said by PhoenixDown:
(granted, meter readings will include my hot water, stove, dryer, etc that the NEST and other thermostats would not).
Other uses besides for a furnace aren't seasonal. Their consumption of fuel is generally consistent throughout the year with only minor fluctuations. Incoming water temperature does change so it will require more natural gas to heat the water to the desired temp, but it doesn't have the same extreme fluctuations that air temperature has.
Unless conditions change that require a significant changes in household activity (e.g. kid comes home from college, cooking for more people, doing a lot more laundry, etc) the month to month gas usage is fairly constant.