Original Prusa MK4S: problems, parts and running costs
Checked: 2026-10-10
Summary
Most owner complaints come down to money: the MK4S costs more than Bambu Lab and Creality rivals, its high-flow nozzle wastes filament in MMU3 multi-material work, and the open frame means ABS, ASA, HIPS and PA need a separate enclosure. Running costs are filament and replacement print sheets, which are consumables outside warranty except for delivery defects. At Prusa’s $925 direct price (2026-10-10) it is a fair-to-good buy; at or under $800 it is strong value.
Common problems and fixes
- Print quality affected by speed — TechRadar lists it as a reason to avoid, worst at the top of the speed range; the workaround is staying off maximum speed; not a defect, so warranty does not apply. [2]
- Open frame limits ABS, ASA, HIPS and PA — these materials print best inside an enclosure that is a separate purchase; plan for the extra cost if they are the point of the machine; not a defect. [1][2][3]
- High-flow nozzle wastes filament in MMU3 work — Prusa recommends the standard nozzle when the MMU3 multi-material unit is in use, because the high-flow CHT nozzle increases filament waste during changes; swap the nozzle. [1]
- Print sheets are consumables outside warranty — the PEI spring steel sheets are not covered except for defects on delivery; replacements come from Prusa’s e-shop, so budget for them. [1]
- Reported retirement — Tom’s Hardware reported the MK4S would be retired once stock ran out; as of the 2026-10-10 check Prusa lists it in stock at $925, so availability may tighten. [1][3]
Parts and consumables
- High-flow Prusa Nozzle brass CHT, 0.4 mm (made with Bondtech) — standard fitment; owners swap to the standard nozzle for MMU3 work, and everything comes apart with Allen keys. [1]
- MMU3 multi-material unit — optional add-on that runs five filaments and swaps them in 25–35 seconds; listed at about $359 on Prusa’s e-shop category page in the 2026-10-10 check, not re-verified. [1]
Yearly running cost
Not enough data. No research file reports a typical owner’s yearly spend on this printer. What the files do establish: ongoing costs are filament and replacement print sheets [1]; the assembled printer ships with 1 kg of Galaxy Black Prusament PLA [1][3]; and the printer draws about 80 W on PLA settings and about 120 W on ABS [1], so electricity is a minor part of the bill.
When it is a good buy
Prusa e-shop, 2026-10-10: assembled MK4S $925, kit $657.40, in stock with one to three business days of preparation [1]. That is down from the $1,099 launch retail and $999 Prusa price reported in August 2024 [3]. Value bands from the research: at or under $800 it is strong value for a repairable, independently tested open-frame printer; at $925 directly from Prusa it is fair-to-good; above $1,100 value is weak unless you need Prusa’s upgrade path or already own an MK4.
- Prusa CORE One — CNET’s “Best 3D printer for accuracy” pick in its 2026-07-27 roundup; the better choice if you want Prusa accuracy without the open frame. [4]