What is the difference between capital cost (CAPEX) and operating cost (OPEX)?

Capital cost (CAPEX) is the one-time investment to build the facility: equipment purchase, installation, piping, instrumentation, civil/structural, electrical, buildings, and project services (engineering, construction management). Operating cost (OPEX) is ongoing expense to run the plant: raw materials, utilities (steam, power, cooling water), labor, maintenance, catalysts and chemicals, and overhead. Design decisions affect both: larger equipment increases CAPEX but may reduce OPEX (better efficiency). Total cost evaluation uses: payback period, NPV (net present value), or IRR (internal rate of return) to balance CAPEX and OPEX over project life.