Nuclear power technology is heavily restricted in this day and age by GDI forces, and they guard the MCV plans for their power plants jealously - other than Nod's independent development of the technology, the world is for the most part incapable of duplicating the power output or efficiency of nod or GDI power plants. The Forgotten, working with this fact, created the solar panel system, a power generation technology capable of converting light into energy, and, using principles derived from current MCV matter-energy conversion technology, created the Solar Array power system.
While the Solar panel system was still not as efficient or reliable as GDI or Nod power plants, it was capable of producing roughly half the power of the GDI and Nod Nuclear plants - a feat not duplicable by most modern nations. The Solar panel system, despite it's success, is nowhere near as useful, efficient, or cost-effective as GDI or Nod Nuclear plants - Fortunately, the Forgotten have adapted to this limitation, using a mixture of Cost-efficient power rationing - made easier by the simple and easy-to-manufacture technology the Forgotten prefer - and smaller Solar systems capable of partially self-powering certain Forgotten structures - to cut power consumption on their base structures considerably. As a result, even a single solar array is able to power multiple buildings for the Forgotten indefinitely.