The main aim of this article is estimation of the heating energy demand and annual heating costs for classical sacral building equipped with ground source heat pump or gas boiler. For this purposes a simulation model in the Matlab Simulink 2022b has been developed. Heat losses through the building elements were analysed and elements requiring thermal insulation were indicated. According to the research, current state of the building (without thermal insulation) require 241.73 kW of peak thermal power and 227.03 MWh of thermal energy annually. Values were calculated for 107 days heating season and +12°C of internal temperature. According to the results it is possible to reduce peak power to 107.78 kW (44.5%), and energy consumption to 70.53 MWh (31.1%) in relation to primary values. Annual heating costs presented as a Variant 4 is 5 386 EUR for Ground Heat Pump and 7 071 EUR for gas heating with CO2 emission costs included. Variant 5 presents the possibility of additional reduction of maximum heating power, which affects the final cost of the installation.