Operational Carbon
Operational carbon is the greenhouse-gas emissions from running a building once it is built — heating, cooling, hot water, lighting, plug loads, and any natural gas, propane, or oil consumed on site. It is measured in kilograms of CO2-equivalent per year and is separate from embodied carbon (the emissions from materials and construction). For a code-built home, operational carbon dominates lifetime emissions; for a Passive House on a clean grid, embodied carbon may be larger over a 50-year horizon.