What our carbon rating actually means
Our site is rated A by Website Carbon. Here is what that measures, what it does not, and why we put the link on the page.
There is a badge on the PepulBill landing page saying the site is rated A for carbon, and it links to the result rather than to the company that issued it. That link is deliberate, and this post is the longer version of it.
What it measures
Website Carbon estimates the emissions of loading a page: how many bytes are transferred, the energy cost of moving and rendering them, and the carbon intensity of the electricity behind that. Fewer bytes, lower estimate.
It is an estimate and a model, not a meter. We say that plainly because a green claim you cannot interrogate is a green claim you should not trust.
How we got there, which is not complicated
Mostly by not adding images. And when we finally measured the whole page rather than the pictures on it, that turned out to be a smaller achievement than we had been claiming.
The illustrations on our features page are the clearest example. Most sites would use screenshots of the app. Ours are built out of the same design tokens the app itself uses — they are text and coloured boxes, not images. The whole features page loads two image files, and both of them are the logo.
- No screenshot library to download.
- No stock photography.
- No video header.
- Fonts and colours shared with the app rather than a second set for the site.
Every image we did not add is a page that loads on a slow connection in Jaffna. The carbon rating is a side effect of that, not the goal.
What we found when we actually measured
Counting images was flattering us. A landing page load is about 866 KB over the wire, and roughly 87% of that is JavaScript — around 711 KB across ten files, against 40 KB of image and 64 KB of CSS. Saying a page is light because it has no photographs, while shipping three quarters of a megabyte of script, is answering an easier question than the one that was asked.
The A rating is real, and it survives because our host runs on renewable energy: the identical page rates A on green hosting and B without it. But the margin is thin. At 866 KB we are within about four per cent of the A boundary, and when we measured every page, the login screen had already slipped to B.
We now measure this on every build, and the build fails if any page drops below A. That check is in the repository as scripts/page-weight.mjs, and it uses Website Carbon's own numbers rather than our arithmetic, so it cannot quietly disagree with the badge on the page.
We published a claim, then built the tool that could contradict it. It did, immediately.
The part that matters more
A light page is not primarily an environmental achievement. It is an accessibility one. Our customers and their customers are on mobile connections that are not always good, on phones that are not always new, often outdoors, often in a hurry.
A page that loads fast for them is the entire point. That it also scores well on a carbon estimate is a genuine and welcome consequence — but if we had to choose which of the two to optimise for, it would be the shopkeeper standing in a crowd at Nallur with one bar of signal.