Let's see: the 9300 is quoted at 26W max, and the price of electricity is about 15p/kWh.
26W x 24h = 0.624kWh/day = 9.36p/day = £34.19/year.
Turn it off for 18 hours a day and save (at most) £26 per annum, with the inconvenience of having to reset all your recording schedule each time, or get a new PVR that pays for itself in about four years.