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.