By Zac Bloom, Vice President, Head of Sustainability and Renewables and Sandy Beauregard, Director of Sustainability Services
The Greenhouse Gas Protocol (GHG Protocol) is undergoing the most significant revision to Scope 2 accounting standards since the release of the original Scope 2 Guidance in 2015. The proposed revisions aim to improve the accuracy and credibility of greenhouse gas accounting and emissions reduction claims. One major change that has been proposed is the introduction of hourly matching and deliverability requirements for renewable energy certificates (RECs) and other energy attribute certificates (EACs) used under the market-based accounting method.
For renewable energy buyers, the practical takeaway is straightforward: if hourly matching becomes part of Scope 2 accounting, annual REC procurement will no longer be enough to support a 100% renewable electricity claim. Buyers will need to evaluate when renewable generation occurs, whether it is deliverable to the relevant load, and how much additional cost is required to close the remaining hourly gaps.
Under current GHG accounting standards, organizations can reduce Scope 2 emissions by matching their annual electricity consumption with an equivalent annual quantity of RECs. With this approach, a company can purchase enough RECs on an annual basis to report zero market-based Scope 2 emissions, even if the renewable electricity was generated at times that did not coincide with the organization’s load. In response to criticism that this annual matching does not accurately reflect actual electricity consumption patterns driving emissions, the proposed changes seek to establish a stronger temporal relationship between renewable generation and electricity use.
An immediate concern with hourly matching is that most REC and EAC markets do not yet operate with hourly certificate issuance at scale. Hourly matching would also require more granular electricity-use data than many organizations currently have, increasing the burden for metering, data management, and verification. To address these concerns, the proposed framework would allow organizations to use load profiles to approximate hourly electricity use and renewable generation data.
Response to Hourly Matching Proposal
The Greenhouse Gas Protocol solicited input on the proposed changes and published a summary of feedback received on July 29, 2026. Of 909 organizations providing feedback on the hourly matching requirement, 70% indicated no/low support for the proposal. The most common reasons for concern are that the requirement for hourly matching would discourage participation in voluntary EAC markets, would create undue costs and burdens for reporters, and would not meaningfully improve GHG inventory accuracy.
The solicited feedback identified several potential compromises for hourly matching. Most frequently, respondents said it should be optional rather than required. Others conditioned their support for hourly matching on exemptions for small and medium enterprises or specific sites with low annual electricity use. Another suggested compromise would recognize regional differences in grid infrastructure, EAC registries, and market maturity by implementing a phased approach or linking the requirement to readiness criteria.
What Hourly Matching Means in Practice
For organizations in New England, hourly matching would fundamentally change how renewable procurement strategies are designed. Rather than matching total annual electricity use with total annual renewable generation, organizations would need renewable generation or qualified attributes available during each hour of electricity consumption. Any hour without sufficient matching renewable generation would require residual emissions factors or another accounting treatment specified in the final guidance, making 100% renewable electricity or zero Scope 2 claims much harder to support.
To illustrate the implications of hourly matching, consider a hypothetical Massachusetts college with 17,000 MWh of annual electricity consumption. This load level is representative of many private colleges and smaller universities in the northeast. Under today’s Scope 2 market-based accounting rules, the college could purchase 17,000 voluntary RECs annually and report zero market-based Scope 2 emissions. Under a future hourly matching framework, the question becomes much more complex. How many of the college’s 8,760 hours of electricity consumption are actually matched by renewable generation that occurs in the same hour?
One of the largest challenges in New England is the pronounced seasonal variation in both electricity demand and renewable generation. Electricity consumption often peaks during hot summer afternoons driven by air conditioning load and on cold winter mornings and evenings driven by heating-related electricity demand and lighting.
