The internet has a carbon footprint — and your website contributes to it every time someone visits a page. The Neutraly’s Website CO₂ Emissions using a transparent, science-based model that includes data transfer, hosting efficiency, device energy, and traffic volume. Below, we explain in detail how we estimate the CO₂ impact of each pageview and the total emissions of your site.
Formula Overview
We use the following formula to estimate the average carbon emissions per page view (gCO₂e) of your website:
Average Emissions per Page View (gCO₂e) =
([(OPDC × (1 - Green Hosting Factor) + EMDC) + (OPN + EMN) + (OPUD + EMUD)] × New Visitor Ratio)
+
([(OPDC × (1 - Green Hosting Factor) + EMDC) + (OPN + EMN) + (OPUD + EMUD)] × Return Visitor Ratio × (1 - Data Cache Ratio))
This formula accounts for both the first-time visit (with full data load) and return visits (with partial data load due to caching), and separates emissions from different parts of the internet infrastructure.
Parameter Definitions:
| Parameter | Description | How to Get | Estimates from Research |
|---|---|---|---|
| OPDC (Operational – Data Center) | Emissions from energy used by data centers per page view | Estimate using Sustainable Web Design average | 0.5 – 0.8 gCO₂e |
| EMDC (Embodied – Data Center) | Emissions from manufacturing & lifetime infrastructure of data centers, averaged per page view | Use default from Estimating Digital Emissions or LCA studies | 0.15 – 0.3 gCO₂e |
| OPN (Operational – Network) | Emissions from internet routing (ISPs, backbone) per page view | Use global averages based on traffic energy intensity | 0.05 – 0.1 gCO₂e |
| EMN (Embodied – Network) | Emissions from producing networking hardware, averaged per page view | Use default average from published studies (optional) | ~0.05 gCO₂e |
| OPUD (Operational – User Device) | Emissions from the energy consumed by user devices while loading the site | Estimate based on page load size and average device power use | 0.2 – 0.5 gCO₂e |
| EMUD (Embodied – User Device) | Emissions from manufacturing user devices, averaged per page view | Use default from LCA (e.g., smartphones, laptops) | 0.05 – 0.15 gCO₂e |
| Green Hosting Factor | Share of energy from renewable sources used by your hosting provider (0 to 1) | Ask your hosting provider or check listings on The Green Web Foundation | 0.1 – 1.0 (1.0 = 100% green) |
| New Visitor Ratio | % of total page views from new users (not previously cached) | Use Google Analytics → Audience → Behavior → New vs. Returning | 0.2 – 0.6 depending on site type |
| Return Visitor Ratio | % of total page views from returning users | = 1 – New Visitor Ratio | 0.4 – 0.8 |
| Data Cache Ratio | Estimated % of page content cached locally by return visitors (e.g., via browser, CDN) | Use site audit tools (e.g. Lighthouse) or set default for typical websites | 0.3 – 0.8 |
Simplified Explanation the Website CO₂ Emissions
To simplify, think of each page view’s emissions as coming from:
- Data Centers (where your website is hosted)
- The Network (the internet infrastructure that delivers your content)
- User Devices (what people use to browse your site)
Each part contributes both:
- Operational emissions: CO₂ from electricity used during loading
- Embodied emissions: CO₂ from building the hardware used
Then, we calculate separately:
- New visitors who load your full site,
- Returning visitors who benefit from caching (less data = lower emissions)
Embodied vs. Operational Emissions
| Type | Description | Example |
|---|---|---|
| Operational Emissions | CO₂ released during day-to-day use of servers, networks, and devices | Electricity used when someone loads your site |
| Embodied Emissions | CO₂ released during the manufacturing, shipping, and installation of physical infrastructure | Producing servers, network cables, smartphones |
Neutraly includes both types in our estimates for a more complete picture of your site’s footprint.
How to get Values
Page Size and Data Transfer
We begin by scanning your website and calculating the average page size in megabytes (MB):
Page Size (MB) = Total Bytes Transferred ÷ 1,048,576
This includes HTML, CSS, JS, images, fonts, and third-party scripts. We scan the homepage and optionally multiple internal pages for a realistic average.
