Reducing My Carbon Footprint

By cycling instead of driving whenever possible, I have rediced my use of petrol by about 80%. I used to fill up my tank about once a week with 30 litres of petrol. Over a year I would use about 1560 litres of petrol. Each litre contains 32 MJ or 9 KWh of energy, so over a year I would use about 14000 KWh of energy. Now I only fill upwith 30 litres once a month. In a year I use about 360 litres of petrol containing 3240 KWh of energy.
I also have solar panels installed on my house. These panels generate about half of my electricity needs. Last year they generated 2000 KWh of electricity of the 4000 KWh I used..
I used to need about 14000+4000=18000 KWh of energy.
Now I only need 3240+2000=5240 KWh of energy from non renewable resources.
My carbon footprint has been cut by

\[\frac{18000- 5250}{18000} \simeq 71 \%\]