How green is your web page?

March 6, 2008 10:03 pm | 29 Comments

Writing faster web pages is great for your users, which in turn is great for you and your company. But it’s better for everyone else on the planet, too.

Intrigued by an article on Radar about co2stats.com, I looked at my web performance best practices from the perspective of power consumption and CO2 emissions. YSlow grades web pages according to how well they follow these best practices. What if it could convert those grades into kilowatt-hours and pounds of CO2?

Let’s look at one performance rule on one site. Wikipedia is one of the top ten sites in the world (#9 according to Alexa). I love Wikipedia. I use it almost every day. Unfortunately, it has thirteen images in the front page that don’t have a far future Expires header (Rule 3). Every time someone revisits this page the browser has to make thirteen HTTP requests to the Wikipedia server to check if these images are still usable, even though these images haven’t changed in over seven months on average. A better way to handle this would be for Wikipedia to put a version number in the image’s URL and change the version number whenever the image changes. Doing this would allow them to tell the browser to cache the image for a year or more (using a far future Expires or Cache-Control header). Not only would this make the page load faster, it would also help the environment. Let’s try to estimate how much.

  • Let’s assume Wikipedia does 100 million page views/day. (I’ve seen estimates that are over 200 million/day.)
  • Assume 80% of those page views are done with a primed cache (based on Yahoo!’s browser cache statistics). We’re down to 80M page views/day.
  • Assume 10%, no, 5% of those are for the home page. We’re down to 4M page views/day for the home page with a primed cache. Each of those contains 13 HTTP requests to validate the images, for a total of 52M image validation requests/day.
  • Assume one web server can handle 100 of these requests/second, or 8.6M requests/day. That’s six web servers running full tilt year-round to handle this traffic.
  • Assume a fully loaded server uses 100W. Six servers, year-round, consume 5,000 kilowatt-hours per year or approximately 500-1000 pounds of CO2 emissions.

I think this is a conservative estimate, but there are a lot of assumptions above. And six servers doesn’t sound like a lot. 5,000 kilowatt-hours is a drop in the bucket if you look at data center power consumption. But this was just one rule on one page on one site. Think about the impact of not gzipping, not minifying JavaScript, wasteful redirects, and bloated images. If we extrapolate this across all the performance rules across all sites the numbers are much bigger.

Make your pages faster. It’s good for your users, good for you, and good for Mother Earth.

-Steve

29 Responses to How green is your web page?

  1. [...] Steve Souders, the Web performance chap, has been inspired to calculate how green your website is based on the correlation between fast pages and energy: [...]

  2. [...] Steve Souders, the Web performance chap, has been inspired to calculate how green your website is based on the correlation between fast pages and energy: [...]

  3. Just think how much we’ll save if you turn off and never use your computer again! Do it for mother earth!

  4. [...] High Performance Web Sites :: How green is your web page? Writing faster web pages is great for your users, which in turn is great for you and your company. [...]

  5. Client-side Javascript is another big waster, especially for “widgets” or other components that process and display the same information on dozens if not hundreds of clients instead of doing the work once on the server. I shudder to think how many pounds of CO2 are traceable to obnoxious Flash ads burning CPU cycles in browsers.

  6. Great intellectual exercise! To get a true accounting of the total cost, you’d have to take into account the energy used for lights, PC power, etc. to re-factor and then test new greener versions of existing pages. Even after a complete accounting, I can’t help but think the total amount saved on page views is minuscule when compared to the bandwidth taken up by iTunes, BitTorrent, the major TV networks and others.

  7. Steve Souders asks: “How green is your web page?”…

    Steve Souders, my Velocity conference Co-Chair and author of High Performance Websites, gave me permission to repost this great analysis: How green is your web page? Writing faster web pages is great for your users, which in turn is great……

  8. [...] your pages faster. It’s good for your users, good for you, and good for Mother Earth. — Steve Souders March 8th, 2008 / link / Tags: green computing, webdesign ← previous [...]

