The postwar period is a crucial time for the course of many industries, not the least of which is energy. Immediately following the war, with coal and oil gone and the last reserves of natural gas dwindling, solar and wind power explodes. Geothermal and tidal energy become extremely prevalent. Hydropower and nuclear power supplement these industries. The fall of Big Energy has allowed individual families to create their own solar panels to power their homes without interference from giant corporations. Personal robots housing picofabricators build the panels for their human masters. Engineering Cooperatives design blueprints for more efficient panels and wind turbines, selling the prints at a very reasonable cost.
A century or two after the war, fusion power finally arrives. Fusion plants replace fission plants, as well as most geothermal, wind, solar, tidal, and hydro plants. While solar remains a major power source for individual homes, cities slowly become more reliant on fusion power. The fourfold power increase from fission to fusion allows for experiments and projects requiring higher levels of energy, and scientists begin exploring the possibilities of post-fusion era.
The most promising of these is the antimatter power plant, capable of energies 300 times more powerful than fusion. While it may take researchers decades, perhaps centuries, after the advent of fusion energy to make antimatter reactors practical, the new power plants will come online before the beginning of the next millennium. The antimatter reactors give humanity the power boost it needs to perform experiments that result in the discovery of new sources of even more powerful energy. Even after the discovery of such power, it will be even longer, on the scale of millennia, before humanity discovers the power source it needs to make wormholes and Retrieval realistic. However, just as wood made way for coal, which made way for oil, which made way for fission, which will make way for fusion and so on, so too will our road to even greater energies continue. The day will come when we find a way to harness dark energy itself, which will allow us to truly break free of time's grip. Of course, this is assuming dark energy and time are connected. But I'll get to that...