It's hard to wrap your head around the amount of number crunching that goes into energy analysis, and how to prioritize your time and effort when working on a project. There are energy modelling tools that can be used that make it easier, but in a lot of cases, the easier the modelling tool is to use, and the less actual, real-world performance testing data you input, the more likely the result will be a ball-park figure that doesn't relate to actual energy usage, or actual heating or cooling loads.
