Climate friendly speed tests

TL;DR

Speed test loads a lot of data to measure your download speed. Due to the widespread use of speed tests, they contribute significantly to global CO₂ emissions. It is therefore preferable not to use a speed test if it is not really necessary. Should you use a speed test? Then use Internet Speed at a Glance or use Google Fiber.

These speed tests take the least time (and therefore data) to measure the download speed. As a result, they have the smallest ecological footprint (0.30 and 16 grams of CO₂ respectively).

The rule of thumb for determining the carbon footprint of a speed test is:
The carbon footprint in grams of CO₂ is twice the download time in seconds.

Content

1. Why the carbon footprint of a website matters
2. How to get the carbon footprint of a speed test
3. The carbon footprint per speed test
4. The median carbon footprint of a speed test

Why the carbon footprint of a website matters

Web pages and tools that you use on the Internet cost electricity and therefore have a carbon footprint. According to the IPCC, reducing CO₂ emissions is critical for your future.

One of the most popular tools on the Internet are speed tests. Speed tests are that popular that when you Google for "speed test", Google gives you the option to start a Measurement Lab (M-Lab) speed test directly.

Because a speed test loads extra data to measure your download speed, a speed test has a huge impact on the worldwide CO₂ emission. Millions of tons are involved every day.

How to get the carbon footprint of a speed test

To get the carbon footprint of a speed test two things are required:

1. An unambiguous relationship between the size of a download (in Mb) and the carbon footprint
2. A good estimate of the amount of data (in Mb) that is loaded during a speed test

The relation between download size and carbon footprint

Sites as Website Carbon Calculator indicates the CO₂ required for a webpage. By testing multiple webpages it is possible to relate the CO₂ required to the size of the webpage.

The carbon print of a webpage

The carbon footprint of the home pages of the tested speed tests, as measured with the Website Carbon Calculator, are the following (less is better):

1. LibreSpeed 0.03 gram CO₂
2. Fast 0.04 gram CO₂
3. Google Fiber 0.15 gram CO₂
4. Bredbandskollen 0.21 gram CO₂
5. Comparitech 0.22 gram CO₂
6. Measurement Lab (M-Lab) 0.23 gram CO₂
7. Broadband Internet Speed test 0.24 gram CO₂
8. Meter.net 0.27 gram CO₂
9. Internet Speed at a Glance 0.30 gram CO₂
10. Xfinity Speed Test 0.31 gram CO₂
11. nPerf 0.44 gram CO₂
12. SpeedSmart 0.44 gram CO₂
13. Open Speed Test 0.50 gram CO₂
14. Fireprobe 0.51 gram CO₂
15. SamKnows Speed Test 0.66 gram CO₂
16. Which Broadband Checker 0.70 gram CO₂
17. Testmy.net 0.71 gram CO₂
18. Bandwidth Place 0.78 gram CO₂
19. Broadband Speed Checker 0.82 gram CO₂
20. DSLReports 0.82 gram CO₂
21. SpeedOf.me 1.01 gram CO₂
22. Toast 1.23 gram CO₂
23. Speedtest4.php 1.71 gram CO₂
    
24. Cloudflare 1.78 gram CO₂
25. Ookla Speedtest 1.86 gram CO₂
26. RCN 2.15 gram CO₂
27. CompareSpeedTest 3.56 gram CO₂

According to the Website Carbon Calculator the average web page tested produces 1.76 grams CO₂ per page view. Only 4 of the tested speed tests are worse than average.

The relation between download size and carbon footprint

Based on the above carbon footprints and the size of the homepages as measured with the Pingdom Website Speed Test the following is concluded:

