That is huge, heating with gas seems to be very very common, on the order of 50% of all households use it, or about 460TWh per year. The electricity production

That is huge, heating with gas seems to be very very common, on the order of 50% of all households use it, or about 460TWh per year. The electricity production is 580 TWh per year, so its a sizeable proportion of that. Now heatpumps are efficent so not sure how much electricity will be needed, but it will be a lot.