Hi rob987,
Thanks for all your help
Thank you for the very thorough first post!
The kWh value is only really used to display "daily usage" of 15 - 30 kWh. It could be read every 15 - 30 minutes.
Another possibility I forgot to mention would be using a scripting data source to enable, wait, and then disable the points that don't need the faster poll rate, and then speed up the polling on the data source normally.