Solar production is highest during spring and summer and falls significantly during winter months. There is no generation overnight, and cloud cover can create significant hourly variability. A solar project that appears sufficient on an annual basis provides far less support during high-demand winter periods. Wind typically performs better during winter but remains highly variable, with output that can fall well below expected levels for hours or days at a time and sometimes across broad geographic regions. While wind improves coverage because it can generate outside daylight hours, it cannot reliably satisfy every hour of a 24/7 load profile. There are many hours when renewable generation and load profiles are poorly aligned, so how could this Massachusetts college achieve 100% renewable electricity under hourly matching requirements?
The following scenarios are illustrative and intended to show directional impacts rather than prescribe a single procurement strategy. Actual results would depend on the buyer’s hourly load shape, resource location, certificate eligibility, contract pricing, transmission and deliverability rules, and the final Scope 2 standard.
Scenario A: Solar-Only Procurement
Suppose the college signs a virtual PPA for a Massachusetts or New England solar project producing approximately 17,000 MWh annually. Under current accounting standards, the college is fully covered because annual renewable generation equals annual electricity consumption. However, when viewed on an hourly basis, academic buildings continue to consume electricity around the clock while the solar does not generate overnight, provides limited generation during winter mornings and evenings, and cloudy days create prolonged generation shortfalls.
In Table 1, modeling shows that a 12.5 MW solar array can meet 100% of the college’s annual load, but only 47% on an hourly basis. This approach, which meets current GHG accounting standards but falls significantly short when considering hourly matching, costs $543,000 per year. Increasing the project size to 20 MW (Scenario A1) would meet 160% of the college’s load on an annual basis but is still only able to match 49% hourly. This 2% increase in hourly matching costs an additional $325,000 per year, bringing the annual cost to $869,000 while still leaving more than half of hourly consumption unmatched. While solar-only procurement has been a common strategy for meeting emissions and renewable goals, additional generation sources are needed under hourly matching requirements.
Scenario B: Wind-Only Procurement
Now assume the college contracts with a 6.8 MW wind project producing 17,000 MWh annually. Wind performs better than solar because it generates electricity during more hours of the day and generally provides stronger winter and shoulder-season production. Modeling shows this project covers 100% of the college’s annual load but aligns with only 53% of campus load on an hourly basis, at an annual cost of approximately $475,000. The challenge is prolonged for low-wind periods. For example, a January weather event could combine elevated campus demand with several consecutive days of low wind output, leaving significant consumption unmatched. Increasing the project size to 15 MW (Scenario B1) generates 220% of the college’s annual electricity, but only 68% on an hourly basis. Under this scenario, the college would purchase more than double the annual RECs needed at a cost of over $1 million while still falling well short of 100% hourly matching.
Scenario C: Wind + Solar Portfolio
A more realistic future strategy would require diversification. Assume the college contracts for 4.75 MW of solar and 4.2 MW of wind. The annual total remains 17,000 MWh while the hourly matching benefits from complementary generation patterns. Solar contributes primarily to summer afternoons, daytime academic building loads, and air-conditioning season demand. Wind contributes to evening hours and nights, shoulder seasons, and winter.
As seen in Table 1, combining wind and solar significantly improves coverage without increasing the total procurement volumes. For our college, hourly coverage improves from 47-49% with solar alone or 53-68% with wind alone to 68% with a diversified wind-solar portfolio. This is achieved with an estimated cost of approximately $500,000 per year, lower than a comparable solar-only strategy and approximately $25,000 per year higher than the wind-only strategy achieving a 53% hourly match.
If the wind and solar offtake is increased to 10 MW each, the portfolio is able to achieve 82% hourly matching. However, this again would require purchasing more than double the amount of renewable electricity needed on an annual basis and drives the total cost over $1.1 million annually.
Scenario D: Wind + Solar + Hydro Portfolio
A particularly important scenario for New England institutions involves the addition of hydroelectric resources. Hydro can provide higher availability and better alignment with constrained hours than intermittent solar and wind resources. In this scenario, the college would need to contract with 3 MW of solar, 3.5 MW of wind, and 1.15 MW of hydro to meet its annual electricity consumption. However, this portfolio still provides only 74% hourly matching. Even when the portfolio is expanded to cover 133%, 164%, and 191% of annual load, hourly matching still falls short of 100%, reaching only 89-91%, while total annual cost surpasses $1.14 million.
