Power

At T1 community fusion stations are present, ending the dependency upon dirty atomic energy.
At T2 fusion reactors are portable, but not personal/man-portable. Think car engine sized or larger. Beamed energy is also reality, and given the reduction in energy requirements of most electronic devices, very effective
At T3 XHC-D Cells (aka Excellsiors) - extra high capacity with near dimensional storage - are a reality. Unless you’re powering an entire complex for a couple of years, the only other thing they’re good for is heavy energy weapons, large vehicles, or limited personal shields. The batteries require a portable fusion reactor to charge them (though it’s not like just plugging in your laptop - these things take quite a draw to charge them properly!). Fortunately, they are very stable and - with the exceptions of the noted usages - last a pretty long time.
T4 sees the theoretical arrival of personal fusion cells (literally: just add water) and Zero Cells (Zero Point Cells) - batteries with more theoretical than actual existence, and yet they provide power… from somewhere. Zero Cells still need to be recharged from powerful sources, but they make energy based weapons very practical and powerful... and small. Also, the use of anti-matter and similar wierd energy sources are possible.