Omegatron also did away with a set of cascading pie charts on Wikipedia, a particularly ineffective use of this chart type. Whenever there are more than two or three categories, the necessary use of many colors can really make one's head spin.
Here, the cascade is being used like a log scale, to artificially elevate the small pieces, which unfortunately are also the least significant pieces of the energy pie. There is no reason for nuclear, bio-mass, hydro and "others" to add to 100% except that the author decides to group them together. The 41% nuclear or the 41% solar heating in the second and third charts, respectively, have no meaning in the larger context.
In deference to the original author, Omegatron's new version preserves the arbitrary three-level cascade. He converts to stacked bar charts, which brings out the differences better.
He also sensibly exposes the original proportions rather than the arbitrary relative proportions. For example, nuclear energy accounts for 6% of the total, not 41% of the arbitrary "others" bucket which in turn contains 14% of the total.
I'd prefer an even cleaner presentation with unstacked bar charts. This can be done in either one chart with all eleven categories, or in two charts, as shown below. The two-chart version assumes that the reader have two key questions: alternative energy sources as a proportion of the total, and the mix of different sources within the alternative category.
With the ordinary bar chart, many fewer colors are needed, and there is no need to print out each data point, nor a need to use guides to point to labels and data. The trouble of the latter is its tendency to draw attention to the least important aspects of the data.
With this further example, I continue to find the Wikipedia rule to discourage text annotations on graphs bewildering. Such a rule apparently does not apply to data labels, as can be seen here. Of course, a graph without any labeling of categories is robbed of meaning but if labels can be saved, so should annotations!