A method for determining the draw-off quantity on a hot water storage apparatus comprising at least one storage tank , in or on which at least one electric heating element and a temperature sensor are disposed and connected to an electronic control device for controlling the temperature of the hot water stored in the storage tank , wherein the water temperature is controlled by activating and deactivating the electric heating element , wherein a time period Δt M of a measurement interval M i between two or more successive activations or deactivations of the electric heating element is measured via the electronic control device ; characterised in that - a heat quantity differential ΔQ i as the difference of the heat quantity Q H supplied by the heating element and the heat loss quantity Qv delivered to the environment is calculated for the measurement interval M i , wherein the heat loss quantity Qv is calculated from a design-inherent thermal resistance and the temperature differential between the water temperature θ inside the storage tank measured via the temperature sensor and the ambient temperature θ amb ; - a water quantity indicator value corresponding to or proportional to the draw-off quantity delivered by the hot water storage apparatus in the measurement interval M i is assigned to the heat quantity differential ΔQ i , and - the water quantity indicator values of the successive measurement intervals M i are summed. wherein a time period Δt M of a measurement interval M i between two or more successive activations or deactivations of the electric heating element is measured via the electronic control device ; characterised in that - a heat quantity differential ΔQ i as the difference of the heat quantity Q H supplied by the heating element and the heat loss quantity Qv delivered to the environment is calculated for the measurement interval M i , wherein the heat loss quantity Qv is calculated from a design-inherent thermal resistance and the temperature differential between the water temperature θ inside the storage tank measured via the temperature sensor and the ambient temperature θ amb ; - a water quantity indicator value corresponding to or proportional to the draw-off quantity delivered by the hot water storage apparatus in the measurement interval M i is assigned to the heat quantity differential ΔQ i , and - the water quantity indicator values of the successive measurement intervals M i are summed. - a heat quantity differential ΔQ i as the difference of the heat quantity Q H supplied by the heating element and the heat loss quantity Qv delivered to the environment is calculated for the measurement interval M i , wherein the heat loss quantity Qv is calculated from a design-inherent thermal resistance and the temperature differential between the water temperature θ inside the storage tank measured via the temperature sensor and the ambient temperature θ amb ; - a water quantity indicator value corresponding to or proportional to the draw-off quantity delivered by the hot water storage apparatus in the measurement interval M i is assigned to the heat quantity differential ΔQ i , and - the water quantity indicator values of the successive measurement intervals M i are summed. <EOS>