More than 21m homes in the UK alone depend on natural gas for heating and/or cooking. Replacing that infrastructure with zero-carbon solutions would result in a remarkable large-scale effort. For the sake of argument, say it takes 8 person-days to replace the gas heating infrastructure in a home with something that is zero carbon. That is about triple the time it takes to install a new gas boiler and would result in 150m days of work to physically do the replacement or about 1 million years of work. This alone could create 200,000 highly skilled installation jobs for five years, let alone the ancillary roles around it.