With the Greenhouse Gas Protocol's public comment period now underway, the tool provides corporate stakeholders with straightforward answers on how newly proposed Scope 2 accounting guidelines will directly affect their renewable energy claims.

BOSTON and OAKLAND, Calif., Dec. 1, 2025 /PRNewswire-PRWeb/ -- Environmental tech nonprofit WattTime and REsurety, leading provider of software, services, and marketplace solutions empowering the future of energy, today launched a free, easy-to-use Scope 2 accounting calculator. With the tool, companies can see how their reported and real-world Scope 2 greenhouse gas (GHG) emissions totals would compare under the hourly matching framework recently proposed by the Greenhouse Gas Protocol (GHGP) and an impact accounting approach like the one recommended by its Technical Working Group Consequential Subgroup. It also shows the cost implications for achieving higher emissions reductions under either framework.

The tool provides critical insights and much-needed clarity as corporate clean energy buyers and other key decision makers engage in the GHGP's public comment period, which closes on December 19, 2025.

The core GHGP Scope 2 public proposal includes a local-only hourly matching requirement for inventory accounting, along with a separate proposal for reporting non-supply chain actions using an impact (consequential) approach. These revised guidelines are expected to change not only how organizations report on their emissions, but also incentivize different procurement behaviors as companies attempt to reach ambitious clean energy and climate goals.

Today, however, these proposed guidelines remain largely theoretical to most organizations. Stakeholders need a clear and comprehensive understanding of how GHGP Scope 2 changes will directly affect them. WattTime and REsurety created this carbon calculator to fill that gap. In addition, they designed the tool to look beyond what is included in the GHGP's public consultation for voluntary impact accounting — which only looks at clean energy procurement — to calculate the impact of all activity, including power consumption, to better enable target setting and tracking.

"With the Greenhouse Gas Protocol's Scope 2 public comment period underway, and on the heels of COP30, this tool is coming at a critical moment," said Gavin McCormick, founder and executive director at WattTime. "Our hope is that it helps drive the conversations companies are already having about how they can make the biggest possible climate difference, anchored by facts and tailored to their priorities."

With an impact accounting framework based on comparing induced and avoided emissions, companies track the additional emissions reductions that result from their portfolio investments, making decisions based on the most impactful times and places to generate, procure, and consume electricity.

On the other hand, a local-only hourly matching framework requires companies to match their electricity loads on an hourly basis using renewable energy sources on the same grid as the company's original consumption.

"Corporate energy buyers are making big decisions today that will shape clean energy markets for decades to come," said Lee Taylor, CEO of REsurety. "This tool provides much-needed visibility into the trade-offs between two leading approaches, so they can make informed decisions during the public comment period."

To use the free Scope 2 accounting calculator, visit calculator.gridemissionsdata.io.

If you are interested in learning more about the tool and how it can help your organization engage throughout the GHGP's open comment period, email contact@gridemissionsdata.io.

About REsurety
REsurety is the leading provider of data, software, and services to the clean energy economy, and operates the only transactional marketplace for clean power. Trusted by the industry's leading buyers, sellers, and investors, REsurety's proprietary data models, powerful technology platforms, and deep domain expertise empower confident, impactful decision-making and efficient, effective portfolio management. For more information, visit www.resurety.com or follow REsurety on LinkedIn.

About WattTime
WattTime is an environmental tech nonprofit that empowers all people, companies, policymakers, and countries to slash emissions and choose cleaner energy. Founded by UC Berkeley researchers, we develop data-driven tools and policies that increase environmental and social good. During the energy transition from a fossil-fueled past to a zero-carbon future, WattTime 'bends the curve' of emissions reductions to realize deeper, faster benefits for people and planet. Learn more at www.WattTime.org.

Media Contact
Nikki Arnone and Logan Varsano, Inflection Point Agency for REsurety and WattTime, 1 (719) 357-8344, nikki@inflectionpointagency.com, https://calculator.gridemissionsdata.io/

SOURCE REsurety and WattTime

Global impact accounting will also redirect corporate renewable investment from the US and Europe to the Global South.

