Utility electrical meter - 31,172kwh
Utility electrical meter shows 31,172kWh today.
2014-03-28 meter was 27,148kWh.
robert@debian:~$ timediff 2014-03-28 2015-01-16
294 (days)
robert@debian:~$ echo $((31172 - 27148))
4024 (kWh)
4014/294 = 13.69kWh/day = 570watts/hr