How does a 2.4 kW electrical heater compare to running the gas central heating for a 4-bedroom house?

I have a 2400 W Delonghi electrical heater in my bedroom that I use quite often - usually on the 1 setting [rather than the 2 setting]. My mum thinks that it would be cheaper to put the central heating on for the whole 4-bedroom house than running my small heater! I doubt this very much, but what kind of consumption [in kWh] does an average gas central heating system use up? And is it a lot more than my small heater?