The Greenhouse Gas Protocol is currently considering two proposals to revise the emissions accounting standard for electricity use and renewable energy purchasing. One proposal would add hourly matching & deliverability requirements, meaning that renewable energy could only be counted if matched to the hour and location where electricity is consumed. The other separate proposal describes how to report the consequential impact (the change to total global emissions) of projects, regardless of their time and location (this is also sometimes referred to as impact accounting or emissions matching).

While there have been many studies that investigate the impact of the hourly matching requirement [1,2,3], there has not been an investigation into the global scale impact of the deliverability requirement (procuring renewable energy on the same grid as your load). Most studies have focused on voluntary renewable energy purchasing in the USA or Europe, which have the highest levels of renewable energy purchasing and comparatively low emissions per MWh. However, there are many countries in the world with much dirtier grids but low levels of renewable energy purchasing. Increased procurement of renewables in these countries could provide a much higher impact on avoided emissions per dollar spent, while simultaneously reducing health problems from local pollution and investing in historically under-invested economies.

We studied the impacts on global voluntary renewable energy purchasing that could result from an hourly matching & deliverability standard and separately, from an impact accounting standard. We found that for a fixed cost, impact accounting avoids over 211 MT CO₂ per year, 4.7 times more than hourly matching with deliverability.

Methodology and Data

To model this, we simulated procurement portfolios globally under both an hourly matching & deliverable standard (“hourly matching” from here on) and an impact accounting standard. While the GHGP Scope 2 protocol is used globally, it is a voluntary standard that not all companies choose to follow. To estimate the relative levels of participation, we used the amount of purchased renewable energy from the 2024 Corporate Renewable Electricity Sourcing Trends report published by CDP. This report only covers companies that reported their location-based scope 2 emissions to CDP, which serves as a reasonable representation of the distribution of voluntary corporate purchases under the GHGP today. The distribution of historical voluntary purchasing is heavily skewed to the Global North, with the highest levels of renewable energy purchasing in Europe excluding Russia (175 TWh) and the USA (124 TWh). 

We modeled the purchasing decisions using a linear program (LP) method, which optimizes for the least-cost global voluntary energy purchasing of wind, solar, and battery resources subject to local hourly matching and emissions matching constraints. All procurement is assumed to be new build and fully additional. Global technology costs are taken from the IEA’s 2024 World Energy Outlook. We used the capital and operating costs for 2030 under the “Stated Policies” scenario. To annualize the capital costs, we amortized the costs over a 25-year lifetime and apply a 10% additional cost of capital. 

For hourly matching, we added the matching and local procurement constraint for an amount of load equal to the purchased renewable energy in each country (as reported by CDP). For impact accounting, we measure the induced emissions from load and the avoided emissions from renewable projects using the Combined Marginal Emissions Rate (CMER), which is the combined average of the Marginal Build Emissions Rate (MBER) and the Marginal Operating Emissions Rate (MOER). There is no location constraint for impact accounting, so projects can be selected from anywhere on the globe. To ensure that the solutions are reasonable, we add a constraint that the procured projects cannot exceed more than 20% of the total existing capacity from all generators in the country. This guarantees a solution where projects are spread among many countries, instead of concentrated in a single country with a volume that is impractical or unrealistic. If this constraint were removed, the model would concentrate procurement in a few countries with the highest emissions avoidance per cost, further amplifying the advantage of global impact accounting over hourly matching.

Global Impact Accounting Reduces More Emissions Per Dollar

In 2024, corporations procured a total of 562 TWh of clean energy globally. While we don't know the total cost of those clean energy purchases, if those 562 TWh of clean energy were instead procured in locations that maximized their avoided emissions, that portfolio of renewable energy procurement would cost $4.6B and avoid 211 MT of carbon emissions per year. Alternatively, that same $4.6B spent towards a 98% hourly match with local deliverability requirements, would only avoid 45 MT CO₂ per year (4.7 times fewer avoided emissions). We chose to compare both strategies at a fixed amount of spending, instead of a fixed level of participation, because hourly matching portfolios are significantly more expensive than impact accounting portfolios. The total cost for a 98% hourly matched portfolio is 16.5 times more expensive than impact accounting. 

