My TiVo uses 27 Watt during boot and 24 Watt when running normally. It doesn't appear to use any less power when in standby mode (my low cost Electricity Usage Monitor only measures to the nearest Watt). This may seem like a lot of power but my previous "Digital Crystal" PVR consumed 33 Watt.
The Minimum Energy Performance Standard (MEPS) proposed for simple Digital Set Top Boxes is 1 W in passive standby and 8 W On mode. For Pay TV and Other STBs (which would cover the TiVo) the standard is 1 W in passive standby and 15 W Active Standby. There is no level set for power use when on for STBs with hard disks.
On a generous interpretation the TiVo would meet the standard as it doesn't have a standby mode: it is always recording programs. A less generous interpretation is that it has an Active Standby which is 60% over the standard.