Google and esVolta test energy storage for time-shifting renewable energy certificates

Google, energy storage developer esVolta, and the Quintrace and LevelTen Energy platforms have completed a three-month pilot programme testing a new commercial structure for storing surplus solar energy. The project discharged stored energy, together with renewable energy certificates verified on an hourly basis, at times when Google’s electricity demand exceeded the available supply of clean energy.

Purpose of the pilot

Google funded the pilot programme to determine whether energy storage systems could be used to time-shift renewable electricity and the associated environmental attributes.

The project time-shifted a total of 9.2 GWh of electricity charged from solar generation, using two US-based esVolta energy storage systems:

• Anole – 240 MW / 480 MWh,
• Burksol – 100 MW / 200 MWh.

Together, the systems have a combined power rating of 340 MW and a storage capacity of 680 MWh. esVolta has been developing, owning and operating utility-scale battery projects in North America since 2017.

How did the mechanism work?

Google identified specific daily time windows in which electricity consumption exceeded the expected available supply of renewable energy.

esVolta charged its batteries with surplus solar generation during other hours and then discharged the stored electricity – together with the associated renewable energy certificates – precisely during the identified periods of shortfall.

Google did not pay for storage under a tolling arrangement and did not assume market or dispatch risk associated with the energy storage assets. esVolta retained full operational control of the assets, including the ability to respond to price signals or grid emergencies outside the agreed time windows.

Granular certificates

The renewable attributes used in the pilot were tracked using so-called granular certificates – a form of energy attribute certificate timestamped on an hourly basis, rather than using the monthly or annual aggregation applied in conventional energy attribute certificates.

Granular certificates are issued in accordance with a standard developed by EnergyTag, a non-profit organisation. Quintrace verified each hour of battery charging and discharging against this standard, applying loss calculations to determine how much certified renewable electricity was actually delivered after passing through the storage system.

LevelTen managed the registry accounts underlying the transactions to prevent double counting of the same renewable attributes.

First commercial structure of its kind

The companies involved described the arrangement as the first publicly documented commercial structure in which a corporate buyer enters into an agreement specifically to time-shift environmental attributes it already owns by using energy storage.

The pilot forms part of Google’s broader effort to match its electricity consumption with carbon-free energy on an hourly basis, rather than relying solely on annual net balancing.

The company is pursuing its stated goal of powering its data centres with carbon-free energy around the clock (24/7) by 2030. Google has already reported matching 100% of its annual electricity consumption with renewable energy, but on an hourly basis the figure is only around 65% – a gap the company says it aims to close through its 24/7 carbon-free energy strategy.

Uncertainty surrounding emissions accounting standards

Organisations responsible for corporate CO2 emissions accounting standards have for some time been assessing whether and how more granular concepts of matching electricity consumption with clean energy should be incorporated into their frameworks. However, neither of the two major standards relevant in this area has so far introduced a mandatory hourly matching requirement.

The SBTi Corporate Net-Zero Standard, Version 2.0, published in June, requires large electricity users – those consuming at least 10 GWh annually – to calculate and report an hourly renewable energy matching metric. This reporting requirement will become mandatory for larger companies when the standard opens for validation in February 2027. However, actually achieving a high level of hourly matching remains a separate, optional basis for recognition under the standard rather than a requirement for target validation itself.

The GHG Protocol, which sets the accounting rules used by most companies for Scope 2 emissions reporting, is also considering similar changes, but has not yet adopted a mandatory hourly matching requirement.

Public consultations on the proposed changes ran from October 2025 to January 2026 and attracted more than 1,000 responses. Only around 22% of all respondents, and approximately 12% of the companies that responded, supported making hourly matching mandatory.

Impact on the corporate energy procurement market

Uncertainty surrounding the expected revision of the standards has already been linked to a slowdown in corporate clean energy procurement – the volume of corporate PPA agreements fell by 10% in 2025 as buyers waited for greater clarity on the rules.

The GHG Protocol Standards Board has since directed its working group to develop several possible reporting approaches rather than a single mandatory rule. The revised standard is not expected to be finalised before the end of 2028.