That is, single precision calculations use half the memory (or disk) space and produce a speedup factor of 2 on CPUs. The main focus of this paper was on assessing the impact on accuracy of the resulting energies and properties, in particular in iterative schemes. The results indicate that the rate of error accumulation in single precision is sufficiently slow, and overall single precision introduces negligible errors for total energies, excitation energies, forces, and properties. Moreover, single precision can be used in geometry optimizations with analytical gradients. If tight convergence is desired (e.g. in finite-difference calculations), single precision can be used to speedup iterations in the beginning, converging to the single-precision result first and continuing in double precision. In most cases the total number of iterations is not affected and the speedup is close to the theoretical estimate.