It will be very interesting to see some real world numbers.
Can't tell you about i-Pace, but I can tell you about Tesla.
I have P90D (2 years old). The 90 range are "smaller than that" batteries, whereas the 75 and 100 are "actually about that" size. So assume my battery is a few kWh smaller than 90.
My realworld range on 100% charge is 220 miles. A non-Performance model gets a few more miles than that. That's around 75 MPH on motorway on a nice warm day. if I hit 50 MPH traffic for part of a journey, or roadworks, then that will give a boost to my range. I like to leave around 20 miles for "comfort", and if I have a journey more than 160 miles I charge to 100% (for that "can you just pick up X" phone call from Wife
or a detour, or foul weather etc.). Daily I charge to 90% - there is no evidence of significant battery degradation and that's the "daily setting" the car came with. There is evidence that charging to 70% will prolong battery life, but not in the timescale that most people will own the car, and not enough to worry about. 100% charge, OTOH, should be "charge and then drive". But even then I am not anal about it.
In winter range is less, but not dramatically so. The real problem is a cold soaked battery (and Jag heat-pump arrangement may fair much better). The worst scenario is the travelling-salesman who stops for an hour at each location; in that time (at 32F/0C, or colder) the battery will get cold again. Limited regen when starting off and a huge "energy penalty" to get battery, cabin, and so on back up to "best operating temperature" eats into range. If I pre-condition the car (on "shore power") before I leave, and then have a simple, long, highway journey the range loss is perhaps 10% in winter.
Torrential rain is far worse for range than cold (although "cold" here is 32F/0C and not "40 below"
For folk trying to guesstimate range (I don't think the manufacturer figures are much use; Tesla are optimistic (standard government figures), Bolt seems to have significantly underplayed its range capability - Nope, I dunno why either), personally I would be waiting for someone to drive it and properly log the energy use at a number of constant cruising speeds, rather than comparing manufacturers figures at all.
A Better Route Planner
may of interest to folk guesstimating range. That site has recently changed the "Pick a model" from a drop down list of Tesla-only models, to having to, now, first select the Brand (only Tesla in the list just now) so I reckon they are planning to add i-Pace soon. I figure that the Tesla S or X 90 are going to be "similar" to the i-Pace, so that would probably do as a rough-guess.
You can choose a model, and "invent" a journey. You can then see how much battery used up, and from that figure out real-world-range. The site has a huge amount of real-world data collected (for Teslas), so the figures are really accurate (my real-world is about 1.5% different to the prediction), so easy enough to compare Model S, X and 3 for the same journey, and trying 10%, 20% whatever "over" / "under" the speed limit.
UK is not the same as USA in the sense that we don't "drive across the country", so my exceeds-range trips are mostly out-and-back in the day, but something between 220 max 100% range and 300 miles. For me I just stop to get enough juice to complete the journey home. That's not the same as hopping between Superchargers right across the country, of course, but the STATS I have for my car suggest that if I had 350 mile range I would never have a journey that needed charging, and at 300 mile range "almost never". As it is I charge [i.e. away from home] on one or two days a month. I have the benefit of Supercharger network of course, and it is spot-on for doing the job. Park, plug in, walk away. Whilst having a coffee/whatever then check the Charge on the phone APP. Walk back, unplug, drive off.
By comparison the (current) public charging in the UK is utterly hopeless. Myriads of different companies, all with their own APPs, many of which require sufficient money on-deposit before you charge, and if I look at Plugshare
something like 25% of the sites in my area have at least one user-report in the last month of "could not charge". Broken pump is not uncommon, and time-to-fix is far longer than is reasonable.
Typically only one or two pumps at each site, all relatively slow, so high chance of Broken or Occupied (and if occupied, given the slow charge rate, then "for some time"). CCS is coming, but of course it takes time (and money ...) to rollout a decent number of stalls nationwide.
The slow-charging public network is absolutely fine if, for example, shopping if I can plug in for an hour (if using CHAdeMO) or several (if using Type-2). I reckon I have never had a public charging experience that took less than 5 minutes to get connected and disconnect. Frequently they involve me phoning the company and getting them to remote-start the charge (because APP won't work or somesuch), so "overhead" time can be 10 minutes - that would have already got me 20% charge at Supercharger ...) . Things can only improve ... but it really needs to be just like the Tesla experience (or, for that matter, the Gas experience - arrive, park, pump, pay, leave
) so I hope fast-CCS will deliver just that.
All the best to Jag and the i-Pace. The world needs as many credible players as possible. My only disappointment with Jag is the 20K units per annum limit, which I assume is a battery availability limit, and that's going to be the same for all other Marques until the battery industry has some Goliath sized factories of their own.