With cars, most people are familiar with the MPG (miles per gallon) rating system to determine their efficiency. Passive House standard captures performance of a building in a similar way by limiting the amount of energy used per square foot of living space in one year.
This means instead of MPGs, a building’s performance is measured in British Thermal Units or BTUs per square foot of finished interior space and year, or kWh per square meter and year in the metric system. The maximum allowed is 4,746 BTUs per square foot and year, or 15kWh per square meter and year in the metric system.
Passive House standard also limits the amount of primary energy used to make the energy consumed in and by the building.