so, just to understand, let's say you got 200 miles on a charge (just saying). ?
It really depent about how you are breaking....if you can forsee the breaking you can awoid using the break pedal and only relay on the motor break (regen).
But if you are forced to break fast you need to use the break pedal (energy lost due to heat).
If you teoretically can drive
200 miles (without breaking at all) - then lets prettend you are driving and some times need to slow down or stop,
then you may only gain a range of 160 miles (without any form of regen)
(my own ICE goes down from 12 km/l at highway to 10 km/l in city - this is a reduction by aprox 15% due to more offen breaking in the city)
Tesla is regenerating kinnetic energy using the motor break (you are lifting the gas pedal, while the motor is runing in reverse as a generator) . I asume that it would be posible to regen up to 70% of the energy if ONLY using the motor breake (the last 30% will still be lost as heat).
if you are in need of breaking faster than the motor break is cable -you will need to use the break pedal together with the motor break - then maybe only 10% of the kennetic energy can be regenerated, wasting 90% of the break energy into heat (mostly in the break discs instead)
Doug_G have mention in above post that a typically regen value of
20% is posible in daiyly use.
I your math this will be:
160 miles + regenerated energy (20% of the 40 miles loss) = 168 miles total range.
How much your energy regen rate will be, really depent about how fast you need to break. If you can forsee the trafic in good time, and having the time to only use the motor break, you might be able to regen more than 20%. if you are waiting until last chance to break (using the break pedal) you may loss more and regen less than 20%. - what the practically max value is for regen, I really can not say, since I do not have a Tesla my self - mayby Doug_G knows ?
fast/offen breaking = less range
slow breaking = more regen, less loss
not breaking at all = max range
BTW: Tesla Model S 160, 240 and 300 miles range has already pre calcuated som breaking in the range - since this is messured as a standard driving pattern - making it posible to compare cars, Model S and roadster are using same pattern as ordenary ICE's cars