Greenly's methodology uses "cost & usage" billing files to derive physical data. It is an activity-based study that tracks electricity consumption, hardware depreciation and refrigerant leaks, and even differentiates emissions related to computation, data storage and data transfer. It is therefore a strict and comprehensive methodology that provides the best possible measurement of these emissions — including a representation of cloud emissions per service and per country, as well as the countries in which cloud operations run and the associated carbon intensity of electricity.
The types of GHG emissions of cloud providers include:

In our cloud analysis, these emissions are split between four different families of services.

This covers the usage of computation servers and processors (i.e. computing power) to run applications, websites or processes. The compute power consumed is measured in hours of vCPUs, which represent the usage of a share of one processor during one hour. Each type of CPU has a number of "cores" — a 4-core CPU can theoretically run 4 computations at the same time. Each core can be split into two "threads", one thread forming one vCPU.
Each vCPU hour used doesn't consume the same energy, depending on the processor behind it. To estimate the energy consumption, we use the TDP (thermal design power) and an estimated workload of 40% on average. Note that the power consumption of a processor is high even when it is idle, so running one processor at 100% of its capacity is better than running two processors at 50%.
We also calculate the impact of the amortization of servers, using data from the R740 LCA and the number of vCPUs used by the purchased service compared with the total number of vCPUs available. Finally, we calculate the impact of refrigerant gas leaks using a proxy based on electricity consumption and an ADEME × ARCEP study on European data centers.

Storage is measured in GB.month, so 1 GB stored during one year is equivalent to 12 GB.month. To compute the impact of storage linked to electricity and amortization, we rely on academic studies alongside the Dell R740 LCA for the impact of storage disks, comparing the electricity consumption of a server with or without storage disks to estimate the consumption per GB stored. A ratio of 25% of unused storage space is assumed, to account for meeting increases in demand.
Cloud providers offer different types of storage with varying availability. To account for the lower impact of "cold" storage compared with regular storage, Greenly uses a proxy based on the cost of a GB stored for each SKU: we first calculate the cost A of a regular storage solution, then compare it with the cost B of each cold-storage SKU. Our conversion factors are multiplied by the ratio (B/A), the hypothesis being that the cost of a service is almost a linear function of electricity consumption. Finally, we calculate the impact of cooling (refrigerant gas leaks) using a proxy based on electricity consumption and the ADEME × ARCEP study on European data centers.

Data transfer is measured in GB and represents the amount of data transferred either between the client's data center and their users, or internally between different locations and servers (to duplicate data, for example). We distinguish three types of data transfer:

For all the services we cannot map onto the first three categories (monitoring, support, security, logs, IP addresses, etc.), we use this category, which is assessed with an expense-based approach, applying the monetary ratio calculated in the first three categories.