> The burner inserter is the most basic and slowest type of inserters. It is powered by burning fuel, compared to the more advanced inserters which are powered by electricity. It will add fuel to its own supply if it picks any up, which makes it useful for filling boilers with coal. This has the advantage that it will continue working even if the power fails, as opposed to electrically-powered inserters which will be unable to function.

In particular, when power demand drops below the supply everything starts running slower, which in turn means that the electrical inserters used to feed coal into the boilers run slower which drops the rate of electrical production. Burner inserters don't have that problem.

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Schmitt triggers are really easy with stock multi combinators now. It isn't so much a "things have issue with flickering power" but rather "turn off the coal feed to the steel furnaces that would go to the electrical station instead" and "make sure that the coal unloading station doesn't brown out" and "turn off power to the electrical furnaces and labs to make sure that the coal mines don't dip in production rate when power dims".

The Schmitt trigger also makes for more reasonable "where is there excess oil that I should produce solid fuel from?" There's the optimal, but sometimes in the processing you can't crack any more crude to gas because the heavy oil is backed up, so turn on the appropriate cracking station when {conditions} and turn it off when {conditions}.