Method of determining a calorific value of a methane-containing fuel gas including one or more gas constituents in its gas composition, comprising (i) feeding a sensor unit comprising a multitude of component sensors with the fuel gas, wherein different component sensors react with different sensitivity to the same gas constituent and/or the same component sensor reacts with different sensitivity to different concentrations of a respectively identical gas constituent in the gas composition; wherein the component sensors are designed as differently composed and/or doped semiconductor sensors that are differently activated by UV irradiation and/or IR irradiation and/or microscale heating and are subject to a measurable change in resistance as a result of the presence of reducing or oxidizing gas constituents, (ii) detecting the respective change in resistance as sensor signal which is dependent on the gas composition and/or the concentration of one or more gas constituents; (iii) generating an actual gas characteristics pattern that represents each component sensor and the respective sensor signal therefrom; (iv) determining a closest target gas characteristics pattern from a group of target gas characteristics patterns; (v) extracting the gas composition and/or the concentration of one or more gas constituents from the closest target gas characteristics pattern or by interpolation from multiple target gas characteristics patterns; (vi) determining the current calorific value of the fuel gas from the closest target gas characteristics pattern rather than by analytical calculation by comparison of the actual gas characteristics pattern given by the sensor unit with the closest target gas characteristics pattern or by interpolation from multiple target gas characteristics patterns. (i) feeding a sensor unit comprising a multitude of component sensors with the fuel gas, wherein different component sensors react with different sensitivity to the same gas constituent and/or the same component sensor reacts with different sensitivity to different concentrations of a respectively identical gas constituent in the gas composition; wherein the component sensors are designed as differently composed and/or doped semiconductor sensors that are differently activated by UV irradiation and/or IR irradiation and/or microscale heating and are subject to a measurable change in resistance as a result of the presence of reducing or oxidizing gas constituents, (ii) detecting the respective change in resistance as sensor signal which is dependent on the gas composition and/or the concentration of one or more gas constituents; (iii) generating an actual gas characteristics pattern that represents each component sensor and the respective sensor signal therefrom; (iv) determining a closest target gas characteristics pattern from a group of target gas characteristics patterns; (v) extracting the gas composition and/or the concentration of one or more gas constituents from the closest target gas characteristics pattern or by interpolation from multiple target gas characteristics patterns; (vi) determining the current calorific value of the fuel gas from the closest target gas characteristics pattern rather than by analytical calculation by comparison of the actual gas characteristics pattern given by the sensor unit with the closest target gas characteristics pattern or by interpolation from multiple target gas characteristics patterns. <EOS>