While some companies may be willing to pay a premium for reducing their scope 2 accounting, the expected trend is that fewer companies will voluntarily offset their scope 2 emissions as the cost of doing so increases because of basic demand elasticity (we explored this in a previous post analyzing participation vs. costs). Instead of assuming that participation will stay the same regardless of costs, as previous studies have done, we instead assumed there is a fixed budget available for voluntary corporate procurement. For the cost of all participants achieving 100% emissions matching, only 6% of participants could achieve an hourly matching score of 98%. While the exact amount and willingness to pay are not known, the difference in avoided emissions per dollar remains.

This difference in impact can be understood by looking at the average amount of avoided emissions per dollar spent for each strategy: 100 lbs CO₂ per $USD for impact accounting vs. 21 lbs CO₂ per $USD for hourly matching. These differences in avoided emissions per dollar spent reflect the fact that grids with historically high voluntary RE development are not grids with the highest marginal emissions rates.  Below is a list of the top 10 countries for RE purchasing and the top 10 countries by avoided emissions rate per dollar. The countries with the highest levels of RE purchasing are largely in the US or Europe, but also include China and Brazil. China is the only country with high levels of voluntary RE purchasing to also appear in the list of high-impact countries, which are primarily countries with developing economies in the Global South that have very low levels of voluntary RE purchasing today and high levels of fossil fuel generation.

Below, we also plot the average avoided emissions per dollar for the 5 largest countries by load, along with the average aggregated by region, excluding those 5 countries. Comparing the average avoided emissions per dollar and the level of existing purchases of renewables shows where today’s investing is highly concentrated in locations with low avoided emissions per dollar and locations with more cost-effective impact are underinvested. India and China have an avoided emissions impact of 114 and 99 lbs CO₂/$USD respectively, compared with a rate of 34 and 27 lbs CO₂/$USD for Europe and USA respectively. The average rates for the Americas and Asia, at 96 and 83 lbs CO₂/$USD, are higher than the average rate in Africa of 54 lbs CO₂/$USD. The aggregated rates are averages, and the countries inside a region can still have a large spread of avoided emissions rates.

Impact Accounting Directs Investments from the Global North to the Global South

We analyzed the locations where annual RE spending could go under an hourly matching and an impact accounting standard with the same amount of total investment. Under hourly matching, the local matching requirement means investment would be concentrated in the US and Europe, similar to how it is today. Under impact accounting, the optimal distribution of investment today is almost entirely in Asia. This means a dollar invested in Asia will avoid the most CO2. However, investors may prefer other locations when non-climate factors are considered, and they can still choose more impactful locations outside of Asia that aren’t in their local grids. 

A consequential impact accounting standard without a local matching requirement could incentivize companies based in the Global North to purchase renewable energy projects in countries in the Global South for much more cost-effective decarbonization than local hourly matching. This could potentially provide an economic benefit to these countries by creating demand for RE projects, as well as pressuring grids to allow renewable energy purchasing agreements, such as VPPAs, which would make even more RE development possible. In addition to the economic and carbon benefits, many of these countries have very poor air quality from fossil fuel generation, leading to significant health problems and loss of life. A recent study found that air pollution in India increased deaths by 1.5 million per year. Increased development of renewable energy would displace fossil fuel generation in many of these countries, reducing global carbon emissions and improving local health at the same time.

Why Scope 2 Should Embrace a Global Approach to Procurement

Research suggests that local hourly matching in the US and Europe could help reduce meaningful amounts of emissions only at high levels of matching and only if it includes an additionality requirement, which the current Scope 2 proposal does not. However, achieving a high level of additional hourly matching has also been shown to be up to four-times more expensive and might reduce voluntary participation. The local deliverability requirement also has the impact of continuing to concentrate renewable energy investment in the US and Europe, where significant progress on decarbonization has already been made, so adding it would even further erode the emissions reduction effectiveness of the accounting standard. 

