Operating processes of open-type sorption heat accumulator in heating systems were studied. The al-gorithm for calculation of its performance is developed. It includes computation of mass transfer cofficient, sorp-tion, useful heat sorption, heat input for heating the sorbent, device casing, water in the humidifier, evaporation of water, heating the sorbed water, desorption, and calculating efficiency coefficient. Operational performance of open-type heat storage device based on the sorbent composite ‘silica - sodium sulfate’ is estimated. Suggested com-posite sorbent is obtained from tetraethoxysilane, Na2SO4, ethanol (as a solvent), hydrochloric acid (as a catalyst) and polyionenes served as organic modifiers. The impact of vapor flow velocity on efficiency is taken into account by the coefficient equal sorption value. A monotonic increase of efficiency coefficient while increasing the vapor flow speed and its relative humidity is shown. The efficiency coefficient of heat storage device is shown to be with little to no dependence with regeneration temperature heightened from 90 ºC to 110ºC. The optimal operating con-ditions of the heat accumulating device which allow to operate with maximum magnitudes of efficiency coefficients 53 – 57 % are stated to be vapor-air mixture speed 0.6 - 0.8 m/s and relative humidity of 40 – 60 %. The results of simulative experiments and field trials are given. Field tests were carried out in two modes differed with start time. Heat storage device was switched on in the morning or in the evening for load-factoring of electric energy peaks, indoor temperature being kept within limits from 20 ºС to 22ºС during day or night hours. Correlation between effi-ciency coefficients deduced from experiments and calculated with suggested algorithm is confirmed. The possibility of reducing the power consumption by applying of the heat accumulators in 2,4 - 90 times versus decentralized heat-ing systems on basis of solid fuel boiler, gas boiler and electric boiler is stated when open-type sorptive heat stor-age device used. Results of the study can be applied to develop sorptive storage devices in decentralized heat supply and ventilation systems and sorption units for utilization of low-temperature waste heat.