Print Time & Power Calculator

What this calculator works out

Two inputs and one multiplication. Electricity cost is the easiest cost on a 3D print to get exactly right, because the arithmetic has no judgement in it at all:

There is no waste allowance and no failure rate here, because both of those already multiply the machine hours elsewhere. This page answers one question: what did the electricity meter move for this job?

Finding your printer's real power draw

The number on the label is the maximum the machine can pull, not what it pulls while printing. A machine rated 350 W will usually sit far below that during a PLA print, because the bed heater cycles on and off rather than running continuously.

Three ways to get a usable figure, in order of accuracy:

• Measure it. A plug-in energy monitor between the wall and the printer, read during a normal print. This is the only figure you can defend, and the meters are cheap.
• Add up the loads. Bed heater watts × its duty cycle, plus hotend watts × duty cycle, plus roughly 10 – 20 W for the board, motors and fans. For a 220 W bed cycling about 40% of the time, a 40 W hotend at about 50%, and 15 W of electronics, expect something near 150 W.
• Start from the label and halve it. Crude, but closer to reality than the nameplate. Treat the result as a placeholder until you have measured.

Enclosed printers with a heated chamber sit at the top of the range, because the chamber heater adds a continuous load. A small open bed-slinger printing PLA sits at the bottom.

Why your tariff matters more than your printer

Two people running identical machines can differ by a factor of four on this line, purely because of where they live and which tariff they are on. The table below is the same 4.3-hour, 120 W job priced at four different rates — find the row nearest your own bill rather than using anyone's national average:

Even at the top of that range, a single print is cents. The reason to include it is not that it is large — it is that it is one of the few costs you can state exactly, and it stops a long overnight run being treated as free.

Worked example: a 4.3-hour print

Print time 4.3 hours, average draw 120 W, tariff $0.30 per kWh:

Put the last two rows side by side and the point of this page becomes obvious. At a plausible machine rate, the hours are worth roughly six times the electricity. That is why the full print cost calculator asks for a machine rate and a power figure separately: they are not the same cost wearing two hats.

When the hours matter more than the kilowatt-hours

Electricity is small, but time is not, and the two behave differently as a print gets longer.

A 20-hour print does not cost much more to power than a 4-hour one — it costs five times the machine hours, five times the chance of failing overnight, and five times the plate time you cannot sell to anyone else. Restricting a long print to a cheap tariff window (overnight, or a lower-rate period) saves cents. Clearing the machine for the next paid job saves dollars.

Use this calculator for the honest, exact, small number. Use the machine-hour rate for the one that actually decides whether the job was worth running.

Important assumptions

The default 120 W and $0.30/kWh are the calculator's example values. Both are plausible and neither is measured on your machine or your bill. Change both before you use the result for anything.

The calculation assumes a constant average draw across the whole print. Real machines vary: heat-up pulls the most, the first layers with a hot bed pull more than the last ones, and a tall print with active part cooling pulls slightly more at the end. Averaging across the whole job is the right simplification for costing, but it will not match a meter reading to the cent.