When designing organic ferromagnets in nano- and bio-systems, it is essential to account for solvent effects as most biological reactions occur in water. The minimized mixing elongation (MMELG) method was combined with the polarizable continuum model (PCM) for accurate and efficient electronic structure calculations of the lowest and highest spin states of huge systems with solvent effects. The MMELG-PCM-L-min method that combined the MMELG-PCM method and the L-min method can be efficiently and reliably applied to predict the high spin ground state stability of conjugated organic polyradicals and is thus useful for designing organic ferromagnets with solvent effects. (C) 2015 Elsevier B.V. All rights reserved.