We Audited the Websites of 18 Businesses That Sell Sustainability

After our July study of 100 UK small-business websites, we kept wondering about one group in particular: businesses whose actual product is sustainability. Refill shops. Net-zero consultants. B Corp advisers. Solar and heat pump installers. If anyone’s website walks the talk, it should be theirs.

So in August we audited 18 of them - eco product brands, sustainability service firms, and green trades from around the UK - with the same method as the study: our crawler measuring real data transfer, co2.js converting it to grams of CO₂e per view, and a hosting check against The Green Web Foundation’s directory.

One honest caveat before the findings. This wasn’t a random sample - we picked the 18 by hand, and we deliberately included sites that looked heavy alongside ones that looked lean. So you won’t find “X% of the sector fails” claims here; the group was chosen too knowingly for that arithmetic to mean anything. What the sample is good for is contrast: the gap between the best and worst of these sites is enormous, and the patterns behind it repeat.

The scale ran from A+ to F

The lightest site in the group - a B Corp certification adviser - rated A+ at around 0.04 g of CO₂e per view. The heaviest service firm - a net-zero consultancy - rated F at over half a gram per view, more than ten times as much, with 97% of the weight in photography. Both businesses advise other companies on measuring and reducing footprints.

That pairing is the whole finding in miniature. Selling sustainability tells you nothing about a website’s footprint, in either direction. Some of the leanest, most carefully built pages we’ve measured anywhere belong to this sector - and so do some of the heaviest.

Pattern one: the lightest sites are exercises in restraint

The A-band sites in this group shared a look: modest, well-compressed imagery; a couple of font weights; no sliders, no autoplay, no third-party widget drawer. The same lesson our study found when MOT garages turned out to be the most carbon-efficient sector in British small business: restraint beats polish. The difference here is that these businesses presumably chose the restraint - and it reads as considered rather than plain, which is worth knowing if you’ve been told a sustainable brand needs a cinematic website to be taken seriously.

Pattern two: when a site failed, it was almost always the photography

Eight of our 18 rated D or worse. In six of those eight, imagery was the overwhelming cause - between 72% and 99% of everything the page transferred. Beautiful photography, sincerely chosen, uploaded at whatever size the camera produced and never resized, recompressed, or converted to a modern format. One homepage shipped over 7 MB of photos on every single visit.

This is the cheapest problem in web sustainability to fix. The same pictures, properly sized and served as WebP or AVIF, are routinely a tenth of the weight with no visible difference - a day’s work that usually moves a site two grades or more.

Pattern three: the other failure is invisible

The two remaining failures had light imagery and heavy everything else: JavaScript was 59% and 66% of their page weight - page-builder scripts, widgets, apps - plus hundreds of kilobytes of web fonts, most of which never render. You can stare at a site like this in a browser and see nothing wrong, which is precisely why it happens: the weight lives in things nobody can see. It only shows up when you measure, which is rather the theme of this sector’s own advice to its clients.

Pattern four: green hosting rescued nobody

Half of the failing sites already had verified green hosting. It genuinely helps - renewable-powered infrastructure cuts the emissions of every byte served - but it cannot compensate for serving five times too many bytes. This matches the “green hosting mirage” from the July study: green infrastructure paired with a heavy page is the most common shape of well-intentioned failure on the UK web. Lighten first, then re-host.

The gap isn’t hypocrisy

Here’s the kindest and, we think, truest reading of the eight failures: nobody ever showed these businesses the number. They scrutinise suppliers, audit packaging, and measure operational carbon - and then commission a website the way everyone does, on look and price, because web procurement has never included a weight budget. The founders in this group who’d have rejected a plastic mailer without a second thought had no reason to know their homepage shipped 7 MB of photographs.

Which means the fix is the same one this sector applies everywhere else: measure, then decide. Run your site through our free carbon audit - it takes a few seconds, there’s no signup, and you’ll know which pattern you’re in. If the answer stings, the practical fixes are in our sustainable web design guide, and most of them also make the site faster - which, for a business whose customers are actively checking claims, is the rare fix that pays for itself twice.