Energy usage has changed, a lot. No longer will your units require energy to fire. This change means that you will no longer have to worry about your army being completely unable to fire if your energy economy tanks. The energy to fire mechanism was unique and was a neat little mechanic, but the problem is that it was always simply to opaque to end users, especially newbies.
The new system implements energy costs for all structures and units except Economy structures and Builders. This means that no matter how bad your energy income is, as long as you have metal, you will always be able to grow your economy. I think that this is a nice way to mitigate the issue of being crippled when your economy is suffering. In this way, the only thing that will suffer is your ability to evolve units/structures, build attacking units/structures. Additionally it is worth noting that evolved metal extractors now have an energy upkeep.
This change has proved to be overwhelmingly positive for gameplay. The energy usage is a graduated cost from Tech 0 being nearly nothing to Tech 3 being quite a lot. This also means that you are not punished for staying on a lower tier for longer which leads to much more varied gameplay. As the game goes on, it means that you will have ever increasing needs for energy. Because higher tier units require exponentially more, you will have to keep expanding your production to keep up with demand.
There are now 3 different units for energy generation.
- Fission Generator
- Fusion Generator
- Cold Fusion Generator
No energy generator is available at Tech 0, this means that in order to begin evolves and increase your army power, you will need to get a tech facility fairly quickly, but another change is that you will get 10 base energy income from the very beginning which is plenty for Tech0 and allows you to start evolving at Tech 1 with very few delays.