The International Energy Agency has joined industry calls to overhaul the way companies purchase renewable energy to meet their climate targets, and promotes hourly certification of renewable electricity, it said.
Companies and organizations face pressure amid greenwashing accusations as they make net-zero commitments and pledge to use more renewable energy.
In a recent report supported by Google, the IEA said that the way in which companies meet targets can significantly affect actual emissions reductions.
The current annual accounting favored by most corporates would "not deliver all the technologies that will be needed as power systems decarbonize and reach higher renewables integration phases," the IEA said.
Changing settlement periods to hourly from annual would lead to more emissions reduction and encourage a wider portfolio of green technologies, the report found.
"While having clear merits, annual matching can lead to discrepancies in the emissions that a company effectively reduces compared with those for which it is responsible, linked to the fact that solar and wind are variable and uncertain," the IEA said.
Energy Attribution Certificates (EAC), which are typically annual, is the most common approach taken by corporates. However, a debate about making those more time and location specific -- which industry players call granularity -- has already been raging.
In Europe, tradeable certificates known as Guarantees or Origin (GO) are issued for renewable energy production. Discussion on the idea of granularity has risen among market players there since August, when ENTSO-E, the organization that joins together system operators across Europe, said it supported the change.
The European Parliament has also been pushing for hourly matching of GOs, and some change could come as the EU negotiates its third flagship Renewable Energy Directive due by the end of 2022.
In addition to certificates that have been widely used by corporates so far, the IEA suggests there should be a range of options, including on-site generation, power purchase agreements and green tariffs.
Some companies, it said, opted for PPAs as long-term commitments could more clearly support the financing of new renewables. But, as PPAs are not suitable for all corporates, especially smaller players, the IEA welcomed the use of green energy tariffs and certificates.
The issuing of certificates for energy produced by existing plants, a common argument against their use, was not necessarily a negative, it said.
"If the EAC market brings reliable value to existing plants, this expected revenue stream could also help secure financing for new plants. EACs are also an important mechanism in that they may be the only option for some smaller buyers that do not have access to green tariffs and lack the profile to enter into a long-term PPA," the IEA said.