Season 1 "Progress"
And apparently enough energy to heat "two hundred thousand homes". Seriously, sometimes you'd think Bajor only had like 10 million people the way they talk about it, they needed to scale up the numbers a lot.
But regardless of that, I found it disturbing that they were willing to poison the entire atmosphere of a habitable moon for some energy and on top of that, there WAS another option to use some sort of phase technobabble technology that wouldn't harm the moon but they had to wait one year. Wait on year or poison an entire moon? Hmm, tough choice...not.
When 200.000 families CAN NOT wait another year, as was clearly established, for this energy then it is the most reasonable thing to do.
Bajor JUST got out of the occupation. They didn't have the means to support themselves fully, what with their planet being raped to near death by Cardassians. Sorry for my language......
Anyway, they had not other choice, otherwise they'd condem 200.000 families. Kind of an easy choice then really.