Having power units is great, but if your regen is sub-par than while you can cloak, it'd only last moments. And while your shields may regenerate fast, it would suck your power dry to do so. While you may have the biggest gun ever made, you'd only be able to fire it for about 2 seconds.
Doing anything with your ship takes power. Flying, cloaking, shooting, shielding. Using anything has a drain on your power source, which has its own cap of 20,000 units. This can be extended by adding Power Tanks, but that doesn't help too much if your regeneration rate is in the toilet.
Ship power regeneration is calculated by not just the amount of Power Cubes, but how you place them. If you make a solid 5x5x5 cube, you won't peak regeneration at all. At the same time, if you make 3-D "L" and "T" shapes, you get more regeneration for your space and blocks. This is broken down in various pages and videos, the one I found most useful is This One, which I used as a base recipie to modify into my own design, a 9x9x9 cube filled with Power Cubes and Shields . I was running with Power Tanks instead, but their optimization is in solid cubed format instead of scattered, compared to Shields which really don't care how they're placed. The basic idea is to have long strings of Power Cubes to maximize regeneration output per blocks used. Now, this may not be the most efficient design in the world, but it works rather well for its size.This is the first layer, of 9x9x9. Ignore the green diamonds, that's just my station in the distance. The blue/green cubs are the power cubes, and the white/gold cubes are shields.
Notice how many of the power cubes don't continue into the second layer, but not all. Some threaded through most of the design.
The third layer, these were all created using the X-Y-X axis' mirroring, ensuring they remained symmetrical.
The fourth layer in the design. Nearing the middle, the design on the sides match the first and last, as it is a perfect cube of 6 corners.
The fifth, and middle slice of the cube. If you were building this power configuration on a X-Y-Z perfect mirror, the middle here would actually be your starting point, From here until the last slice, it is a repeat of the first 4 in opposite order.
Slice number six, a duplicate of slice number four.
Piece seven, looks a lot like piece three...
Almost done. Number eight, a clone of number two.
And the ninth and last slice of the optimal 9x9x9 power cube, its pattern should now be reflected on all six sides of the entire cube.
Finally, the finished cube itself. Notice its power regeneration, at 50723 units per second! You can ignore the shielding number unless you really want to make this as your base of a frigate-class shielded.... thing...
Again, this may not be the absolute perfect power generation answer. This is what I found from expanding on a 5x5x5 to make it X-Y-Z symmectrical. Please, comment your thoughts on the matter!