How much has average gas consumption increased in the period 2009-2010 compared to 2008-2009 (after the severe winter)?

Answer

Dear Joeri,

You ask a very good question.

As you yourself mentioned, there is a relationship between the course of the outside temperature and gas consumption for heating. How cold a winter or a year is is scientifically expressed in “degree days” relative to a reference temperature. In Belgium, this reference is taken at 16.5°C. (more info on http://www.synergrid.be/index.cfm?PageID=17601)

If you want to keep the temperature constant in a house during a cold winter, you will use more gas for heating than in a “mild” winter. You can roughly say that the number of degree days increases in line (linearly) with the consumption of your heating installation.

On a day with 0 degree days (average outside temperature > 16.5) you normally (almost) do not have to heat, while on a day with many degree days you will burn a lot.

How are those degree days determined?

On a day when the outside temperature averaged 0°C, you say that day had “16.5 degree days”. On another winter day, when the average outside temperature is -10°C, you say that day had 26.5 degree days (16.5 – (- 10)).

If the average temperature is higher than 16.5°C, the number of degree days for that day is by definition = 0. If you add up all these degree days of the whole winter (or the whole year), you have a measure of the “severity of winter. For the period 2008-2009 (July – July) this sum was 2350, for 2009-2010 this sum was 2380 degree days.

In Belgium, the average number of degree days (over the last 30 years) is 2415. Although there were some very cold days during the winter of 2008-2009, these two winters do not have many degree days and both were (over a year) still relatively mild winters, with approximately comparable expected average gas consumption.

PS: in addition to the theoretical method, you could also view the actual state of affairs, based on the numbers of the gas suppliers: this naturally includes the increase in the number of connections.