy density are obtained and compared with those of a standard thermodynamical bag model of non-interacting quarks and gluons. We observe that the two equations of state have similar thermodynamical behaviour. A qualitative comparison with results from lattice gauge simulations (LGS) shows that the saturation of energy density above the chiral transition can be interpreted as being due to dynamically confined quark matter.