It depends on what size bottle you are going to use, the following is from the Campingaz website,
Multi-functional stove and grill (toasts)
Power: Stove = 2x 2,300 watt; Grill = 1,100 watt
Gas outflow: Stove = 2x 170g/h; Grill = 80g/h
Boil time: 6min 30sec (1 litre)
Runtime: Stove and Grill > 6h 30min; Stove > 8h on R907
Operating off Campingaz® and others’ Butane cylinders
Dimensions: L52.5 x W31 x H22cm
Weight: 5.8kg
As to the number of cooks, it depends on what you are cooking, how long things take to cook etc.
I have a camping chef and use a 13kg propane bottle, I have used the bottle with our BBQ and on camping trips and it lasted for 2 seasons.
We used to have a 1l kettle but found that the base was too small for the flame so got a bigger 2.5l kettle and ot boils quicker, and the handle no longer gets hot!
I was thinking of upgrading to the Vario Grill as it is smaller when packed away, and has the Piezo ignition but the hob is less powerful (not much though) and has better windshields.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.