Typical gas bills in winter?

Hi all, my partner and I have just moved into our first home in canberra together this year after both living in apartments for a while. As its an older house, it has ducted gas heating. We've just gotten our gas bill and it's much higher than we expected, and we wanted to check if this is a normal amount for an older house here? We apparantly used 33000MJ of gas throughout in the last 3 months, with it providing our hot water and ducted heating. We would only run the heating in the evenings, and turn off before bed. We don't know if this is normal, or if we potentially have a leak we'd need to look into.

Thanks