I have recently added six very large production lines to my base, and they use a whole lot of loaders and since, my UPS have dropped a bit. Now, I'm not saying that it's Miniloader's fault since these lines themselves were bound to hit my UPS, but I'm wondering about the UPS-usage of the loaders, since I'd like to do some optimization.

TL;DR: If I have the choice between a loader and a normal inserter, would the inserter be less UPS-intensive or would it just not matter?

A miniloader is a belt plus at least 2 invisible inserters, possibly more depending on speed tier. If you don’t need or want the throughput of moving an entire belt, a single inserter will use less UPS.

If you do need more throughput than an inserter or two can provide, using a Miniloader can help UPS by reducing the number of belts and inserters overall. There isn’t a simple answer to your question. It depends on the setup and throughput requirements.

I see. Thank you for the clarification. Even though no simple answer exists, it already helps a lot in understanding how it works. No more using two miniloaders in a row for transferring things from one building to another I guess…

You're saying "at least" two invisible inserters depending on speed tier; does that mean that miniloaders don't benefit from the stack/inserter capacity researches, and you instead add more invisible inserters to provide the added throughput?

Yes, but only at extreme speeds, and not because of stack bonus. An inserter can only pick up 1 item per tick and some time is required to swing and drop the items, so for belts with more than 60 items/sec, it becomes necessary to use more than one inserter per belt lane.

More generally and not specific to miniloaders, inserters are always more efficient transferring inventory to inventory without belts getting involved in the middle. They don’t need to chase items on the belts, or find empty space on belts, etc. If you don’t need a belt you shouldn’t introduce one if your goal is UPS efficiency, and that includes loaders of any type.

On the third hand, this doesn’t mean you should replace long belts with inserter+chest chains, either. Since the optimizations of 0.16, long belts are merged into a single entity for UPS purposes, so they are more efficient than having lots of individual inserters. Every component has a role in play in the right circumstances.

Alright. I'm mainly using Bob's ultimate belts which are 75/s so I guess I'll reconsider how often and when I'm using the loaders. Thanks for all the explanations.