On most of the printers profiled here, the electricity term is a curiosity: a few cents, dwarfed by plastic and machine time, worth computing only because guessing at it produces answers that are wrong by an order of magnitude in both directions. On this machine it finally becomes a line you can see.
A 420 mm open plate is the largest heated surface on this site, and it is losing heat to the room for the entire print with nothing between it and the air.
The full-plate job
900 g of filament at $19/kg, 34 hours, a 15% failure allowance, machine time at 35 cents an hour:
| Term | Amount |
|---|---|
| Filament | $17.10 |
| Electricity, 8.84 kWh | $1.55 |
| Machine time | $11.90 |
| Failure allowance | $5.39 |
| Total | $35.94 |
8.84 kilowatt-hours is a meaningful quantity of energy — comparable to running a domestic oven for several hours. It is still under a twentieth of the job's cost, which is the point this site keeps arriving at from different directions: electricity matters most as a thing people get wrong by a factor of ten, not as a thing that decides purchases.
It is the 34 hours rather than the 260 W that makes 8.84 kilowatt-hours. Halve the hours and double the watts in the cost calculator and the energy line does not move at all, which is the quickest demonstration that duration is doing the work here. If your rate is the German or Australian figure rather than the US average, that line roughly doubles and the conclusion does not change.
The wattage is estimated, not metered. It is derived from bed area, bed voltage and enclosure on comparable machines. On a printer this unusual, that estimate carries more uncertainty than it would on a mainstream 220 mm machine, and if you own one and have put a meter on it, your figure beats this one.
What 420 × 420 × 480 is actually for
Very few people need this, and the ones who do need it badly:
- Cosplay armour and helmets in one piece rather than four, which removes the seam work entirely.
- Full-size functional parts — car interior panels, machine guards, furniture components.
- Production batching, where thirty small parts on one plate is a completely different economic proposition from three plates of ten.
The third of those is the strongest argument and the least discussed. A large plate's real value is often not one large object but many small ones, because machine time is charged per plate rather than per part.
The costs that are not on the bill
Preheat time. A plate this size takes a long time to reach temperature, and during that time the machine draws hard and produces nothing. On a 34-hour job that is noise; on a 40-minute job it is a significant fraction of the total.
Levelling. A 420 mm plate is very difficult to keep flat, which is why machines this size use dense probe meshes. Probe hot, and re-probe when the seasons change — this is not superstition, it is a plate with a large thermal expansion taking a different shape at 60 °C than at 20.
Floor space and mass. This is furniture, not a desk appliance.
Risk concentration. A failure at hour 30 on a 900 g part is a genuinely expensive event, which is why the failure allowance above is set where it is rather than at the optimistic single digits smaller machines can justify.
Materials, and the warping problem at scale
An open frame at this width makes high-shrinkage materials a poor idea rather than a difficult one. Warping force grows with the distance from a part's centre, so a 400 mm ABS panel concentrates enormous peeling force at its corners. PLA and PETG are the honest material list here, with filled versions of both for stiffness.
If a large part in ABS or ASA is specifically what you need, the answer is an enclosed large-format machine, not this one with a tent over it.
Big prints fail slowly, and quietly
Long prints on a big open plate fail in slow, undramatic ways. A corner lifts imperceptibly at hour four and the part is detaching mid-print by hour twenty. A slightly under-tensioned belt produces layer shifting that is invisible until the part is measured. Neither announces itself, and both argue for watching the first hour of a print you intend to leave for a day.
Why most people should size down
If your parts fit in 300 mm, they should. The step from 300 to 420 costs desk space, preheat time, levelling effort and running cost, and buys area you may use once a year. If your interest is height rather than footprint, the CR-10 Smart Pro reaches nearly as high in a much smaller machine. And if you want big parts in warping materials, buy the enclosure with the printer, not afterwards.