What to remember from this promise is that a construction of a new nuclear plant will begin… in some form.
That is, not necessarily a physical nuclear plant, it can just as well be only a permit to make one. It’s a nice way to say ‘Hey we began the process of a new reactor!’ without having to go back on his words if there won’t be an actual construction start before the election.
On the contrary it will be very expensive for the tax payers and only pay off if the energy price is above some certain price, which it probably wont since renewable energy has given Sweden negative energy prices recently, and most certainly will continue to do. And if that’s the case, the state has to pay the reactor owner the difference instead.