A change to the Scope 2 protocol in favor of local hourly matching would undermine the overall effectiveness of voluntary corporate renewable energy purchasing. Local hourly matching is much less efficient than global impact accounting, which avoids more emissions per dollar. Global impact accounting could increase the impact of voluntary renewable energy purchasing in two ways: first, each dollar spent achieves greater emissions reductions, and second, more actors are likely to participate due to the lower costs. In addition, hourly matching would continue to concentrate renewable energy development in regions such as the U.S. and Europe, which already have a strong appetite for grid decarbonization, while limiting investments in countries where benefits are greater.Instead, allowing for impact accounting regardless of location could direct investment to countries that are at the beginning stages of decarbonization. Prioritizing these countries could reduce more emissions while addressing global inequity at the same time. Corporations such as Salesforce, Heineken and Amazon have already begun to purchase renewable energy across Africa, Southeast Asia and Latin America in order to prioritize high impact projects. A change to the Scope 2 protocol in favor of local hourly matching threatens the future of projects like these, since many would not be credited under such a standard. A global consequential impact accounting standard would instead incentivize companies to explore outside of their local boundaries and pursue more impactful projects worldwide.

Download the white paper PDF:
Measuring the Carbon Impact of Battery Energy Storage Systems

Executive Summary

As the deployment of commercial-scale battery energy storage systems (BESS) accelerates, companies are seeking a common standard for quantifying the system-wide emissions impact that they cause.Companies that operate BESS are also integrating real-time emissions forecasts as signals to optimize the timing of charge/discharge cycles. To the extent that the goal of this strategy is to measure and reduce CO2 emissions into the atmosphere, both the measurement and control signals must use consequential emissions factors to measure and achieve the desired outcome.

This study assesses an Amazon-enabled BESS in California to demonstrate a practical way of estimating the atmospheric CO2 emissions caused by a BESS (including the system-wide short- and long-run impacts) using freely and globally available data. This study also showed that a battery can be operated to achieve multiple objectives (revenue and CO2 avoidance) by very simply combining both objectives into the control signal. It also shows the high cost that can come from using a CO2 signal that doesn’t measure consequential atmospheric emissions impact (e.g., hourly average emissions rates as used in GHG Protocol Corporate Standard Scope 2 reporting).

Estimating the Impact of BESS is Practical

WattTime analyzed an Amazon-enabled BESS in California as a case study to demonstrate a practical method for estimating the consequential emissions impact of a BESS. We used an approach consistent with well-established guidelines and standards for consequential analysis and emissions factors that are freely and globally available. This approach is accessible to any party operating a BESS today.

BESS Can Achieve Multiple Objectives

We found that when the BESS had been operated to maximize revenue, it also avoided substantial CO2 emissions. This outcome would not occur everywhere; it is more likely in places with surplus renewables whose curtailment aligns with negative wholesale prices.

We also analyzed several theoretical scenarios for dispatching the BESS for multiple objectives. We found that there was significant additional potential to avoid CO2—up to 45% more—by combining emissions and price signals when optimizing the dispatch timing of the BESS (this technique is applicable everywhere, with varying degrees of emissions upside).

Different companies may have different budgets and different ideal outcomes. We demonstrated that the objective outcomes can be balanced by customizing the weight of each. There’s a wide range of CO2 abatement costs, from $45 to $170 per tonne, that achieve better than 85% of the best-case outcomes for both objectives. For example, the BESS could avoid 30% more CO2 emissions, while only giving up 4% of maximum revenue, at an abatement cost of $68 per tonne.

