It won't be too much trouble to calculate. Energy consumption is now calculated at constant prices in 2005. In other words, you take the GDP in 2005 as the base period and multiply it by the GDP growth rate in 06, 07, 08 and 09. Because the official GDP growth rate is constant, you can get the constant GDP in recent years, which can be used as the denominator.
It will be more troublesome to make energy consumption data for a longer time. The data calculated by the same method is comparable and meaningful, but the value of the data itself will not be officially recognized.
In addition, many yearbooks now have unit energy consumption and decline, why do you want to calculate it yourself?