Average age != average service life though, so what you are essentially saying is: Service life is something above 20 years[1] The main thing about the electri

Average age != average service life though, so what you are essentially saying is: Service life is something above 20 years[1] The main thing about the electricity grid isn't so much that we need new capacity (that we actually have the production capacity to deal with), but that it changes the load distribution of the grid. And we have no (effective) way to communicate the load condition. If we could dynamically increase and decrease the consumption, then we could deal with building less excess capacity. At least here in Germany, if you look outside you'll see nearly every new house having a complete array of solar panels and all of the currently added installations come with the option to redirect the power into local storage. This isn't widely deployed yet as battery capacity is still too expensive, but within the next couple of years this will be fixed and all of these buildings will "disappear" from the electric grid. They will (largely [2]) feed themselves and all remaining demand will be time-insensitive due to the available local storage. These houses (and the associated EVs) will not put additional strain on the grid. And, if we manage to sort out the regulatory things and implement a reasonable user-interface, they may even take strain from the grid. This is a rather long story for saying this: Don't equate "capacity added" with "production increase" with "actual amount of electric energy generated and consumed". The first to numbers differ by a load factor and the last one will (increasingly) diverge, due to net-metering and friends. [1] assuming that all cars large the same time and none get "lost" by being in accidents or exported you'd get to 24 years if the half-life is 12, in practice I would assume a certain heavy-tailness and a peak somewhere around 20 [2] most houses will be _heavily_ oversupplied on a year-long basis, but will be consumers to the grid for shorter periods.