When assessing energy savings, the use of math is not a substitute to engineering common sense.
Math is an enhancement tool: if engineer has made in error – math will not correct it; math will make it bigger.
Never mind calculations, statistical analysis or even artificial intelligence, if result does not make engineering sense – look for an error.
Always check if your results make sense.
Following this simple rule helped me avoid embarrassment of presenting client with savings that exceeded total consumption. A seemingly small error may have a catastrophic effect, not only to project, but to your reputation.