@Luna. There are many viable businesses whose core service is energy-modeling. I don't know that any of these businesses generate millions and millions of dollars, but they are self-sustaining. At the same time, other businesses struggle. There are many variables.

Location is important. Energy modelers do better where the economy is healthy, there is moderate construction activity, and there are energy-efficiency codes and beyond-code programs that encourage efficiency.

Target clientele is also important. You mention ESCOs. There are enough poorly performing buildings out there that ESCOs can focus on low-hanging measures that don't require modeling to either plan or to clear a deemed-savings threshold. Energy modeling is primarily a new construction tool at this point, although hopefully that will change in the future as deeper energy efficiency becomes more prevalent.

As with any business, experience and connections are important. It often helps to work in an established business where you can build your portfolio and gain some exposure before striking out on your own.

There is no single right answer, just some general rules of thumb. Putting my DOE hat on for 30 seconds, we recognize the situation and are trying to develop tools (like EnergyPlus and OpenStudio which you are already using) and resources (like UnmetHours :)) that help modelers deliver high-quality services at lower costs. But it's an ongoing process.</rant>