Here is an idea:
I know (and there could be an account section where I tell you) the size of each floor of my house, construction, how many windows, Roof/cavity insulation and so on.
When I input my meter readings, you know where I live and could access historical geo-accurate weather (temp) data for my location. For any degree of external temperature, there is already a known algorithm to calculate how much heating energy is required to maintain an internal temperature of, say 20C. As the external temp drops, I need to consume more energy to maintain that internal temp and vice versa.
You could then calculate an energy efficiency rating - a 0-100 scale, where 100 is for my size of house/construction with zero heat loss and at the other end, 0 is my house without a roof or doors etc.
This would mean, that every time I input a meter reading, you can give me a personalised dynamic efficiency rating, with the bounds of what should be expected in a well insulated house. I could then see (over succesive meter readings) how any extra insulation has increased my efficiency or turning off unecessary radiators etc.
You could even turn this into a commercial opportunity and offer me discounted insulation or whatever.