McKinsey put together this cost-benefit chart of greenhouse gas abatement methods. The width of each box is the estimated impact in reducing greenhouse gases, the height is the estimated cost. So everything below the line saves money as well as reducing greenhouse gases. I assume this takes initial capital investment into account. Here's the text of the study.

There are usually hidden costs to technology changes, and political dimensions that make purely technocratic analysis like this less than a slam-dunk. Framing the discussion around relative cost-benefit data is a good place to start, though. There are a zillion initiatives that might make sense individually, but that shouldn't be near the top of the list of priorities. These initiatives will appear as congressional earmarks - the green economy will be a political economy. We need people in the discussion nudging us back to the highest carbon ROI investments.