Do not rank AWS, Microsoft Azure, and Google Cloud by headline targets or a single customer-footprint total. First check whether the figures cover the same services and emissions, use the same electricity-accounting view, allocate shared infrastructure in comparable ways, and describe the same workload, region, and period. The providers’ published methodologies do not establish a harmonized, like-for-like comparison.
What the headline figures do—and do not—tell you
A cloud carbon figure is an estimate produced within a defined accounting boundary. It is not automatically a complete measure of a provider’s climate impact, nor a direct measure of the emissions your organization would cause by moving an application there. A customer-facing footprint also depends on how a provider assigns shared data-center and hardware impacts to particular products, accounts, and workloads.
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The comparison below reflects public provider methodology and product documentation reviewed on October 7, 2026. It describes what those documents say, not an independent measurement of provider workloads or a third-party ranking. Methodologies and reporting features can change.
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| Comparison point | AWS | Microsoft Azure | Google Cloud |
|---|---|---|---|
| Service boundary and exclusions | AWS’s documented estimate covers selected owned or controlled facilities and infrastructure sources. It includes such sources as backup-generator fuel, refrigerants, and natural gas at included facilities. Warehouses, manufacturing facilities, offices, and some customer-facility deployments are excluded. Source: AWS’s cloud emissions boundary documentation. | Microsoft says its methodology covers Azure and Microsoft 365 core cloud services and describes hardware lifecycle categories. The methodology page reviewed does not establish a complete list of facility exclusions. Source: Microsoft Azure emissions methodology. | Google describes allocating computing-infrastructure impacts to cloud products and customers based on usage. The methodology reviewed does not establish an equivalent list of facility exclusions. Source: Google Cloud Carbon Footprint methodology. |
| Scope coverage and lifecycle detail | AWS defines Scope 1 as direct emissions from owned or controlled sources, Scope 2 as purchased-energy emissions, and Scope 3 as other value-chain emissions. Selected Scope 3 items include upstream fuel and electricity activity, embodied carbon for IT hardware, data-center buildings, and non-IT equipment. Source: AWS’s cloud emissions boundary documentation. | Microsoft reports Scope 1, Scope 2, and selected Scope 3 emissions. Its listed Scope 3 categories are 1, 2, 4, 5, 9, and 12; the methodology describes hardware lifecycle stages including raw-material extraction, component aggregation, and end-of-life management. Source: Microsoft Azure emissions methodology. | The methodology describes customer allocation of infrastructure impacts, but the Google documentation reviewed here does not establish a directly comparable list of Scope 1 and Scope 3 categories for the customer footprint. Source: Google Cloud Carbon Footprint methodology. |
| Electricity accounting | AWS describes both location-based and market-based Scope 2 values. Source: AWS’s cloud emissions boundary documentation. | Microsoft says its Scope 2 calculation considers data-center and server efficiency, grid emission factors, renewable-energy purchases, and infrastructure power usage. The methodology page reviewed does not establish whether customer-facing reports expose both accounting views separately. Source: Microsoft Azure emissions methodology. | Google reports location-based and market-based Scope 2 data. Its methodology says location-based values do not account for Google’s carbon-free electricity purchases, while market-based values do. Source: Google Cloud Carbon Footprint methodology. |
| Allocation and customer-level detail | AWS provides customer emissions methodology and reporting resources. The resources reviewed do not establish a comparable service, project, region, and month breakdown. Source: AWS customer emissions resources. | Microsoft describes allocating data-center emissions using customer usage, including usage time for storage, compute, and network. The methodology page reviewed does not establish the same customer-facing breakdown dimensions as Google’s product page. Source: Microsoft Azure emissions methodology. | Google describes a bottom-up approach using machine-level power and activity monitoring, with allocation by product and customer usage. Its product page says customers can inspect data by service, project, region, and month and export it to BigQuery. Source: Google Cloud Carbon Footprint methodology and product page. |
| Assurance and changes | AWS’s resources page links an independent assurance letter for its methodology. That is not, by itself, evidence that every customer-specific result is assured. Source: AWS customer emissions resources. | The Microsoft methodology page reviewed describes standards and calculations but does not establish an assurance status. Source: Microsoft Azure emissions methodology. | Google says customer-specific data has not been third-party verified or assured and may change as methodology or data sources change. The product page separately describes a third-party review statement about the methodology; that is not assurance of each customer result. Source: Google Cloud Carbon Footprint methodology and product page. |
Which details matter most in a fair comparison?
