The society KlimAktiv gemeinnützige Gesellschaft zur Förderung des Klimaschutzes GmbH conceived the calculator’s original version. It associates user simplicity, reliability and relative accuracy. That’s why the WWF Germany, the German Federal Office of the Environment and several German cities and Landers (Fribourg-in-Brisgau, Bavaria, etc.) use it. Esu-services provides the Swiss emissions factors which correspond to the most recent estimations of the Federal Office of the Environment (Entwicklung der weltweiten Umweltasuwirkungen der Schweiz, Bafu, 2014).