The cost of operating a 3D printer will vary depending on the type and size of the machine, as well as the cost of electricity in your area. In general, however, it may cost between $0.05 and $0.25 per hour to operate a 3D printer. It entirely depends on the power consumption of the machine and your cost per kw/h for electricity.
For example – if your printer draws 200w while printing:
200w x 24 hours = 4800w OR 4.8kw/h
4.8kwh x $0.3 per kwh = $1.44 per day