  This paper examines the behavior of the dimensionless dissipation rate
$C_{\varepsilon}$ for stationary and nonstationary magnetohydrodynamic (MHD)
turbulence in presence of external forces. By combining with previous studies
for freely decaying MHD turbulence, we obtain here both the most general model
equation for $C_{\varepsilon}$ applicable to homogeneous MHD turbulence and a
comprehensive numerical study of the Reynolds number dependence of the
dimensionless total energy dissipation rate at unity magnetic Prandtl number.
We carry out a series of medium to high resolution direct numerical simulations
of mechanically forced stationary MHD turbulence in order to verify the
predictions of the model equation for the stationary case. Furthermore,
questions of nonuniversality are discussed in terms of the effect of external
forces as well as the level of cross- and magnetic helicity. The measured
values of the asymptote $C_{\varepsilon,\infty}$ lie between $0.193 \leqslant
C_{\varepsilon,\infty} \leqslant 0.268$ for free decay, where the value depends
on the initial level of cross- and magnetic helicities. In the stationary case
we measure $C_{\varepsilon,\infty} = 0.223$.
