The United States has a long-term goal to reduce 50% of energy usage in buildings based on 2010 consumption levels. Home energy efficiency is often measured by laboratory experiments and computational simulation. Thus, there is little to no quantifiable evidence showing the extent of energy efficiency homes can achieve within the larger context of green building standards. The objective of this research is to identify actual home energy performance as an effect of green building technologies by comparing energy use from real-world observations and energy modeling. Results indicate a significant reduction of energy consumption at 43.7% per unit or 43.4% per square foot (i.e., 0.093 m 2) and substantial financial savings at $628.4 per unit or $0.80 per square foot (i.e., $8.6 per m 2) annually. Savings account for 2% of median annual household income or 46% of energy cost expenditures for an American home. Results also identify the construction type as a significant factor, yet building technology is not the only factor influencing a home's energy efficiency. The findings contribute to the body of knowledge in three aspects: (1) simulated energy usage is higher than actual energy usage; (2) energy modeling via simulation tools is particularly accurate for new construction; and (3) energy modeling, especially for existing buildings, is not accurate due to largely varying occupant behaviors.