Years and tens if not hundreds of billions; the Netherlands is experiencing this, after a decade of cheap solar, a rise in EV, and new builds being built fully electric on the consumer side, and many datacenters and green energy generators built on the business side, our grid is at capacity to the point where new businesses can't get connected and new housing projects are put on hold (I think); the grid can't manage any more. The grid manager Tennet spent 15 billion last year, and will need to keep doing that for at least another decade - and that's a relatively small country.