Driving conditions, as well as driver skills and habits, have a large influence on energy use. Tesla Motors have detailed some of these relationships in several of their blogs. The nominal EPA range of the Tesla Roadster is currently 390 km (245m). That this range is not fiction was demonstrated 2009 and again 2010 in a rally in Southern France. Carefully driven on mountainous backroads the range to empty would have been around 450 km. Notes on this event in French or English can be found on my Links Page. The roadster shown in April 09 to interested parties in Zurich was driven about 320 km without recharging from Munich to Zurich and had some reserves left. Another Tesla Roadster was driven last winter from Zurich to St. Moritz, across the Julier Pass, with snow tires and some heating. Only 210 km, but climbing also from 400m to 2300m. Considering that this is a close to 3 hours drive with a fair stretch on a winding mountain pass road, not everybody would (and should) drive any further without a solid break. With the graphs and data shown in a Tesla Motors blog and converted here to km, we can estimate the approximate consumption for a trip e.g. from Zurich to Geneva (281km of motorway): 150 km at top legal speed (120km/h) at 200 Wh/km: 30 kWh, then 100 km at reduced speed, say 80km/h at 137 Wh/km: 13.7 kWh and 30 km town traffic at 90 Wh/km: 2.7 kWh.Grand total for this trip: 46.4 kWh.†
In reality I would expect traffic conditions to slow this trip below the speeds assumed above, leaving some additional reserves. At lower speeds the stated range can become also considerably larger than EPA standard ranges as demonstrated in Australia where a record 501 km was driven on a single charge. These relationships are partly very different for conventional cars. Their mileage tends to worsen notably at speeds below about 80 km/h and in urban traffic. Most estimates of potential fuel substitution ignore this effect and overestimate consequently the call on additional electricity.
Clearly these ranges cannot satisfy as yet regular motorway speed long distance drivers, but show how close we are to widely usable electric vehicles: A lot closer than many still believe.†Note that the Tesla Roadster achieves much larger ranges than most other purely electric vehicles and electric vehicle prototypes, shown so far. Tesla Motors have built a highly efficient drive train - by no means an easy task. The technical achievement is respectable. Tesla Motors have won a leading position in this technology. Of course technology does not stand still. Batteries and control electronics, as well as the science surrounding electrochemical cells will evolve relatively fast. Also Tesla's new Model S demonstrates remarkable progress. I outlined my views on future trends here. Of course range on a single charge is not the only issue. It is also important to know where and how fast a car can recharge.
The original model S achieves usually more than 400 Km under ordinary mixed driving conditions in Switzerland and its latest version (P100D) will surpass that again with practical ranges towards 500Km (613 Km, NEDC cycle test).†