The present invention relates to an electrically heatable packed pressure-bearing apparatus for conducting endothermic reactions having an upper (3), middle (1) and lower (3) apparatus section, where at least one pair of electrodes (4, 5) in a vertical arrangement is installed in the middle section (1) and all electrodes are disposed in an electrically conductive solid-state packing (26), the upper and lower apparatus sections have a specific conductivity of 105 S/m to 108 S/m, and the middle apparatus section is electrically insulated against the solid-state packing, wherein the upper and lower apparatus sections are electrically insulated from the middle apparatus section, the upper electrode is connected via the upper apparatus section and the lower electrodes via the lower apparatus section or the electrodes are each connected via one or more connecting elements (10, 16) that are in electrical contact with these sections and the ratio of the cross-sectional areas of the upper and lower electrode to the cross-sectional area of the respective current-conducting connecting element or, without use of a connecting element, the ratio of the cross-sectional area of the upper and lower electrode to the cross-sectional area of the respective current-conducting apparatus section is 0.1 to 10.