I would like to see if my pollution cloud is growing or shrinking, so it would be useful to see how much pollution is being generated in total, and how much is being absorbed in total.

How about attaching an operational cost (other than electricity) to using bots instead?
I didn't fully work the idea out yet, just throwing it out there.
Perhaps some system of inserting fresh batteries in "used up" robots? Maybe the roboport needs to be fed with batteries in order to recharge the ...

I originally posted because I was stuck with the implementation, not the higher level idea of how things should work.

Why being concerned with fuel usage? Because, like most people who play Factorio, I want things to be as optimized as possible.

After fiddling around a bit with it, I came up with ...

I would like my entire base to run on nuclear power, my power setup is scaled to deal with the highest expected load (currently 2 nuclear reactors is enough).
However, I do not like that the energy from the reactor is wasted if not all energy is used. To remedy this, I added storage tanks that store ...