When is “green power” accepted as zero-carbon under standards like EN 15804 (EPD), the GHG Protocol, ISO 14064-1, and ISO 14067?

This is a very important question. For "green power" to be accepted with a zero or reduced CO₂ emission factor under standards like EPD (EN 15804), UN GHG Protocol, ISO 14064-1, and ISO 14067, it must meet specific requirements:

The electricity must be backed by valid Energy Attribute Certificates (EACs) such as GOs, RECs, or I-RECs. These certificates must be properly tracked, retired, and matched to the period and location of electricity use. Without this proof, the use of green power may not be accepted in product carbon footprints or organizational reporting.

For example, in Environmental Product Declarations (EPDs) under EN 15804, green electricity can only be used with a zero factor if it's contractually proven and allocated to the specific product system. If this isn’t clearly documented, the default grid emission factor must be used.

In short, green power is only accepted with a low or zero CO₂ factor when there is clear evidence of certificate retirement and proper allocation. Without this, the purchase may not be recognized in verified reporting — which can lead to cost without real attribution in your carbon footprint.