Having spent some time travelling more than 300km at a time in South Africa, these are my top 10 factors that affect range from a practical point of view. The efficiency of EV's are improving daily by the type of motors, drag reduction, battery chemistry and motor decoupling. This list applies to all Ev's.
1. Towing
Expect range to decrease by half.
2. Hills, false flats , mountain passes.
The battery simply has to deliver more energy and regen will only replace a fraction of the energy lost.
3. Speed
Pushing a vehicle into air over 120km/hr eats the battery!. It is surprising how efficient the car is below 110km/hr
4. Wind
Again resistance is directly proportional to the strength and direction of the wind. Even a cross wind will severely affect the car's aerodynamics. I have little experience with air density but would imagine better range on the highveld ?
5. Rain
Wet roads increase friction and this is often associated with wind to chew the battery
6. Heating
This is not as big a problem in SA as in cold climates. I recommend seat heating rather than using the heat pump on long distances.
7. Air Conditioning
Heat pumps have made this much more efficient, preconditioning before a long trip can save up to 20 km of range !
8. Road surface
Asphats that are rough increase friction and can drain the battery.
9. Weight
EV's are heavy, momentum = mass X velocity. If one maintains momentum by looking at the road topography ahead you can extend your range significantly. Luggage is therefore not a major factor in inhibiting range ! NB turn the regen or B mode off on a long trip so you can exploit the car's momentum. Hypermiling in an EV has little range gain.
10. Tyres
Obviously correct inflation is important however as long as it is a dedicated road tyre the different brands make little difference. Off road tyres will decrease efficiency by over 20 %
PV Amped
(source: Drive Electric)