Range Anxiety and Efficiency

Our cars give us accurate data to enable us to plan and manage a trip. The cars generally panic too early (which is good), especially when you drive them to areas where they do not know any available chargers. However PlugShare fills in the gaps unknown to the cars (but they will remember after the first use). But it is important to check the last users comments on a plugshare point in the bush, and be especially wary if there have not been any previous users.

There are a couple of bits of equipment to borrow if you don’t already have them.  Spare 19” tyre and rims are available from McCarthy’s Prestige for trips out of the Tesla service area. Also loan adaptors are available if you belong to TOCWA or TOCA and the ones which connect to commercial 3 phase sockets are especially important in the bush.

Trip planners like EV Trip Planner calculate Kwh usage allowing for elevation, passenger load, and temperature (in and out of the car!). However they do not allow for wind which can make a huge difference, so if range is critical an estimate of the wind component in the direction of travel should be obtained. It may be necessary to reduce speed by nearly this wind component to maintain the same efficiency as in still air. The side wind component also has an effect as does rough surfaces. EV Trip Planner allows for AC and heating use from the difference in temperature in and out of the car.

But once en route, a good technique for arriving safely with electrons in the tank (or for some, ensuring no stale electrons are left in the tank), is to ensure there is a buffer of 10kms between projected range and distance to go, by setting the speed appropriately. This could mean driving as slow as 50kph if trying to beat Nullarbor Steve’s 540kms trip in a S85 across the Nullarbor, or if a strong headwind picks up. The buffer may have to be higher if the destination is at a higher elevation, but it can be reduced to 10% of the distance to go to avoid those stale electrons.

Although our cars regenerate power, this is not totally efficient, and a better technique is to try to avoid any regeneration – e.g. slowing down very gradually to a road house, or driving with minimal or zero power output up a hill (using just kinetic energy), then allowing the speed to pick again down the other side (rather than using regen).

Remember that there are more places to charge an EV than fill an ICE, because everywhere that has a kettle has a 10amp GPO socket, which will give 150 kms of range overnight.

If driving a long distance in excess of the range of a tankful of electrons, another consideration is en route charging time. An S85 with dual on board chargers 22kw can charge sufficiently fast to replace the extra electrons used by driving at 110kph.

But this is not true for a single charger S85 as the table below shows, and in fact the most efficient speed in still air is more like 90kph. Also the scenery looks much better and the tyres get less hot if driving in the Top End at this speed (ours reached 3.9bar even at 90kph). In fact there are more blown tyres across the road than kangaroo bodies!

The Dual motor cars are much more efficient, so it may be that the 17Kw charger in these could also replace electrons sufficiently fast to make 110 kph the most efficient speed. I will do some checks on my next long journey.


  11 Kw (single charger) 600 kms drive   76 Kwh full charge  
Speed Wh/kms Travel Time Used Kwh Charge Kwh Charge time Total Time Charge rate Kms/hour Range
110 210 5.5 126.0 51.0 4.4 9.9 48 362
95 180 6.3 108.0 33.0 2.9 9.2   56 422
85 165 7.1 99.0 24.0 2.1 9.1   61 461
75 150 8.0 90.0 15.0 1.3 9.3 67 507
55 125 10.9 75.0 0.0 0.0 10.9 80 608
  22 Kw (dual charger) 600 kms drive   76 Kwh full charge  
Speed Wh/kms Travel Time Used Kwh Charge Kwh Charge time Total Time Charge rate Kms/hour Range
110 210 5.5 126.0 51.0 2.2 7.7   95 362
95 180 6.3 108.0 33.0 1.4 7.7 111 422
85 165 7.1 99.0 24.0 1.0 8.1 121 461
75 150 8.0 90.0 15.0 0.7 8.7 134 507
55 125 10.9 75.0 0.0 0.0 10.9 160 608

Data recorded heading south from Carnarvon in still air.

Now that the AESY group (AEVA sponsored by Synergy) are trying to cover all main roads in WA in a 100kms grid of 3phase sockets, there should be no range anxiety anymore, and EV owners will be able to drive the cars as inefficiently as ICE owners do!

Please contact the AESY member below for the state of negotiations in the particular area.

Richard Chapman              Pilbara

Rob Dean                                 Goldfields

David Lloyd                            Kimberley and Nullarbor and Coral coast

Jon Edwards                          South West

Christopher Jones              Great Southern and Wheatbelt east of Perth

Glenn Elliot                            Wheatbelt north of Perth