Decreasing of gas usage
During the years, the gas usage decreased, it could be that they improved the efficiency over time.
Switching to another energy provider
The cost of energy is pretty consistent from 1999 to 2006, then gradually increases and there is only one year when it drops, they probably switched to the new provider in 2006, and the new provider has difficulties in keeping a stable price, for some reasons, it also has much more variance as we can see from the second plot.
Lower water use toilet
We can notice that the average water consumption decreases over time and especially it drops in 2007-2008, where they probably changed the toilet.
Decreasing in Energy consumption
From the suggested plot for all the Junes of each year, we can see that sometimes they are correlated. There are two spikes around 2002 and 2006 in both lines. At some point, the energy consumption decreases, portentially due to more energy efficient technologies such as LED bulbs.