To obtain LEED Zero Energy certification, a project must achieve a source energy use balance of zero for the past year. The net zero energy balance is based on the quantity of source energy delivered and the quantity of renewable energy that displaces non-renewable energy on the grid. Renewable energy generated and used on site reduces the amount of energy delivered. Source Energy Balance = (Total Source Energy Delivered) – (Total Non-Renewable Source Energy Displaced) This equation can also be written as:
Source energy balance
=(total energy delivered x nonrenewable source conversion factor)
-((total renewable energy generated and exported to grid
x nonrenewable source conversion factor)
+(offsite renewable energy procured
x nonrenewable source conversion factor))
To calculate source energy delivered to the project, use the national average ENERGY STAR Source-Site Ratios for each building energy source from the Energy Star Portfolio Manager Technical Reference: Source Energy for projects in the U.S. and Canada. International projects may use the U.S. source-to-site ratios or published source-to-site ratios for the country or multi-country region where the project is located. Use the same source energy conversion factors for calculating energy delivered and non-renewable energy displaced. Environmental benefits of all renewable energy generation or procurement must be retained by the project.
Table 1. Source Energy Balance
If purchasing Energy Attribute Certificates (EACs), also known as Renewable Energy Certificates (RECs), the EACs must be Green-e Energy certified or equivalent. Carbon offsets must be Green-e Climate certified or equivalent.
Projects must purchase EACs annually during the three-year period when the certification is valid. On-site renewable energy generation and consumption will vary based on weather and operating conditions, so year to year the required purchase will vary. For LEED Zero certification review, it is sufficient for the project owner to provide a written commitment to purchase EACs each year during the three-year period when the certification is valid in order to maintain the net zero source energy balance.