The Risks of Optimizing to Reduce Hourly Scope 2 Footprint

Many companies produce annual carbon accounting inventory reports using the GHG Protocol Corporate Standard under Scope 2 for electricity, using data of annual granularity. For BESS to be reflected in this inventory, hourly accounting is necessary. However, this shift to hourly Scope 2 accounting using an attributional framework could incentivize BESS optimization using an attributional signal (i.e., average emissions rates). There are significant climate, health, and financial risks to companies using this attributional framework to guide operational strategy or decision-making. To quantify those risks, we analyzed the outcomes for a hypothetical case where the BESS was optimized to minimize a Scope 2 carbon footprint, measured hourly.

Optimizing the BESS to reduce a company’s Scope 2 hourly carbon footprint would cost $657 per tonne of CO2 inventory reduction. While it would reduce carbon footprint on paper, it would cause an increase in CO2 in Earth’s atmosphere by an estimated 3,509 tonnes. The real-world impact of such an approach extends beyond GHG emissions. On coal-powered grids this increase in CO2 emissions would be coupled with an increase in co-pollutants(e.g., particulate) emissions, which are damaging to human health and cause premature death. This shows the high cost that would come with operating a BESS to reduce a company’s attributional carbon footprint on paper instead of aiming to reduce atmospheric CO2.

Download the white paper PDF: Measuring the Carbon Impact of Battery Energy Storage Systems

Hourly matching only accelerates renewable energy progress if additionality is part of the standard

The current proposal for an hourly matching standard in the Greenhouse Gas Protocol Scope 2 reporting standard does not include requirements that matched energy be additional. This means that voluntary corporate clean energy buyers could claim energy attribute certificates (EACs such as RECs or GOs) from already-built clean generation resources towards reducing their carbon footprint. This will likely lead to lower amounts of clean energy on the grid and higher emissions compared to a stricter standard.

Additionality is defined as an intervention that causes an action that would not have occurred otherwise. For example, a corporation signing a voluntary PPA for solar or wind energy (the intervention) provides the financial certainty for a new clean energy project to get financed, built, and interconnected to the power grid (the caused action). This has long been understood as a critical principle of clean energy procurement necessary to cause the desired reduction in carbon emissions (Bjørn et al. 2025).

Previous studies have reported that hourly matching can reduce emissions, but almost all of them assume at least some level of additionality for the procured renewable resources. Only one work (Ricks et al. 2023) considered hourly matching without an additionality requirement, in the context of US hydrogen production, and found that without additionality “a 100% hourly matching requirement loses all of its consequential impact." 

In order to understand the impacts of an hourly matching standard as it is currently proposed, we used the PyPSA-Eur capacity expansion and dispatch model to analyze the impacts of an hourly matching standard with and without additionality requirements in the European grid in 2030. We find that a non-additional hourly matching standard has little to no impact on total system emissions.

How our analysis modeled additionality and hourly matching

Because true additionality depends on a counterfactual, it can be difficult to determine outside of models. Instead, a “new build” requirement is often used as a benchmark for additionality in renewable energy. Many groups have also proposed that for a project to be additional, there needs to be a long-term contract, which has been shown to significantly reduce risk for renewable project financing.

Meanwhile, purchasing energy from an existing project that has already been built and is already in operation is — by definition — not additional, since the action (building the generation resource) happened before the intervention (purchasing the RECs).

We modeled additionality using scenarios where only new build resources are allowed to count towards the hourly matching goals, and modeled non-additionality using scenarios where clean generation of any age can count towards the hourly matching goals (consistent with current GHGP Scope 2 proposals).

From an economic perspective, consumer demand for hourly matched RECs could increase the supply of clean energy, if the demand is high enough. In practice, we see that supply of unbundled RECs often surpasses demand, leading to low REC prices that have little impact on causing additional new renewable resources to be built.

Hourly matching proponents argue that its time-matching requirement will make REC supply scarce during certain hours, driving up the cost of RECs in those hours and leading to more investment in clean resources that generate during those times. However, this effect only occurs if the demand for RECs in those hours substantially exceeds the supply.

If unbundled RECs from existing generators are allowed (as in the current Scope 2 proposal), our modeling indicated that in the case of the European grid in 2030, a demand for clean energy attributes from 25% of all commercial and industrial (C&I) load is insufficient to cause investments that lead to significant emissions reductions.

