0. What Changed and Why

For over a decade, the web carbon industry has measured the wrong thing.

Every tool out there -- Website Carbon Calculator, Ecograder, Beacon, CO2.js -- rests on one idea: device energy scales with bytes sent. Multiply bytes by a constant. Call it a carbon score. Publish it as fact.

It is not fact. It never was. It was the best proxy when these tools were built. Credit to them -- it moved the talk forward when nothing else existed. But over time, a proxy became a standard. Agencies cite it in green reports. Standards bodies use it in guides. The industry treats it as real data when it is, at best, a rough guess -- and often a wildly wrong one.

Using bytes to guess device energy is like using a banana to measure a football pitch. You get a number. It does not tell you much.

Here is why: a 2MB page of compressed images and a 2MB page of heavy JavaScript look the same to a bytes model. They are not the same. The JS page forces the CPU to parse and run code for seconds. The image page decodes in moments on the GPU. These are very different energy profiles. No amount of tuning a bytes constant will tell them apart.

EcoPigs v2.0 replaces the proxy with real data.

On every scan, we open a Chrome DevTools Protocol (CDP) session. We capture real CPU time, layout work, and render steps from the V8 and Blink engines. We turn those into energy using device power profiles from hardware specs, research papers, and tested benchmarks. The result is a carbon score based on what the page actually did, not what a formula guessed from file size.

We tested this on our own site first. ebbb.io is a light, fast static site -- the kind the bytes-proxy should handle well. On desktop, the proxy guessed 12x too high. Across all device types, 71x too high. On mobile: 320x too high.

That is not a tuning problem. It is a method problem. It has sat at the heart of web carbon scoring for a decade. v2.0 fixes it.

1. Why We Built Something New

The web carbon industry has a data problem. Every tool -- Website Carbon Calculator, Ecograder, Beacon, CO2.js -- rests on one idea: device energy scales with bytes sent.

SWD v4 gives user devices 0.080 kWh/GB of energy (Malmodin et al. 2023). This is a proxy, not a reading. A 2MB image page and a 2MB JavaScript page score the same, even though the JS page makes the CPU work far harder. In our tests, a light page used 12x less device energy than the proxy said it would.

EcoPigs v2.0 replaces that proxy with real browser data. On each scan, we capture CPU time, layout work, and render steps from the engine itself. We convert those into energy using device power profiles from hardware specs and research papers. The result is a carbon score based on what the browser did, not what we guessed from the file size.

Every other tool runs a version of the same formula with the same data. They will always agree on the same site. But agreement is not accuracy. EcoPigs gives a different number because it measures something different: what the browser did, not what a formula said it should do.

2. The Five-Score System

EcoPigs shows five carbon scores. Each adds one layer of detail. This clarity helps you see what drives your number and how different inputs change it.

Grid Intensity Values Used

3. Measured Device Energy: How It Works

On every scan, our tool opens a CDP session and turns on performance tracking. After the page loads, we pull metrics straight from the V8 JavaScript engine and the Blink renderer:

What CDP Measures (main thread only)

These are real seconds of main-thread CPU work. They show what the chip actually did, not what we guessed from file size. Web Workers, Service Workers, and off-thread compositing are not included (see Limits).

Conversion to Energy

Three energy parts are worked out:

Comparison with Bytes-Proxy

For ebbb.io (a light static site, 838 KB transfer, 0.22s script time, scanned as desktop via Puppeteer):

Real data also shows the real difference. Two pages with the same byte size but different CPU loads get the same proxy score. Measured data shows the true gap:

• A 2 MB page with 0.1s script execution: ~5 mWh on desktop (screen-dominated)
• A 2 MB page with 3.0s script execution: ~25 mWh on desktop (CPU-dominated)
• The proxy gives both ~156 mWh

4. Per-Segment Grid Splitting

v1.0 used one grid value for all three segments. That is handy but not correct. Your server in London, the cables across the Atlantic, and the visitor's laptop in Berlin draw from three different grids with different carbon levels.

5. Core Scientific Principles

The core equation stays the same:

We track carbon across three segments and two emission types:

Operational Energy Intensity (kWh per GB transferred)

Embodied Emissions

We include the carbon locked in the making of the hardware that runs the web. This is turned into an energy-like rate (0.106 kWh/GB) using the global grid average.

How Server-Side Energy Is Estimated

EcoPigs does not read server CPU or memory use directly. Server energy is estimated as bytes sent x 0.057 kWh/GB. This is the same method used by SWD v4 and all other tools. Future versions may add server-side tracking where possible.

6. Updated Data Sources (February 2026)

What Changed from v1.0

7. Live Grid Tracking

A key difference is that EcoPigs uses live, local grid data. A fixed global average (494 gCO2/kWh in the SWD model) can be far off. A site hosted in the UK has a very different impact than one in a coal-heavy region.

EcoPigs shows grid carbon and energy mix but does not say which source is "better." A low-carbon grid may run on nuclear, hydro, wind, or a blend. The choice between low-carbon and renewable power is a value call we leave to you. We give the data. You decide what it means for your hosting.

