Gas usage query.? my sister and her partner have have a HUGE gas bill, i...

my sister and her partner have have a HUGE gas bill, i cant remember how much its for now but they enjoy checked the bill and the units it say theyve used against their meter readings and it seem correct but they cannot work out why theyve used so many unit. they live in a small, 1bedroom flat, built contained by the last 10 years, next to a modern instant hot water boiler, which runs the middle heating, and a gas cooker. they simply use the heating for a couple hours surrounded by the evening, and hardly at adjectives during summer but the units they appear to be using is more than even my mum uses - she's at home adjectives day, uses the heat much more as well as cooking beside gas, and is in a 3bedroom house, which is at most minuscule 3 times the size of my sisters flat.

Im looking for suggestions as to why they could be getting through so many unit of gas each month, if anyone can imagine of any.
Incense cross-examine?
Answers:    Call the gas company for an inspection of your gas connections.
Can I store my freezer without risk within...
Maybe she's cooking up meth.