Start with the boundary, not the label
“Scope 3 included” is too broad to establish comparability. Check which value-chain activities are counted, whether hardware and buildings are included, and what facilities or deployments fall outside the estimate. The AWS and Microsoft documents, for example, describe different included activities and lifecycle categories. A figure with a narrower boundary may look lower without representing a more efficient workload or a lower total impact.
#1 Best Overall
Keep location-based and market-based electricity results separate
Location-based accounting reflects the emissions intensity of the electricity grid where power is used. Market-based accounting incorporates eligible contractual electricity attributes or carbon-free energy purchases. The two views answer different accounting questions; do not substitute one for the other or compare one provider’s market-based result with another provider’s location-based result. Google’s sustainability guidance recommends looking at both when evaluating workload impacts.
Inspect how shared infrastructure is assigned to you
Cloud resources share data centers, networking, and hardware. A customer footprint therefore depends on an allocation method, not just a meter attached to one application. Find out what usage measures drive the allocation, whether the figures can be isolated at the service or project level you need, and whether estimates are recalculated when methods or data sources change. If a provider supplies only an aggregate figure, it may not support a workload-level comparison.
Distinguish a reviewed method from assured customer data
Assurance claims need a precise object: an organization’s reported data, a customer-specific footprint, a calculation method, or some combination. A third-party review of methodology does not establish that every customer result has been independently verified. Record the exact statement the provider makes, and mark assurance as “not stated” rather than assuming it exists when the documentation is silent.
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A practical workflow for comparing providers
- Define the workload. Specify the application or service, required cloud capabilities, performance and availability targets, and data-residency constraints. Without these, a provider comparison may be comparing different work rather than different ways to run the same work.
- Fix the comparison window and region. Use the same reporting period and, where feasible, comparable regions. Record the provider’s service boundary for each estimate, including material exclusions.
- Capture each electricity view separately. Record location-based and market-based values where available. Note which is missing rather than treating the remaining value as a substitute.
- Write down scope and lifecycle coverage. Record the reported scopes, the specific Scope 3 categories, and whether hardware, buildings, fuel, and other relevant lifecycle activities are counted.
- Document allocation and data resolution. Note the usage measures behind the allocation, the smallest useful reporting level available, and whether historical results can change after a methodology or data-source update.
- Record assurance precisely. Identify whether customer-specific data is assured, only a methodology is reviewed, or the documentation does not state an assurance status.
- Compare the outcome, not only the footprint. Evaluate emissions alongside the same workload’s cost, performance, availability, and service constraints. Test whether reducing idle or oversized resources changes the provider-reported result.
Use the comparison for the decision you actually need to make
For procurement
Ask providers to explain boundary differences and reporting dimensions before setting a carbon-based selection criterion. If the comparison relies on different Scope 3 coverage or electricity views, disclose that limitation instead of presenting a single ranked score as if it were like-for-like.
For corporate inventories
Follow the accounting approach your organization uses, preserve the provider’s stated boundary and method, and retain enough detail to explain how the reported figure was obtained. Do not silently combine market-based and location-based figures or treat methodology review as assurance of the customer value.
For engineering
Use the narrowest available service or project data that matches the workload, then investigate its resource use and region. Google Cloud’s Well-Architected sustainability guidance states, “Every resource that you create in the cloud has an associated carbon footprint.” The guidance was last reviewed January 28, 2026 UTC. This is a useful reminder to include resource choices in engineering decisions, not a provider ranking or a claim that all resources have equal impact.
Rank #4
Provider guidance identifies service choice, resource consumption, grid carbon intensity, and energy procurement as relevant influences on reported workload emissions. Consequently, moving an unchanged workload to a different provider is only one possible intervention; resizing or removing unnecessary resources may also change its footprint.
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