My BI box sits around ~36W with Intel hardware acceleration enabled, CPU is ~24% with 6 3MP Hik @ 15fps, direct to disc. This works out to be ~$40 per year with my local power monopoly.
This is NOT including the POE switch.
Lenovo TS140 E3-1225 V3 - Intel HD P4600 - Intel C226 chipset - 12GB ECC...