Web Devs of Devrant, i have a question for you!

How to you efficiently test a website speed?
Sure i know about googles page insight, GTmatrix and all the other "free" testing tools.
But im more interested in a tool i can make run multiple times, and then get a avg (or at least some kind op spreadsheet) showing the time it taken to load - and the different parts.

Say i want a test to run 1 time every 5 min, 20 times - then get data for all those. Any tools that can make such data available to me?
Or should i look at some other tools?