AbstractPublically available data is presented comparing recent historical daily energy flows through Great Britain's electrical and gas transmission networks with a focus on domestic heat and hot water. When this data is expressed graphically it illustrates important differences in the characteristics of the gas and electricity demand; these include the quantity of energy delivered through the networks on a daily basis, the scale of variability in the gas demand over multiple timescales (seasonal, weekly and daily) and the relative stability and predictability of the electrical demand. As the United Kingdom proceeds to migrate heating demands to the electrical network in its drive to cut carbon emissions, electrical demand will increase, but equally importantly the variability and uncertainty shown in the gas demand will also migrate to the electrical demand, which suggests both technical challenges and opportunities for management of future energy networks.