Why We Need a Green Perf Metric

Main Takeaways

• Much of web performance optimization overlaps with sustainable web development practices – especially when it comes to reducing the amount of data transferred on a site and implementing performance budgets to prevent regressions.
• The biggest impact web perf experts can make with regards to sustainability involves non-technical actions:
  • learning about sustainable software practices
  • raising awareness for the topic
  • helping to determine what not to build and what to delete
  • taking the entire lifespan of data products into consideration
• While currently measuring the carbon impact of websites relies on proxy metrics and rough estimations, we still should still observe them and investigate problems.
• We need better metrics and APIs to better estimate emissions due to device use and embodied carbon. Just imagine how easily we could measure if we had APIs in every browser like this:

Navigator = {
    deviceAge: 2,
    embodiedCarbon: 8,
    // ...
}
PerformanceSessionTiming = {
    totalTransferSize: 2220, // including request and response headers
    totalTransferredJS: 750,
    // ...
}
PerformanceMeasure = {
    detail: {
        cpuTime: 2342,
        gpuTime: 366,
        energyImpact: .66,
        watts: 0.00014
    }
}

Resources

• Greenhouse Gas Emissions by Sector, ourworldindata.org
• “The real climate and transformative impact of ICT: A critique of estimates, trends, and regulations” (2021) by Charlotte Freitag, Mike Berners-Lee, et al.
• “The Scientists Watching Their Life’s Work Disappear”, New York Times, Oct. 26, 2023
• The Jevons Paradox, Wikipedia
• The EU’s Corporate Sustainability Reporting Directive (CSRD)
• California’s SB 253, the Climate Corporate Data Accountability Act (CCDAA)
• Web Sustainability Guidelines, a W3C Community Draft Report
• An overview of the Web Sustainability Guidelines with the highest impact and lowest-medium effort
• Building Green Software (2024, preview) by Anne Currie, Sarah Hsu, Sara Bergman
• “Why do estimates for internet energy consumption vary so drastically?” by Tom Greenwood
• Green Software Practitioner by the Green Software Foundation
• “Calculating Digital Emissions” on sustainablewebdesign.org
• Page weight report on HTTP Archive