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The method behind Energyfriendlyweb: How we calculate your website

Our calculator is a tool to show how large your website is and whether your website is optimised. It examines a single page on your website, i.e. the URL you enter, e.g. your landing page. The result shows the potential to make the page less resource-intensive, i.e. to reduce the amount of data on the page so that sending data from server to browser and displaying the page requires less power. Our analysis also looks at whether your solution is hosted using green energy.

Optimising your website makes it faster. It upgrades the user experience, and it also benefits your SEO.

Why do we focus on the size of the website and not on the carbon footprint?

At present, there are too many unknowns involved in accurately measuring the climate impact of one website. For example, we don't know how far the page has to travel to be displayed to the visitor – and the climate impact is obviously larger if you are going to send a website from Copenhagen to Singapore than if it is just being shown locally. Nor do we know what time of day the page is being downloaded (the carbon impact is lower at night), or if the access points, i.e. computers and routers that send your website around the Internet, use green energy.

Therefore, we estimate a page based on the size measured in megabytes, abbreviated to MB. This is not a term that we normally go around talking about but in this context it is the most tangible thing to get to grips with.

The smaller the page size, i.e. the smaller the data volume, the smaller the carbon footprint – because less energy is used in the form of power.

We use Google Lighthouse

Google has a solution called Google Lighthouse, which is based on the size of a page. The calculation gives a quick overview of how large the page you are testing is, for example the landing page of your website, and how much potential there is to optimise it to be more energy-friendly. That is what we call overhead or waste. The calculation also shows how little space your page can potentially take up if optimised.

We analyse overhead by looking at the potential to optimise:

  • Image optimization
  • Image size optimization
  • Hidden images and graphics
  • Stylesheets unsused
  • Stylesheets optimization
  • Javascripts duplicated
  • Javascripts unsused
  • Javascripts minification
  • Using old javascripts
  • Compression of files

Video files are measured in the analysis, but it is not possible for the calculator to specify how much a file can be optimised. The calculator only includes videos in MP4 format, and the calculation is based on the full size of the video, no matter how large or small a part of it is downloaded.

We also present the Google Lighthouse score and show the following points:

  • Performance
  • Accessibility
  • Best Practices
  • SEO

Our scale – our approach

Today there are no defined standards or guidelines for how much space a website can reasonably take up. Based on our experience, we recommend:


Over 1 MB - Too heavy
Below 1 MB - Acceptable
Below 500 kB - Good
Below 250 kB - Very good

Is your website hosted using green energy?

We use The Green Web Foundation. Here you can see solutions documented to be hosted with green energy. If you can't find your provider in the database, contact them. Because even if your solution is not registered with the Green Web Foundation, it may still be hosted with green energy.

Our analysis site is the first step – but should not be used alone

The analysis site provides a quick “temperature check” of, for example, how much space your current landing page takes up and how much it can be optimised. With that information, you can discuss with your website provider what they can do.

Order a health report

You can ask us to prepare a health report. Here we carry out an in-depth analysis of your landing page and five sub-pages so that we are clear about what exactly is taking up space on your website. Then we identify the potential to optimise it by looking at the concrete measures that can help minimise your climate impact. We also carry out a benchmark analysis where we look at your landing page compared to five other pages you specify. The analysis is done by analysis and web consultancy TypoConsult, which is responsible for

Order a health report

How much space should a website take up?Energyfriendlyweb

There is no single answer for how much space a website should take up. However, the smaller it is, the less power it will consume. The numbers below can be used indicatively.

Over 1 MB
Too heavy
Below 1 MB
Below 500 kB
Below 250 kB
Very good

Source: TypoConsult