Most manufacturers publish one power figure. Prusa publishes two, and the pair tells you more about print cost than either number does alone: the MK-series averages 80 W printing generic PLA at room temperature and 120 W printing generic ABS. Same printer, same motors, same electronics. The difference is almost entirely the bed working harder to hold a higher temperature against the room.
That is the single most useful fact on this page, because it means your material choice moves your electricity bill by half again — and it means any published "cost to run" figure that does not say which material it assumed is not a figure at all.
The hot plate on a cold machine
A 120 °C bed ceiling is unusual on a machine with no enclosure. It is not there so you can print ABS in the open; that combination fights physics and loses. It is there for the materials whose first layer wants heat that the ambient air will then take away — filled nylons, some polycarbonate blends, and PET-based engineering grades that adhere badly below 100 °C.
For those, a very hot plate does part of the job an enclosure would otherwise do, at the base of the part where adhesion is decided. It does nothing for the upper layers, so tall parts in those materials still curl. That asymmetry is worth knowing before you buy filament on the strength of the specification: the plate is generous, the surroundings are not.
What the S actually changed
The MK4S is a revision rather than a new machine. The substantive change was the hotend: a higher-flow melt zone and a nozzle system that swaps without tools, plus reworked part cooling. Owners of the previous revision could buy the change as a kit rather than a printer.
That upgrade-kit culture is a genuine cost factor and it belongs in a running-cost discussion. A machine that receives official hardware revisions holds resale value, and a machine you can repair with catalogued spares has a longer usable life over which to amortise its purchase price. When you set the machine-time input in the cost calculator, that input is purchase price divided by expected lifetime hours — and lifetime is exactly what a long spares supply extends.
Living with a bed-slinger at speed
The plate moves on the Y axis, and it is a large plate. Everything that follows from that is familiar to anyone who has owned this class of machine:
- Tall, narrow parts wobble. Print them near the centre and drop acceleration before you drop speed.
- Ringing appears on Y-facing surfaces first, and input shaping calibration is the fix rather than slower printing.
- A part that comes loose does not merely stop printing; it becomes a projectile inside the machine.
Against that, the direct-drive toolhead makes TPU genuinely straightforward, which no bowden machine can claim regardless of its motion system.
The nozzle is brass, and that is a choice
Stock is soft brass, so filled filaments will wear it. The tool-free swap system makes changing it a two-minute job instead of a hot-tighten ritual with a spanner, which lowers the practical barrier to keeping a hardened 0.6 mm for functional work alongside the standard 0.4. The 0.6 mm reference explains what that second nozzle actually changes; on this machine, the answer is mostly time.
The owner this machine expects
It suits people who want to understand and maintain their printer, who value published spares and documentation over a closed appliance experience, and who print a wide range of materials rather than a wide range of colours. It is a poor choice if you want a machine you never open — there are better-integrated appliances at the price — and it is the wrong shape entirely if you need a chamber, in which case the CORE One is the same manufacturer's answer and the correct one.
If your budget is the constraint rather than your preferences, the MK3S+ does most of this more slowly for considerably less on the used market, and shares much of the spares catalogue.