Source Energy represents the total raw energy consumed at power plants and extraction points required to deliver energy to a building, including generation losses and transmission inefficiencies. This metric accounts for the full supply chain from fossil fuel extraction through final delivery to the building meter. Source energy is typically 2.5 to 3.5 times higher than site energy for electricity-dependent buildings.
Technical Details
Source energy calculations convert site electricity consumption using regional grid efficiency factors (averaging 33% nationwide). Natural gas remains relatively unchanged as a source fuel since most gas reaches buildings directly. The conversion factor from site to source energy varies by utility region and generation fuel mix. Buildings in coal-heavy regions have higher conversion factors (3.5+) than those serviced by renewable-heavy grids (2.5).
Applications and Significance
Building energy codes and LEED certification require source energy analysis to reflect true environmental impact. Source Energy metrics encourage efficient equipment selection and renewable energy adoption by showing the complete energy lifecycle. This approach incentivizes on-site solar and wind systems that reduce grid dependence and avoid transmission losses, potentially improving overall efficiency by 15-30% compared to grid-only strategies.