webpagetest.org speeds do not match other testing sites

[doubled]

webpagetest.org is giving our site an average of 7.9 seconds to fully load and 5.4 seconds for start render over the last several months (http://www.webpagetest.org/result/160112_ZN_VG7/ - for a recent report).

However after looking through the threads about slow times I found this resource:

http://www.webpagetest.org/forums/showthread.php?tid=12

After following several of the other resources for testing pages, I am completely confounded. Other sites show our site loading much quicker, even if you count the webpagetest.org repeat view with cached data.

http://tools.pingdom.com/fpt/#!/cLZLQJ/h...oducts.com - loads in 1.7 seconds

https://www.dotcom-tools.com/DetailView....73E9858D:1 - loads in 2.17 seconds

There is an addon for Firefox and Chrome called apptelemetry that is showing our site loading in 1.45 seconds (may be cheating since I am internally connected to the network). However, the other sites are all recording much faster load times.

Can someone help me understand why webpagetest.org is so much slower or if there is an accuracy problem with webpagetest.org? I very much want to get an accurate representation of what our visitors are experiencing.

Thank you,


Dustin