The electrical conductivity σ and the relative permittivity (κ) as function of temperature 300 K < T < 400 K are measured and presented for potassium hydrogen carbonate KHCO3. It seems likely that the compound undergoes tow structural phase transitions at ≈ 318 and ≈ 365 K. The differential thermal analysis DTA and the thermogravimetric analysis TGA are performed in the same temperature range. The thermogram confirms the existence of structural phase transitions, whereas TGA indicates the absence of any loss in weight. The data are correlated to the crystal structure and the arrangement of the molecules in the crystal including the hydrogen bonding dimers (HCO3).