Homepage emissions: UK Councils

The results

The average emissions from a Council homepage are 0.62g (median of 0.45g) which is worse than an average website (0.5g). Overall, Councils are doing OK. The top and bottom 10 websites are given here with the full list below.

Top 10 lowest emissions

Top 10 highest emissions

Why should councils care?

Each visitor may only produce a few grams of CO2 emissions but when taken over time - and over the number of visitors - that can soon add up. For instance, if your page generates 1g of CO2 per visit and you get 10,000 visitors a month that works out at as much CO2 as boiling water for 5,700 cups of tea a year.

Aside from the environmental impact of large websites, there is also the impact on your visitors who are on limited data plans. A single visit to a 30MB homepage (12g of CO2) would use an entire day's worth of data for someone on a 1GB monthly plan. Should accessing local government be that much of a burden on the poorest in your community?

How can a council do better?

Don't despair! The worst offenders usually have some very easy things they can do to dramatically reduce their CO2 emissions that most likely don't need the IT department to get involved. The first thing to do is check the file sizes of images you use on the front page. Often there will be a large header image, images in a carousel, or images associated with news items. These are most likely added through a content management system which doesn't optimise the image.

Let's find the largest images on a council website. Firstly we'll open our browser's Developer Tools. In Firefox/Chrome/Edge you can usually press F12 to do this (or find it in the browser menu). Once you have Developer Tools open select the "Network" view and then visit the website. As the page loads it should give you a view similar to below.

In this example from March 2021 we have sorted the view by size of file by clicking on the "Size" column heading. We can immediately see that the page totals 32MB with 30.5MB of that due to images. In fact, 22MB comes from just two images! The reason these two are so large is because they have been added in their full, original, resolutions (6571x2850 px and 5392x3595 px) - despite the fact most people's monitors are much narrower than this - and with no optimisation. If we save and open Luther_and_Mayor_1.jpg with the Photos software on Windows we can shrink it to "Large: Best for viewing" which is still a massive 2449x1633 pixels in size. This immediately takes us down to 596kB but we can do better. Using tinyjpg.com (there is also tinypng.com) we can shrink that further to 383kB - 29 times smaller than the original! We could use the same method to shrink the other 11MB image to 322kB. Just optimising those two images would reduce the page size from 32MB to about 10MB. And optimising the other large images would probably get the page down to under 3MB.

When we originally tested the Hambleton District Council website it was producing over 11g of CO2 per visit and was 3rd worst. We suggested that they optimise three of their images - which they did within 5 minutes - and they reduced their carbon emissions to 1.03g of CO2 taking themselves from 3rd to 177th in terms of highest emissions! So some simple, quick, things can make a huge difference.

Images are one area that can be tackled by those who update a website day-to-day. Aside from images, the other common source of emissions is Javascript/CSS. This will most likely require the council Web Team/IT to remove unnecessary or duplicated libraries and is likely a bigger ask. Do large Javascript frameworks need to be included on every page if it could be done in a few lines of vanilla Javascript?

For more tips, Wholegrain Digital have 17 ways you can make your website more efficient and we have a similar blog post from the #PlanetData2 event in 2020.

The full list

Here is the full list of councils with their CO2 emissions but you can also get this as a CSV file or all the data as JSON. Note that council websites often change with new featured items and this can affect their CO2 emissions so this table is a snapshot.

Where the CO2 emissions are given as "?" no result could be found using the Website Carbon Calculator.