Shouldn't there be some normalization based on population? Like some of the low population states / siberia have bad emissions but that should have much less effect than a smaller difference in a more populated location.
It's an electricity map, not am emissions map. Otherwise you would have to also factor in the industrialization of the country and its imports & exports.
A good map is simple. This shows one measure very clearly. Adding another dimension would likely make the core purpose harder to interpret.
There is an age old adage "All maps lie" - which is basically another way of saying simplification is key to useful presentation. ...aerial photos aren't very useful for navigation!