1. LibreSpeed: 0.03 gram CO₂, 36.4 kb
2. Fast: 0.04 gram CO₂, 498.2 Mb
3. Google Fiber: 0.15 gram CO₂, 477.4 kb
4. Bredbandskollen: 0.21 gram CO₂, 421.0 kb
5. Comparitech: 0.22 gram CO₂, 422.8 kb
6. Measurement Lab (M-Lab): 0.23 gram CO₂, 430.8 kb
7. Broadband Internet Speed test: 0.24 gram CO₂, 467.1 kb
8. Meter.net: 0.27 gram CO₂, 1.3 Mb
9. Internet Speed at a Glance: 0.30 gram CO₂, 558.2 kb
10. Xfinity Speed Test: 0.31 gram CO₂, 545.7 kb
11. nPerf: 0.44 gram CO₂, 966.5 kb
12. SpeedSmart: 0.44 gram CO₂, 816.2 kb
13. Open Speed Test: 0.50 gram CO₂, 959.9 kb
14. Fireprobe: 0.51 gram CO₂, 837.9 Kb
15. SamKnows Speed Test: 0.66 gram CO₂, 1.1 Mb
16. Which Broadband Checker: 0.70 gram CO₂, 1.4 Mb
17. Testmy.net: 0.71 gram CO₂, 1.6 Mb
18. Bandwidth Place: 0.78 gram CO₂, 1.3 Mb
19. Broadband Speed Checker: 0.82 gram CO₂, 2.7 Mb
20. DSLReports: 0.82 gram CO₂, 1.1 Mb
21. SpeedOf.me: 1.01 gram CO₂, 1.3 Mb
22. Toast: 1.23 gram CO₂, 2.2 Mb
23. Speedtest4.php: 1.71 gram CO₂, 3.6 Mb
24. Cloudflare: 1.78 gram CO₂, 973.6 Mb
25. Ookla Speedtest: 1.86 gram CO₂, 2.9 Mb
26. RCN: 2.15 gram CO₂, 3.6 Mb
27. CompareSpeedTest: 3.56 gram CO₂, 6.7 Mb

Based on the results above the formule for a trendline is:
Carbon Footprint (in gram CO₂) = 0.53 * size in Mb - 0.02

The estimated amount of data (in Mb) required for a speed test

For a speed test the following formula applies:
Megabits downloaded = Download speed in Mbps * download time in seconds

With a download speed of 84 Mbps (the real download speed provided by the ISP used), it is clear that every second that a speed test is downloading data, to calculate the internet speed, 84 Mbits are downloaded.

1 byte = 8 bits, hence you might state that every second 84 / 8 = 10.5 Megabyte is downloaded.

Hence the formula:

Carbon Footprint (in gram CO₂) = 0.53 * size in Mb - 0.02

might be rewritten as:

Carbon Footprint = 0.53 * 84 * time for downloadtest in seconds / 8 - 0.02

Measuring is knowing

The data used to perform a speed test has recently been measured. In combination with the formula Carbon Footprint (in grams CO) = 0.53 * size in Mb - 0.02, it is possible to directly determine the Carbon Footprint.

The carbon footprint based on the measurement at an advertised speed of 100 Mbps has been added to the list below.

Note that this second measurement is done with an advertised speed of 100 Mbps instead of the earlier advertised speed of 75 Mbps.

The carbon footprint per speed test

The following list gives the estimated carbon footprint per download test.

1. Internet Speed at a Glance: 0.30 gram CO₂ (the homepage is the speed test), measured at 100 Mbps: 0 gram CO₂
2. Google Fiber: 8 seconds ≈ 45 gram CO₂, measured at 100 Mbps: 55 gram CO₂
3. CompareSpeedTest: 25 seconds for the complete test ≈ roughly 9 seconds for the download test ≈ 50 gram CO₂, (Gone)
4. LibreSpeed: 10 seconds ≈ 56 gram CO₂, measured at 100 Mbps: 58 gram CO₂
5. Measurement Lab (M-Lab): 10 seconds ≈ 56 gram CO₂, measured at 100 Mbps: 90 gram CO₂
6. Toast: 10 seconds ≈ 56 gram CO₂, measured at 100 Mbps: 13 gram CO₂
7. Bredbandskollen: 22 seconds for the complete test ≈ roughly 11 seconds for the download test ≈ 61 gram CO₂, measured at 100 Mbps: 90 gram CO₂
8. Meter.net: 24 seconds for the complete test ≈ roughly 11 seconds for the download test ≈ 61 gram CO₂, measured at 100 Mbps: 60 gram CO₂
9. Testmy.net: 25 seconds for the complete test ≈ roughly 11 seconds for the download test ≈ 61 gram CO₂, measured at 100 Mbps: 56 gram CO₂
10. Broadband Speed Checker: 36 seconds for the complete test ≈ roughly 13 seconds for the download test ≈ 72 gram CO₂, measured at 100 Mbps: 113 gram CO₂
11. Open Speed Test: 35 seconds for the complete test ≈ roughly 14 seconds for the download test ≈ 78 gram CO₂, measured at 100 Mbps: 134 gram CO₂
12. nPerf: 70 seconds for the complete test ≈ roughly 15 seconds for the download test ≈ 84 gram CO₂, measured at 100 Mbps: 157 gram CO₂
13. Bandwidth Place: 15 seconds ≈ 84 gram CO₂, measured at 100 Mbps: 83 gram CO₂
14. Which Broadband Checker: 36 seconds for the complete test ≈ roughly 15 seconds for the download test ≈ 84 gram CO₂, measured at 100 Mbps: 97 gram CO₂
15. SpeedSmart: 16 seconds ≈ 89 gram CO₂, measured at 100 Mbps: 109 gram CO₂
16. Fireprobe: 18 seconds ≈ 100 gram CO₂, measured at 100 Mbps: 145 gram CO₂
17. Comparitech: 21 seconds ≈ 117 gram CO₂, measured at 100 Mbps: 157 gram CO₂
18. Ookla Speedtest: 21 seconds ≈ 117 gram CO₂, measured at 100 Mbps: 148 gram CO₂
19. Xfinity Speed Test: 22 seconds ≈ 123 gram CO₂, measured at 100 Mbps: 94 gram CO₂
20. Fast: 23 seconds ≈ 128 gram CO₂, measured at 100 Mbps: 134 gram CO₂
21. DSLReports: 24 seconds ≈ 134 gram CO₂, measured at 100 Mbps: 143 gram CO₂
22. SpeedOf.me: 25 seconds ≈ 139 gram CO₂, measured at 100 Mbps: 184 gram CO₂
23. Cloudflare: 56 seconds for the complete test ≈ roughly 27 seconds for the download test ≈ 150 gram CO₂, measured at 100 Mbps: 122 gram CO₂
24. RCN: 27 seconds ≈ 150 gram CO₂, measured at 100 Mbps (Astound!): 158 gram CO₂
25. SamKnows Speed Test: 28 seconds ≈ 156 gram CO₂, measured at 100 Mbps: 125 gram CO₂
26. Broadband Internet Speed test: No meaningful results
27. Speedtest4.php: No meaningful results

