To be fair, you are using up the entire resgen though to produce only 8x more power, which would then need to power other resgens to create resources to use and other machines. Yes it's infinite but resgen speed is also important. Not sure what the power limit on the creation of resgens but you do require more power per a resgen the more resgens you make.
With that said I'm looking at coal from resgen to pulverizer to magma crucible to 2 stills to compression dynamos. A quick and likely slightly inaccurate calculation in my test world suggests that a single resgen can create ~ 13000 RF/T using 16 or so compression dynamos upgraded to resonent tier with 3 auxillary transmission coils and a ignition plug. All other machines were upgraded with speed upgrades minus the specilization in the stills for better refined fuel production. Could get more RF/T using more dynamos with some efficiency upgrades. As a bonus only 1 pulverizer,1 magma crucible, and 2 stills were needed to fully max out the resgen when the machines were fully upgraded.
edit: apparently the upper limit on resource gen power creation power usage is only 1 million RF. So it probably wouldn't be that bad to create the extra generators for charcoal.