I was bored enough to actually make a note of the fuel flow figures yesterday:
TOW around 26,000kg (so cruise weight around 25.5 ish), FL240, can’t remember the exact ISA deviation, but it was quite unremarkable.
At Vmo – 10 (around 245KIAS / 350KTAS) with FADEC in climb mode, total FF was 1180kg/hr. With FADEC selected to cruise it reduced to 1120. Reducing to Vmo-20 typically reduces FF to just over 1 tonne/hr, and 900kg/hr is quite achievable if you go on an economy run.
Fuel consumption on the Q400 seems to be remarkably consistent. It’s not unusual to fly the exact same route twice in the space of a few hours, and for the burns to within 10 or 15kg of each other.