For running heat pumps and charging EVs most countries have to triple their generation of electric power. I don't think any country is able to do this in just a few years.
While I've seen numbers like 250% increase in electrical consumption (assuming 100% electric vehicles and 100% heat pumps for heating) for UK that has poorly insulated houses, this will probably vary a lot between countries.
E.g. in Finland, where we don't use gas and not much coal, and have properly insulated houses, we have already over 20% heat pumps in residential homes and a bit more electrical heating, which will of course lessen the demand when switched to heat pumps (ongoing as we speak). There is also a large part with biomass and biofuels, e.g. wood, pellets and to some extent biogas. These types would probably not switch to heat pumps. We already use electricity for cooking (never used gas here), so that won't change. The bigger impact here might be electric cars.
Finland has for many years had to import electricity, e.g. typically about 10% from Russia (which has now naturally stopped) and more from the other Nordic countries. It is expected that next year we will break even for the first time, due to a new nuclear reactor and increasing wind and solar installations (told recently by national grid CEO).