Mine electrical power-flow solutions are often obtained using personal computers. Because of the limited precision used by the compilers on these machines, power-flow solution procedures may diverge or possibly oscillate until the iteration limit is reached, even though an operable solution exists. Two methods to create virtually extended-precision calculations in full Newton-Raphson and decoupled power-flow algorithms without the attendant slow down associated with full double-precision codes are presented. It is shown that insufficient precision for convergence of the IEEE 118 bus system occurs near the single precision limit of a PC- or VAX-class minicomputer, the number of bits required for convergence can be simply and quickly estimated, and the most critical routine in which precision generally needs to be increased is the mismatch routine. Simulation results are discussed.