... "meter readings"... how come this sounds so very familiar to me...? 
Anyhow, Abbas: You ask too much for what you tell us.
We don't know your data model.
We don't know how your analytic view looks like.
We don't know your base data.
We don't know the expected output.
If you're not able to provide a small reduced version of your problem and post the desired SQL code to recreate a working example, then I'm sorry, I won't look at the problem.
Of course I could guess like everybody else what precisely you want as an output, but that's inefficient!
Instead, boil the problem down, show us your base data and your expected output - THEN I'll have a look (or maybe others as well).
- Lars