I've just uploaded a new Indigo Web Server plugin called the Device Usage Report that provides a rudimentary device usage report. It should give you a good idea of how many minutes a day the devices in your house are ON. You could use this data, in conjunction with something like a Kill A Watt (for plugin devices anyway) to figure out how much power is being used. But mainly, it gives you a clue about what devices in your house you may want to target for bulb replacement, auto-off triggers, etc.
Note, this plugin relies on a couple of things:
• SQLite must be configured properly and SQL logging enabled. Since it uses the logging data provided by SQL logging, it will only report data since you enables SQL logging - so a blank report most likely means that you didn't have SQL logging enabled for that day.
• For the most accurate reporting, devices should really be 2-way so if they are manually operated Indigo will see the change. All INSTEON devices of interest are 2-way, but only some X10 devices are.
Also note: only devices that were actually used during the day show up.