Need some rules to guide our project

We are now working on the Energy Efficiency Program for Progress Energy. We are having hard time figuring out what should we do to create new business model for the Progress Energy that will encourage their customers to use less energy without affecting Progress Energy's revenue. Since the only product that Progress Energy has is electricity, if we do anything that lead to people to use energy wisely or less, Progress Energy will end up having low return for their company. An analogy is like GM or Toyota encourage people to carpool and not buying a car because it will produce pollution to the world. This idea is very contradict to each other. We need to serve two stake holders who have completely opposite incentive, one is to make more money from selling energy, another is to sell less energy as possible.
With the question that we were asked, there is plenty of solutions for the case such as new price structure, adding smart grid technology, incentive program, etc. However, these seem to be hard to justify whether or not it is a good solution to the company or not. Since we haven't had any criteria or rules to measure them. So it come back to where we were in the classroom last week. When there is a creativity work, in this case to create a new business model, it will be a tough job if we don't have any limitation or measurement system that works. Working on the project like this will make you feel lost in space or in the case it can be your own thought because whatever you think seems to work but we don't know exactly that it work or not.
In order to success in this project, we as a team may have to set up some criteria that will work with the project such as revenue target, decrease in energy use per year, investment capital, technology. I believe that after we set up more concrete constraints, they will enable up to be creative without having to worry about validation of the idea