How to calculate and reduce the carbon emissions of your website?

How can you estimate and reduce the carbon emissions from the use of your website, a new website resource may help to answer your problem.

With claims that the internet use consumes over 416TWh per year, which put into perspective, that’s more than the energy consumption for the whole of the United Kingdom & the electricity consumption can only rise with our increased business and personal Internet use, is there a way to estimate carbon emissions from website use.

A new website offers a solution to understanding and quantifying your carbon emissions from Internet use…

Like many other businesses, my consultancy, onePlanet Solutions, makes extensive use of the Internet from the presence of our business website: & our environmental resources at to the use of environmental resources at professional institutes, such as and

As part of the quantification of my business carbon emissions, I found this new and innovative resource, which is both simple to use and provides a clear estimation of the carbon emissions and context to your Internet use.

The tool is Website Carbon Calculator, which is designed to be simple and give an estimate of website efficiency in terms of CO2 per page view (in grams) based on a test of the homepage of a website. 

It uses five key metrics to estimate the carbon emissions:

  1. Data transfer over the wire, when a website is loaded, the energy used is roughly proportional to the amount of data transferred.
  2. Energy intensity of web data covering hosting at the data centre, telecoms networks and by the end user’s computer or mobile device. 
  3. Energy source used by the data centre assuming that all websites use standard grid electricity for the telecoms network and end user, since there is no way to determine otherwise.
  4. Carbon intensity of grid electricity is based on the international average as reported by the International Energy Agency.
  5. Website traffic with all of this information, it is possible to understand the carbon emissions associated with an average user visiting any given website.  By multiplying the carbon per page view by the typical number of annual page views, you can then estimate the total annual CO2 emissions.

The methodology is not full comprehensive as, although, the carbon emissions calculator estimates the emissions by using known data, some of which is one or two years old and not specifically targeted at UK energy data. So it comes up with a good estimate for comparision purposes rather than producing a definitive carbon emission value.

Nonetheless, I thought, I would use the website emissions calculator to use on some known sites to see what was reported.

I chose three categories of site: Environmental Agencies, Environmental Institutes and Environmental Consultancies

For Environmental Agencies, I ran the four Environment Agencies I the UK: Environment Agency for England, Scottish Environment Protection Agency, Natural Resources Wales & Northern Ireland Environment Agency with a comparision with other Environment Agencies, such as German Environment Agency, European Environment Agency & United States Environmental Protection Agency.

A comparision of the CO2 per web page in grams for each of the Environment Agency sites showed that all but one, the German Environment Agency had values less than 1 gram with Northern Ireland Environment Agency & European Environment Agency at the lower end with 0.32 and 0.52 respectively. If the value for the German Environment Agency is correct then, at 5.85 grams it is the most carbon intensive website to visit out of all the Environment Agency websites.

I next turned to, Environmental Institutes as these provide membership support and environmental resources and are likely to be keenly access for environmental information.

All of the Environmental Institutes had higher estimate carbon emissions than the Environment Agencies excluding the German Environment Agency with the Institute of Environmental Management being the only Institute lower than 1 gram at 0.99 grams CO2 per page view.

Again, there was an outlier of the Society for the Environment with a significantly higher estimated carbon emissions at 5.88 grams CO2 per page view.

Finally, I looked at the estimate carbon emissions for Environmental Consultancies taking my own two websites: onePlanet Solutions and EMSmastery as a comparison, which record lower estimated carbon emissions than any of the sites tested.

Environmental consultancies have estimated CO2 per page view similar to the Environmental Institutes but higher than the Environment Agencies. An outlier is Stantec with an estimated value of 7.27 grams CO2 per page view.

I have summarised the estimated carbon emissions for each of the three groups tested with their minimum and maximum values as well as a useful benchmark of 1.76 grams CO2 per page view as the average for websites.

It should be emphasised that the Website Carbon Calculator is estimating the carbon intensity of the main webpage of the website. The estimate is based on a number of assumptions, which are necessary for the complexity of the management of website data across the Internet. It is a good point of comparison and brings us closer to the day, when Internet usage can be determined more accurately.

As a bonus, the Website Carbon Calculator has a link to an article on 17 ways to make your website more energy efficient in three areas: Design and Content, Development & Web Hosting.

For Design and Content, it is about the planning stage of the website or its revamp to ensure that you have the most efficient access to the website and its resources and not wasting carbon on inefficient User Experience or resources, such as images and video, which can add to the energy needed to load the web-page.

For Development, it is more about efficient use of the coding for the website, the use of specific technologies and optimising the website to improve the delivery of its resources for the end user.

And, finally, Web Hosting, which can be fine tuned to ensure that server resources are cached, so they are readily and more immediately accessible, & are hosted in a energy efficient host close to your end-user.

I hope that this article has given you an insight into how you can start to estimate your website usage in terms of carbon emissions. With your estimated carbon emissions, there is an opportunity to improve the efficiency of your website to ensure that it is more energy efficiency and less carbon intensive in serving up resources for your end-users.

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