Cost-plus rate structure means the monopoly makes more money when they choose more expensive generation methods:

Cost plus means that the monopoly can charge us for the cost of a project (spread out over years) plus a set percent for profit.  Usually that percentage is set around 8-10 percent.  That means if they have a choice of building two different 100 megawatt plants, one for 200 million or the other for 400 million, they will make an extra 16 million off of ratepayers if they choose the more expensive option.  And not only would we be out that extra 16 million, but we would also be out the total difference in cost.  In this scenario that means we pay and extra 216 million.  That is probably why in their last resource plan, they chose not to fully consider tax credits that could reduce their costs (and our bills) by more than 50%.