The carbon intensity of electricity in Tailpipe’s methodology accounts for how carbon emission-heavy the local grid mix of the data center region hosting the customer’s instance is. Grid mix is the proportion of different power generation sources that supply a country’s energy grid. Some countries, such as Norway, Paraguay, and Nepal, generate more than 90% of their electricity through renewable sources, and therefore data centers based in these countries will produce very low levels of carbon emissions (Statista, 2024). Others, such as Algeria, Turkmenistan, and Botswana, rely on fossil fuels for more than 90% of their electricity, leading to very high carbon emissions for local data centers (Statista, 2024).
Some data centers do also generate their own energy on-site. AWS does not disclose how many of their data centers utilize on-site power, so Tailpipe assumes that all data centers use only grid mix electricity. Cloud Service Providers also frequently claim that they will soon power all of their data centers with renewable energy. Whilst this is an admirable goal, both AWS and Azure rely upon energy matching: AWS claims to have achieved ‘100% of the electricity consumed by Amazon matched with renewable energy sources’ and Azure pledging ‘100 percent of our electricity consumption, 100 percent of the time, matched by zero carbon energy purchases by 2030’. This means that their data centers can still be powered through local grid mixes that utilize fossil fuels, if the CSPs are investing in renewable energy projects elsewhere. Because Tailpipe measures the actual emissions generated by instance usage, it does not consider CSPs’ energy matching projects to compensate for customer’s, or the provider’s, responsibility for carbon emissions.
AWS operates data centers in 29 regions around the world; Azure operates in 41. Tailpipe matches these regions with national grid mix data provided by Ember, an internationally recognized platform that publishes monthly grid mix statistics taken from countries and their energy suppliers. Ember determines a country’s carbon intensity by multiplying the quantity of each energy source within a country by each source’s carbon intensity figure. Carbon intensity is measured in grams of CO2e emitted per kilowatt-hour of electricity generated. Because Ember only provides monthly grid mix data, Tailpipe uses more granular national data where possible. For example, for data centers based in the UK, Tailpipe uses half-hourly National Grid mix data from Carbon Intensity.
Power Transmission Losses
The final stage of the calculation factors in power supply losses from the energy generation source. Power stations are not able to transfer 100% of their energy to their customers; approximately 8% of electricity is wasted between power source and destination in the UK (Statista, 2024). This loss results from inefficiencies within power stations and across the transmission lines and transformers. The percentage of power lost can vary from country to country, but Tailpipe uses 8% as an estimated figure based on the UK’s grid. Tailpipe therefore multiplies the organization’s power consumption figure by a factor of 1.08 to account for these losses.