Scenario E: Storage
Battery storage can help address temporal misalignment, but it is not a complete solution to hourly matching. Solar and wind generation often occur when electricity demand is lower than renewable output. Storage can shift excess renewable generation into later hours when demand exceeds production, improving hourly matching over short periods. It cannot, however, create renewable energy during extended periods when renewable output is low.
Assume the college installs a 2 MW/8 MWh battery with solar. The battery can store excess midday solar generation and discharge it into the evening, helping bridge the gap between solar production and campus load. Without storage, any excess generation is effectively wasted from an hourly matching perspective. With storage, the excess energy can be shifted to the 5 PM-8 PM period, when solar production is low but campus electricity loads remain high. This improves hourly matching performance.
Storage can also improve the effectiveness of wind resources. Although wind generates during both day and night, output remains highly variable. Batteries can help smooth short-duration fluctuations and increase the percentage of hourly load that is matched with renewable generation. However, storage becomes less effective during prolonged multi-day periods of low wind production because battery systems eventually become depleted.
Consider a cold January week with minimal solar production, multiple low-wind days, and high campus electricity demand. An 8-MWh battery would be discharged rapidly. If insufficient renewable energy is available to recharge the battery, storage provides little benefit beyond the first day. The largest challenge is not necessarily shifting solar from noon to 6 PM but supplying renewable energy during winter mornings and evenings or during multi-day low-renewable events. Batteries are able to solve the hourly shifting issue but cannot solve seasonal renewable shortfalls. These periods require resource diversity rather than storage alone.
Conclusion
If hourly matching becomes the new standard, the corporate renewable procurement market will shift from annual energy accounting to portfolio optimization. Organizations that currently report zero market-based Scope 2 emissions through annual REC purchases may find that only a portion of their actual electricity consumption is matched by renewable generation in the same hour.
The most resilient future strategy is likely to require detailed hourly load analysis, diverse renewable resources, and strategic deployment of storage. The requirement for hourly matching will drive costs and the size of projects needed to meet existing emissions reduction goals. Even a diversified renewables portfolio that provides more than 2x the amount of electricity needed on an annual basis, is unable to match 100% of load on an hourly basis while annual costs also increase by more than 2x. The law of diminishing returns tells us that costs will only continue to increase rapidly as organizations chase the final 10% needed to achieve 100% carbon-free electricity under hourly matching requirements.
Given this, one of the most important strategic questions is whether organizations should move forward with renewable contracts before the final rules are implemented. The GHG Protocol has indicated that contracts executed under existing Scope 2 rules may be grandfathered under future guidance, although the exact treatment depends on the final standard and has not yet been finalized.
For organizations with significant electricity consumption, there may be advantages to acting sooner rather than later as existing procurement structures are well understood, and REC markets continue to operate under current rules. There are several long-term contract opportunities available today and future demand for hourly-matched resources could increase prices after the updates are finalized. However, organizations should recognize that the specifics of any grandfathering provisions remain subject to the final Scope 2 standard.
Alongside the published feedback on the proposed updates, the GHG Protocol announced that it and the International Organization for Standardization (ISO) would combine their GHG accounting standards into a single global accounting standard. This partnership changes the standard development process and further extends the timeline for a new standard to be published. ISO and the GHG Protocol now expect to release a draft standard for review in the second quarter of 2027 and the final standard by the end of 2028.
With the timeline extended, limited information about grandfathering, and low support for mandatory hourly matching in the GHG Protocol feedback, organizations should not wait for certainty before acting on near-term emissions reduction targets. They should continue to take meaningful action aligned with internal policies and current greenhouse gas accounting standards, while considering diversified renewable portfolios and longer-term contracts that may remain valuable under a range of future Scope 2 outcomes.
Photo by: Simon Skafar