The median carbon footprint of a speed test

To know the median carbon footprint of a speed test we first need to know the median download speed.

According to Ookla the global median download speed for mobile in March 2022 is 29.60 Mbps. So it is probably better to estimate the carbon footprint based on 30 Mbps in stead of 84 Mbps.

This results in the following formula: Carbon Footprint = 0.53 * 30 * time for downloadtest in seconds / 8 - 0.02 = 1.99 * time for downloadtest in seconds - 0.02

1.99 is almost 2 and 0.02 is that small compared to 2 that it is safe to state the following rule of thumb:

Based on the rule of thumb mentioned these are the global median carbon footprints, based on the download time and the formula mentioned above:

1. Internet Speed at a Glance: 0.30 gram CO₂ (the homepage is the speed test)
2. Google Fiber: 8 seconds ≈ 16 gram CO₂
3. CompareSpeedTest: 9 seconds ≈ 18 gram CO₂
4. LibreSpeed: 10 seconds ≈ 20 gram CO₂
5. Measurement Lab (M-Lab): 10 seconds ≈ 20 gram CO₂
6. Toast: 10 seconds ≈ 20 gram CO₂
7. Bredbandskollen: 11 seconds ≈ 22 gram CO₂
8. Meter.net: 11 seconds ≈ 22 gram CO₂
9. Testmy.net: 11 seconds ≈ 22 gram CO₂
10. Broadband Speed Checker: 13 seconds ≈ 26 gram CO₂
11. Open Speed Test: 14 seconds ≈ 28 gram CO₂
12. nPerf: 15 seconds ≈ 30 gram CO₂
13. Bandwidth Place: 15 seconds ≈ 30 gram CO₂
14. Which Broadband Checker: 15 seconds ≈ 30 gram CO₂
15. SpeedSmart: 16 seconds ≈ 32 gram CO₂
16. Fireprobe: 18 seconds ≈ 36 gram CO₂
17. Comparitech: 21 seconds ≈ 42 gram CO₂
18. Ookla Speedtest: 21 seconds ≈ 42 gram CO₂
19. Xfinity Speed Test: 22 seconds ≈ 44 gram CO₂
20. Fast: 23 seconds ≈ 46 gram CO₂
21. DSLReports: 24 seconds ≈ 48 gram CO₂
22. SpeedOf.me: 25 seconds ≈ 50 gram CO₂
23. Cloudflare: 27 seconds ≈ 54 gram CO₂
24. RCN: 27 seconds ≈ 54 gram CO₂
25. SamKnows Speed Test: 28 seconds ≈ 56 gram CO₂

With 0.30 gram CO₂ Internet Speed at a Glance has clearly the least carbon footprint (a factor of 100 less than the median speed test).