That problem has been solved. A bit over a year ago NIF was able to produce about 3MJ of energy with about 2MJ of input.

This particular experiment didn’t do that but that likely wasn’t the goal… They managed a 69MJ output over five seconds… the NIF experiment was less power but over “a few billionths of a second”.

69MJ over five seconds is 13MW which is a very usable amount of power. About on par with the typical output of a real world utility power generator, compared to the old one which was similar to a small lightning strike - impressive but not useful. It’s not enough to power an entire city, but you kinda don’t want that anyway since a city should have redundancy. Several 13MW generators could power a city with enough excess production to take one or two of them offline for maintenance. If you combined this with solar/wind(*), you could have two or three fusion reactors for a large city.

The tech is still not ready of course, but it’s getting closer and seems to be accelerating too - those two breakthroughs were a year apart. This generator is right in the sweet spot, now they just need to improve efficiency / reliability / reduce costs.

(* I seriously doubt fusion is ever going to be cheaper than solar / wind / hydro - but it could be more reliable making it a great “baseload” option - enough to keep the lights on, fridges cool, etc)