Hi. Your real-world range will most likely be below 281 miles. It might be somewhere between 250 to 270 miles. You can actually calculate this from your lifetime Wh/mi number. On the touchscreen, go to "Controls > Trips", and read your lifetime Wh/mi number. The 100 kWh battery has 98,400 Wh usable capacity when new. Let's say your lifetime efficiency is 370 Wh/mi. That means your real-world range when the car was new would be 98,400/370= 266 miles.
In case you want to compare your real-world range to other people, you can open this page and find your car model in cell B96 (scroll down to row 96). Here you can see that 3 people who participated in this survey have entered their lifetime Wh/mi number for the Model X 100D. Their average is 391.6 Wh/mi which means 251.3 miles real world range when the car was new. However, they are from mainland Europe. Because of the cold climate there compared to the UK, your lifetime Wh/mi number should be better (lower) than 391.6 Wh/mi unless you usually drive at high speeds.
They will get rid of the 351 miles number shown on the UK design studio here and replace it with something like 279 miles in September 2018. The EU has been working on fixing this since 2012 and all they did to fix it was to copy what the USA is doing.
Hi Troy
I really appreciate your in depth reply to my question and showing me how to calculate my wh/mi. As soon as it gets light this morning that will be the first I do.
As each day goes by I am always learning something new about my Model X completely different to my Merc ML350 straight forward to drive and takes no time at all to get used to. I have been driving 47 years and this is the first car that is taking me the longest to get used to drive with all the new technology.
Once again Troy I really appreciate your reply in getting me to understand this range issue.
Where I am in Basildon there are not too many people to talk about the issues with the Tesla so it’s really handy being able to get the answers to questions through the TMC
Thanks again