Printer power draw × print time × price per kWh.
Official: the manufacturer's average draw while printing PLA. Measured: an independent lab measurement. Estimate: no per-model figure is published, so it is set by printer size and type. ABS and other high-temperature materials draw more; for the most accurate number, measure your printer with a smart plug.
Every printing hour wears the printer: nozzles, build plate, belts and maintenance. Count it so your price covers it.
