I can put a figure on it. A couple of weeks after buying my new Nissan Leaf in 2018, I set out on a range test. Using only Normal mode, no Eco, I drove normally continuously using mainly B roads and known lanes but some short A road stretches, eventually getting within reach of home as the battery was getting low, but conmtinuing on local lopps until reaching the "Urgent Charge Now" dash message, meaning only 10 + 3 miles left to totally empty. At that point I'd covered 162 miles.
Just over a week later I repeated the test but this time driving aggressively. Here in the South East below London speed doesn't come into that since all the roads where speed could be possible are infected with speed limits to the degree that the majority of drivers just convoy at around 40 mph. And on the back lane in the country the nature of them prevents high speeds. I use the same Normal mode and similar routes and as well as using aggressive maximum acceleration I managed to include two twisty climbs to the top of the North Downs. The terminal distance covered at the "Charge Now" point was 146 miles.
Both were warm Summer days, so the loss due to aggressive driving was 10%, but with the gain of a lot of fun doing the second test.
The big loss of course as Danidl says is from driving at speed such as on motorways and i've also tested that to a small degree. The difference in range between cruising at 65 or at 75 is quite dramatic, all out of proportion to the time saved.
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