Over the past 18 months, I've kept a record, pretty much every minute, of my electricity usage. I bought an EDF energy monitor, then used the data-cable to link it up to my home PC to catalogue the data that it's been producing.
Though there's an overhead in running some electricity to find out what my electricity consumption figure are, the results have been quite exciting. I've yet to really dig deep into the statistics, but have been using Google Charts to play around with the stats to work out what the most efficient combinations are to use the least electricity in my house.
I have the advantage that the entire house runs off electricity, and with only a few hours of downtime in the last 18 months, I've now got a useful dataset to play with. I'm now writing a simple API to pull the data out in a way that makes sense to me, and will be consuming that data with Google Charts and D3JS to do year-on-year comparisons & more granular data analysis.
So far this year though, even with the simple graph I have here at http://uth.zrmt.com/electricity.php we've managed to save approx 15% on our electricity bills through fine-tuning the water heater and underfoot heating to behave in the most energy-efficient way. I'd love to take this further and start developing on top of this.
If anyone's interested in helping consume the data, please get in touch and I'll give you access to a simple API. If you also have an EDF energy meter, I'll also pass on instructions to get the program setup to start cataloguing your own home electricity usage.