Pillar five of six
Light on the planet
Every byte a page ships is downloaded millions of times over its life, through datacentres, networks, and phones that all draw power. Lean code loads faster, costs your visitor less data, and uses less energy. Good engineering is also good citizenship.
Bees do not waste a wingbeat. Neither should a website.
Five wins, one habit: ship less. This page practises it, no third party scripts, everything it needs inside one file.
Digitally Driven Growth, Naturally
The physics, honestly
Does a website really have a footprint?
Yes, and it is estimated, not measured. Data moving from a server to a phone draws electricity in the datacentre, across the network, and on the device. The open Sustainable Web Design model translates gigabytes into energy and carbon so the direction of a decision can be seen.1
The honest caveat first: every figure on this page is an estimate from a published model, real values shift with grids, devices, and caching, and the point is never the third decimal, it is the direction. Google's own auditor watches the same direction, Lighthouse ships a total byte weight diagnostic on every run.2 In South Africa the case is double: a coal heavy grid on one side, and visitors paying for every megabyte of prepaid data on the other. Lean is respect, twice over.
See it, do not take our word
What does your page weight add up to in a year?
Set a page weight and an audience, and the model does the yearly arithmetic. Then open the anatomy of a heavy page.
The yearly translator
Methodology, stated in full: Sustainable Web Design model version four as implemented in the co2.js library, roughly 0.30 kWh per gigabyte transferred across datacentre, network, and device, at a global grid intensity of 494 g CO2e per kWh.1 Estimates by design, direction over decimals, and first visits assumed uncached, which overstates rather than flatters.
The anatomy of a heavy page
Two builds of the same page, illustrative by design. Toggle them.
Where lean pays
Every term, explained
What do all these terms mean?
Plain definitions, no jargon left standing. Open any term.
Page weight
The total bytes a page transfers to load: images, scripts, fonts, video, and markup. Lighthouse reports it on every audit as total byte weight.2
Sustainable Web Design model
An open, published estimation model translating data transferred into energy and carbon across datacentre, network, and device shares. Implemented in the co2.js library, which this page's figures follow.1
Grid intensity
Grams of carbon dioxide equivalent per kilowatt hour of electricity. The model's global figure is 494, coal heavy grids sit higher, renewable grids far lower, which is why every output here is an estimate.1
kWh and CO2e
A kilowatt hour is the energy unit on your electricity bill. CO2e, carbon dioxide equivalent, expresses all greenhouse gases as one comparable number.
Green hosting
Hosting powered by renewable energy. It shrinks the datacentre share of the footprint, though the network and the visitor's device still draw from their own grids.
Lazy loading
Loading images and media only as they approach the screen. Content nobody scrolls to costs nobody anything.
System fonts
Fonts already on the visitor's device, zero bytes to use. Where a brand font matters, subsetting and modern formats keep it light, this site carries its three Lato weights in about ninety kilobytes total.
Caching
Storing files on the visitor's device after the first visit so return visits transfer almost nothing. The translator above assumes no caching, deliberately overstating rather than flattering.
Sources, triple verified
Where does this page get its facts?
Each source passed three checks on 22 July 2026: it comes from the supplier, it was retrieved and read, and it is current.
- The Green Web Foundation. co2.js, the open implementation of the Sustainable Web Design model. Version four constants read directly from src/constants/index.js at github.com/thegreenwebfoundation/co2.js: operational and embodied energy summing to roughly 0.30 kWh per gigabyte, global grid intensity 494 g CO2e per kWh, retrieved 22 July 2026.
- Google Chrome team. Lighthouse source configuration, the total byte weight diagnostic, read from core/config/default-config.js at github.com/GoogleChrome/lighthouse, repository updated 20 July 2026.
Figures for South African grid intensity and mobile data pricing will join under the same standard once retrieved from Eskom and ICASA publications, held on the register as item 8.20. Every output above is labelled as the estimate it is.
The next step is small
Where does your site stand today?
Choose two answers. The audit shapes itself around you, and the first finding usually arrives in the first conversation.
Your site today
What matters most
The audit is free, and the findings are yours to keep, whoever you build with next. This page sets no cookies, loads no third party scripts, and tracks nothing. That is the standard, demonstrated.