Data Energy Use per Pageview
We then estimate the energy consumed to deliver this data across the internet (network + data center):
E<sub>data</sub> (kWh) = Page Size (GB) × Energy Intensity (kWh/GB)
Typical average energy intensity is between 1.8 and 5.1 kWh/GB, depending on network type and global infrastructure. A common default we use for estimation is 1.8 kWh/GB (based on The Shift Project and DIMPACT).
Convert page size from MB to GB:
Page Size (GB) = Page Size (MB) ÷ 1024
Then calculate:
E<sub>data</sub> (g CO₂) = E<sub>data</sub> (kWh) × Grid Emission Factor (g CO₂/kWh)
Default global grid factor: 475 g CO₂/kWh
Device Energy Use
We estimate the energy used by the visitor’s device to load and render the page:
E<sub>device</sub> (kWh) = Device Power Draw (W) × Load Time (s) ÷ 3600
Typical device power (avg):
- Smartphone: ~2.5 W
- Laptop: ~15 W
- Desktop: ~60 W
Example (desktop, 5s load time):
E<sub>device</sub> = 60 × 5 ÷ 3600 = 0.0833 kWh
Then:
E<sub>device</sub> (g CO₂) = E<sub>device</sub> (kWh) × Grid Emission Factor</b>
For per-pageview average, we apply a weighted blend based on typical visitor device share.
Hosting Energy Adjustment
The carbon footprint of a website is heavily influenced by where and how it’s hosted. Some hosting providers run entirely on renewable energy or offset their emissions — while others rely on conventional, fossil-fuel-based electricity.
How We Determine Your Host Type
To determine your hosting provider’s energy profile, Neutraly checks your domain against The Green Web Foundation (TGWF) database. This is a publicly maintained list of verified green hosting providers around the world.
TGWF classifies a domain as:
- Green — if it’s hosted by a provider that:
- Uses 100% renewable energy, or
- Offsets emissions with certified renewable energy credits (RECs)
- Unknown — if there’s no verified data on the host
- Grey — if the provider is known not to operate with renewable energy or offers no transparency
We run automated checks using TGWF’s API to classify your domain accordingly.
Impact on CO₂ Calculation
Once hosting type is known, we apply an energy credit in our model:
| Host Type | Description | Hosting Adjustment Applied |
|---|---|---|
| Green Hosting | Uses 100% renewable energy or verifiable RECs | Up to 100% deduction of data center emissions |
| Partially Green | Uses mixed grid energy with partial RE offsets | Partial deduction (e.g., 50%) |
| Grey/Unknown | No data or known fossil-based infrastructure | No adjustment — full emissions applied |
Formula Impact
E<sub>hosting_credit</sub> = E<sub>data_center</sub> × Green Coverage %
If your host is green-certified, the emissions from data center operations are reduced proportionally — or even completely neutralized in the case of 100% renewables.
Why This Matters
Many carbon calculators ignore where your website is hosted, leading to over- or under-estimation of emissions. At Neutraly, we believe that rewarding climate-conscious infrastructure is key to driving web sustainability forward. This adjustment ensures that your efforts to choose a green host are recognized and reflected in your certification.
Technical Factors Affecting CO₂ Emissions
Technologies like caching, CDNs, code efficiency, and media delivery strategies all influence a site’s actual environmental impact.
| Factor | Positive Impact When… |
|---|---|
| Caching | Assets are stored locally or pre-rendered |
| CDN | Assets served closer to users geographically |
| Efficient Code | Minimizes JS, CSS, and unnecessary logic |
| Optimized Media | Images/videos compressed and responsive |
| Fonts | Use system fonts or subset custom fonts |
| Third-Party Scripts | Only essential tools are loaded |
| Backend Efficiency | Lightweight server logic, serverless infra |
| User Behavior | Faster, more focused browsing experiences |
References & Resources
Our methodology is informed by a wide range of peer-reviewed research and measurement tools, including:
- Google Lighthouse – for real-world performance and resource analysis
- WebPageTest – for detailed asset breakdown
- The Shift Project – for energy intensity per GB
- DIMPACT – for digital emissions modeling
- International Energy Agency (IEA) – for grid emissions and device power use
- IPCC Guidelines – for standardized emission conversion factors
We constantly refine our methodology as newer, better data becomes available.
The result: a comprehensive estimation of CO₂ per pageview, monthly and yearly emissions, and full transparency on what contributes to your digital carbon footprint.
From there, we direct your fee to verified carbon projects and issue your WSCP® Certified badge and certification page — showing your website supports climate action.