Hydrogen and electricity may become the favoured twin energy carriers in a possible ＇＇greenhouse driven＇＇ future due to their lack of CO2-emissions at the point of use. It is shown that decarbonising fossil fuels to hydrogen with CO2 being stored in deep geological formations represents the least expensive way of producing CO2-free hydrogen. For fossil fuels there seems to be a natural progression from fuel switching (coal to oil to natural gas) for low to moderate emission reduction pressure. For increasing pressure for reduction of emissions CO2-free (decarbonised) electricity from coal will be introduced followed by decarbonised electricity from natural gas and decarbonised hydrogen from natural gas.