Hiya,
While setting up a new ship, I ended up with Power Produced reading as 127.00 and Power Consumed as 127.00 but both were still showing red. I was able to save and use the design (and watch it turn into pretty chunks of debris 
)
The setup was as follows
Imperial Legion Cruiser Hull
Multiple Warhead Missiles * 5
Guidance Scrambler Beam * 1
Fast Recharge Shields * 6
ECM Shield * 1
Cruiser Engine 3 * 1
Crew Module 3 * 1
Power Generator 3 * 1
Power Generator 2 * 1
Cheers