Modeled scenarios

We also investigated the impacts of different methods of accounting for clean attributes of energy consumed from the grid.

• No Grid Contribution to Carbon Accounting: First, we consider the scenario (“No Grid”) where no attributes from the grid are counted, which replicates the formulation of hourly matching that was used in Xu et al. 2024. This scenario only counts purchased clean energy toward carbon accounting.
• Grid CFE - Imports: Next, we consider a scenario (“Grid CFE - Imports”) where clean attributes are counted proportional to the share of clean energy on the grid times the amount of energy “imported” from the grid (the gap between procured energy and total load). This is the formula initially proposed by Google and used in the study by Riepin and Brown. 
• Grid CFE - SSS: We then consider the scenario (“Grid CFE - SSS”) where consumers can count credits from their Standard Supply Service (SSS), which are clean energy credits procured by their utility and attributed to consumers proportional to their load. To our knowledge, this method of hourly matching has not been studied before, but is an element of the current standard proposed by the GHGP. We model this for corporate purchasers by allowing them to count a number of MWhs of clean energy equal to the share of carbon free energy on the grid times their total load in addition to any clean energy they procure directly. 

For all three of these scenarios, we modeled a requirement that procured resources are all new build (additional). We then modeled the scenario (“No New Build Req”) where there is no new build requirement by allowing consumers to count any amount of clean energy credits up to the total amount available on the grid.

No additionality means no impact

Without a new build requirement, we find that hourly matching has no emissions benefit for matching levels up to 90%. Even at a 100% hourly match, it has only a small benefit (4 MT) compared to the emissions caused by the load (62 MT). This is likely because there is a large amount of carbon-free energy already on the grid in Europe in 2030 without the addition of corporate procurement. If the corporate procurement is not limited to new build, buyers can take credit for the many carbon-free generation sources that already exist on the grid, including wind, solar, nuclear, and hydro. These purchases are non-additional, so they do not lead to changes in total system emissions. To achieve 100% matching, some additional resources are required, but they amount to a comparatively small amount of wind and battery storage resources. The battery storage resources are mostly dispatched to charge during times when there is excess CFE credits available and discharge during hours when there are fewer.

If a new build requirement was added, hourly matching is only impactful at high levels of hourly matching or if grid resources are not counted towards the hourly match. But these high-impact scenarios are also much higher in cost. Hourly matching that counts grid CFE either proportional to “imports” or SSS can have a significant impact on emissions if 100% hourly matching is achieved. However, below 100% matching, the emissions-reduction impact is small to non-existent. Again, this is likely caused by the high levels of CFE already on the European grid, which means corporate buyers can take credit for those existing resources and have a fairly high hourly matching score. The scenarios where no CFE from the grid is counted have a higher impact at all levels of matching, but also come at a much higher cost, exceeding €120 Billion in the 100% matching case. These high costs could be a deterrent, reducing the number of corporations willing to pursue voluntary renewable purchasing.

These results show that the specifics of how an hourly matching standard is written can lead to massive differences in reported emissions without any change in real-world grid decarbonization. The current proposed standard, which lacks a new build additionality requirement, will increase the difficulty of implementation by requiring more detailed accounting, but is likely to lead to little to no actual reduction in emissions. Adding a new build requirement to the standard could increase the impact, but it is highly dependent on how grid resources are counted towards the standard. The scenarios where impact is high come with a high cost however, which corporate buyers may not be willing to pay. This study also highlights the importance of considering all of the details when comparing a proposed standard to existing studies, as those studies may not apply to the proposed standard (as is the case here). This is the first time that hourly matching without a new build requirement (as proposed) has been studied, so previous research on hourly matching should not be used to project the impacts of the current proposed standard.

These results are part of a larger study we plan to release in the near future. If you are interested in learning more about it, or would like to access the code or data that was used to model these scenarios, please contact nat@watttime.org.

hero image: iStock / shaunl