So I was thinking… And that’s how I get ahead of my abilities. 
The ecobee thermostat has a “thermostat heating” property which shows when the furnace is running, as in the image below. (Orange Sections)
Now of course it’s great using HA to integrate everything, and have an interface to turn things on/off… but at some point we overlook the ability of these tools to gain real insight into ways to improve our lives. So my thought process goes like this…
What if I could use the “thermostat heating” information to calculate the energy efficiency of my home in some way? I know there is 24 hours in a day, and if I could calculate the amount of time the furnace runs I could determine the percentage of time it must run based on the average daily temperature.
For example… If I use a weather sensor to create an “Average Outdoor Temperature” for the day (say 40 degrees F), and then figure out that my furnace was running for 15% of the day at that temperature, I could assume that my home was 85% efficient at 40 degrees. If the next day it’s an average of 30 degrees, and my furnace ran for 17% of the day, then my home would be 83% efficient for the day… Etc…
This type of information could be used to determine all sorts of insight into the way changes in the home affect your energy efficiency. What happens if I turn the heat down 2 degrees? What if I close off the unused bedroom door? Where is the “sweet spot” between turning the heat down vs. how efficient it is? If 1 degree doesn’t matter below 30 degrees outside, why bother being colder all day?
So do any of you have any thoughts on how to implement this? Maybe this could be used as a template to help others be more energy efficient in this uncertain energy climate we’re in right now.
Looking forward to thoughts.
Steven