Our Data Integration

Country Reference Values (Ember 2024 data, via Global Electricity Review 2025)

8. Conservative Baseline Assumptions

Our baseline uses cautious, upper-bound values:

This aligns with the GHG Protocol Corporate Standard (complete, clear, consistent, accurate, cautious) and follows ISO 14064-1 methods. EcoPigs reports have not been checked or verified against either standard by a third party.

9. Green Hosting: A Nuanced Approach

When a host is verified as "Green," we apply a 0.2 factor (an 80% cut) only to the Data Centre segment.

Green hosting does not reduce:

• Energy used by global network infrastructure
• Energy consumed by the end-user's device
• Embodied emissions from hardware manufacturing

This detail lowers the risk of over-counting the green hosting benefit. A green-hosted site still has network, device, and hardware-making emissions.

10. How We Compare

11. Scope and Boundaries

12. Versioning and Comparability

v2.0 uses the Ember 2024 global average (473 gCO2/kWh) for Baseline. v1.0 used 494. The grade bands (A+ to F) are the same, so grades still compare across versions. But raw gCO2 values from v2.0 will be a bit lower than v1.0 for the same page due to the updated grid value.

Grade Thresholds

Grades come from total emissions per view (gCO2), set against HTTP Archive page weight data:

Every report shows which method version was used. When you compare reports over time:

• Grade comparisons are valid across v1.0 and v2.0 (same thresholds)
• Absolute gCO2 values should be compared within the same methodology version, or with awareness of the 4.3% reduction
• The Traditional score uses the SWD v4 built-in grid (494) and provides the closest comparison to v1.0 values

The measured score (v2.0) adds to the other four. It does not replace them. You can track your traditional score (for industry benchmarks) and your measured score (for accuracy) at the same time.

13. Device Power Profiles

v2.0 adds four device power profiles. These turn measured CPU time, estimated GPU compositing, and screen-on time into energy numbers.

Source types: Values come from Academic (peer-reviewed papers), Manufacturer (published specs), and Community (repeatable tests by hardware testers -- not peer-reviewed but consistent and reproducible).

Academic References

1. Carroll, A. & Heiser, G. (2010). An Analysis of Power Consumption in a Smartphone. USENIX ATC.
2. Mahesri, A. & Vardhan, V. (2004). Power Consumption Breakdown on a Modern Laptop. PACS.
3. Microsoft IE Team (2011). Browser Power Consumption: Leading the Industry.
4. Torchbox (2024). How Much Power Do Web Assets Use? M1 MacBook powermetrics measurements.
5. arXiv:2205.11399 (2022). Energy Efficiency of Web Browsers in the Android Ecosystem.
6. arXiv:2401.15985 (2024). Dissecting software-based measurement of CPU energy consumption.
7. Stanford/Boneh (2012). Who Killed My Battery? WWW 2012.
8. ASE 2020. Energy Wars -- Chrome vs Firefox. RAPL-based browser energy comparison.

14. Relatable Metrics

Grams of carbon are hard to picture. We turn emissions into everyday examples so teams can share their impact clearly. All conversions use DEFRA 2025 UK grid data (0.177 kgCO2/kWh) where it applies.

These metrics are provided at both per-visit and annual (x10,000 page views) granularity. All relatable metrics use the same source constants defined in constants/carbonMethodology.mjs, ensuring consistency across all outputs.

15. Limitations

Being open about limits makes the method stronger, not weaker.

Measurement Scope

Energy Estimation

Methodology

16. References

Primary Research

• International Energy Agency (2024). Energy and AI. Updated data centre energy consumption to 415 TWh.
• International Energy Agency (2022). Data Centres and Data Transmission Networks.
• Malmodin, J. & Lunden, D. (2023). The energy and carbon footprint of the global ICT and E&M sectors 2010-2022. Telecommunications Policy.
• ITU (2024). Facts and Figures 2024. Global data transfer volumes.
• Ember (2025). Global Electricity Review. Country-level grid carbon intensity data for 2024. Source of 473 gCO2/kWh global average.

Standards and Frameworks

• GHG Protocol. Corporate Accounting and Reporting Standard.
• ISO 14064-1:2018. Greenhouse gases -- Specification with guidance.
• SBTi. Science Based Targets initiative -- ICT Sector Guidance.

Government Data

• DEFRA (2025). UK Government GHG Conversion Factors. Electricity factor: 0.177 kgCO2/kWh.
• National Grid ESO. Carbon Intensity API. carbonintensity.org.uk.
• U.S. EPA. Emissions & Generation Resource Integrated Database (eGRID).
• ENTSO-E. Transparency Platform. transparency.entsoe.eu.

Hardware Specifications

• Intel. ARK Product Specifications -- i5-12400. Package power and RAPL measurements.
• Qualcomm. Snapdragon 8 Gen 2 Product Brief. Big core cluster power consumption.
• EnergyStar. Display Product Database. Typical panel power consumption.

Industry Models (for comparison)

• The Green Web Foundation. CO2.js -- Sustainable Web Design Model v4. Uses 0.080 kWh/GB operational + 0.081 kWh/GB embodied for user device segment. 494 gCO2/kWh default global grid.
• Fershad Irani (2024). Exploring the Sustainable Web Design Model v4.