  9. Steve Souders from Yahoo! blogs about Green Web Pages…

    Steve Souders from Yahoo! posts up a story entitled How green is your web page? This is the very kind of thinking we need to see more of within the industry.I thought this would be thought provoking enough to be of interest to members that operate…

  10. Want to stop Global Warming? Just follow 14 simple rules…

    Steve Souders, author of the YSlow 14 rules for high performance websites did some back of the envelope…

  11. Want to stop Global Warming? Just follow 14 simple rules…

    Steve Souders, author of the YSlow 14 rules for high performance websites did some back of the envelope…

  12. [...] Steve Souders, author of the YSlow 14 rules for high performance websites did some back of the envelope calculations on the carbon footprint impact of not adhering to some of the rules. High Performance Web Sites :: How green is your web page? [...]

  13. [...] Souders, the Web performance chap, has been inspired to calculate how green your website is based on the correlation between fast pages and energy: Intrigued by an article on Radar about co2stats.com, I looked at my web performance best practices [...]

  14. [...] More here…. [...]

  15. [...] Souders stellt in seinem High Performance Website Blog die These auf, dass schnelle und schlanke Webseiten nicht nur gut für die Benutzer und deshalb gut [...]

  16. [...] Google Would Save 750 Megawatt-hours a Year How green is your web page? CO2 Stats [...]

  17. How To Improve Site Conversion, Minimize Google Ad Cost, And Reduce Your Carbon Footprint…

    With Google’s recent announcement about page load time influencing Quality Score, now is a good time to discuss site speed. Speed matters. People rate snappy, responsive sites as more usable, even when the user interface itself doesn’t change. If yo…

  18. [...] High Performance Web Sites :: How green is your web page? (tags: Environment sustainability design useful) [...]

  19. Though one could argue that turning on gzip uses more CPU, which in turn requires more power. Might be useful to add some tested numbers to this. Let me see if I can test this at some point.

  20. [...] green is your web [...]

  21. erm 100w per server ?? bit more than that I would suspect.

    And increasing performance of a site will tend to increase the power required

  22. @Philip Tellis: Nothing says you have to gzip items on the fly. Gzipping once and then serving hundreds of thousands to millions of times should be a pretty obvious gain.

    @Noone (3): The difference between what you’ve said and what Steve said is that Steve’s suggestions don’t impact functionality. Turning off your computer limits productivity and usefulness. Steve’s ideas saves you servers while keeping your site just as functional as it was before, in fact, it’s better for your end users.

  23. Steve, I’m sure it is easy to use us as a popular example, but there’re few more issues that would have to be covered:

    a) We serve user-provided content, and we have to take it down from time to time. Some of it has to be taken down simply because it is vandalism, sometimes it has to be taken down because of legal reasons. That means we may want to have somewhat more control for data invalidation and purging.

    b) Our content is cached in multiple layers, and by having to replace all cached documents because of single image change we trade one caching efficiency for other caching efficiency.

    c) Revalidation of hot content is probably the cheapest possible operation in webops, and single server can handle multiple thousands of requests like that a second, what reduces the carbon tons.

    And really, we think about bits like that. Actually, we built Wikipedia with ‘somewhat smaller’ budgets than Yahoo or Google or anyone in vicinity did. It is a non-profit operation after all.

    We constantly follow our access patterns, and adapt our caching and performance layers to them. Great to know you’re poking these things too – I guess we can meet up at Velocity and discuss more.

  24. [...] High Performance Web Sites :: How green is your web page? Connection between environment and site speed (tags: environment speedupyoursite performance) [...]

  25. [...] Green Scene Hits Your Code March 20, 2008 8:08 am latoga Technology Ramblings Since my mind is on efficiency this morning (see previous post about Facebook) I wanted to share an interesting blog posting I’ve had open in a browser for a few weeks now.  Steve Sounders, web performance guru from Google and previously Yahoo, posted some interesting thoughts on how green is your web page? [...]

  26. [...] How Green is Your Web Page?   « My del.icio.us bookmarks for March 15th through March 16th |   [...]

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  28. You have some great point in there but alot of guess work if you can pull out some real facts then send them to wiki im sure they would change to catched images instead.

  29. I am all for more efficient web pages for many reasons. However, this is environmentalism and green IT gone amuck. The things we attribute to greening of IT is astounding. Having said that, there is admittedly a weak causal link in that if web sites were more efficient, you would in theory need fewer web site instances and physical hardware. I would suspect though, that the savings would be much more substantial if the bloatware in applications was addressed.