A little necro posting but what the heck.
Glen, did you ever finish your shop? I built a 16' x 22' (minus ~8" on both those dimensions for actual floor space) with 12' walls. I'm now ready to run power and 240V w/30A is plenty if I keep it as a shed in it's current state, if I haul the crap out and haul my shop up there, 100A would be far more desireable to run more than 1 thing at a time. A mezzanine about 9' off the back wall will give me 6'6" of head room and not much upstairs but plenty for storage. My uncle has promised me a 24KBTU mini split he'll no longer need for his shop remodel into a 1st floor master. I've also run PVC conduit under the slab from where I'm certain I would place the jointer & tablesaw to under the wall though I've yet to bust the 1/2" of concrete covering those.
I'm struggling with how bad I want to use that as my shop knowing to just maintain the temperature & combat humidity will cost 4-5x as much/mo as the room A/C I've already purchased for the garage. Backing my truck to the garage to unload lumber & materials is now quite easy, that requires driving across the lawn if the shed becomes the shop and would be impossible when it's wet without destroying the turf. I've already purchased everything to run 30A power up there, additionally pulling 100A up there would add ~$1300 on top of my current investment. It's not yet insulated, I want to do that only after I have a better vision of what that will be used for, really a question of when moreso than if at this point.
Anyone else planning, currently building or have recently built a dedicated shop? This seems like as good a place as any to detail planning, construction and 20/20 hindsight changes that would have been undertaken differently.