I'm fairly sure that the total economic value that we get out of roads far exceeds the cost it takes to create and maintain them, yes. A similar argument can probably be made for justice systems and armies.
If a power generation system costs more to operate than the value of power we get out of it, it's probably not very useful. I think that's what we're talking about here.
Notice how for roads you compare the total economic value of all roads against the cost of them. But for electricity you compare a single power generation system. You are not comparing the same thing. A fair comparison would be the total economic value of having electricity against the cost of all electricity infrastructure. Sadly this fair comparison is irrelevant in this thread.
I think that for your analogy to work, you also need to consider the total economic value that we get out of electricity as opposed to just revenue from electricity bills...?
If a power generation system costs more to operate than the value of power we get out of it, it's probably not very useful. I think that's what we're talking about here.