A dielectric insulation medium including a hydrofluoro monoether, the hydrofluoro monoether containing at least three carbon atoms. The insulation medium according has high insulation capabilities, in particular a high dielectric strength, and at the same time a low GWP. The invention further includes an insulation medium which is chemically and thermally stable also at temperatures above 140° C., which is non-toxic or has a low toxicity level, and which in addition is non-corrosive and non-explosive.