The gas consumption of a gas fired gas heater depends on:

• what temperature will we set on the thermostat. The thermostat is adjustable between + 13 ° C and 33 ° C
• what is the heat transfer coefficient of the heated room
• the number of heating hours, i.e. whether we heat the room 24/7 or only 8 hours a day on working days, e.g. an office

Sample gas consumption for a 5 kW gas convector in a moderately insulated room (10 cm of polystyrene + 40 cm of brick). The room is an office which is used 8 hours a day. The comfort temperature is 20 ° C, the night temperature is 8 ° C. Consumption during 20C comfort temperature and convector operation 30% of the time for 8 hours a day. Consumption 0.39 kg / h * 8 h * 0.3 = 0.93 kg. The remaining 16 hours during night temperature and convector operation 10% of the time for 16 hours. Consumption 0.39 kg / h * 16 h * 0.1 = 0.62 kg. So the convector will consume 1.55 kg daily. 

The above example is very approximate and consumption may vary depending on the factors mentioned above.