Although the renewable hydrogen that will be produced in Europe over the next few years is often in the news for its potential new uses (hydrogen cars, electricity production and storage, etc.), it is necessary to first decarbonize its current uses. In fact, 8.7 million tonnes of hydrogen were already being consumed in Europe in 2020, 82% of it by just two industries: oil refining and the production of ammonia, the main compound used in the manufacture of nitrogen fertilizers. Since 91% of European hydrogen production capacity runs on natural gas, hydrogen production emitted over 80 million tonnes of CO2 in 2020, or 2.5% of EU-27 emissions. Replacing this hydrogen with low-carbon hydrogen would considerably reduce these emissions. In addition to the technological and industrial challenges, low-carbon hydrogen production must also become economically competitive, so that today's consumers can rapidly decarbonize their activities. This report, which complements the two previously published, looks at the influence of various economic factors on the difference between the production cost of low-carbon hydrogen and that of fossil hydrogen.