Discharging
previous: Charging
In the EPA laboratory it is known that Model 3 uses approximately 26 kWh per 100 hundred miles. Another way of presenting this is to say that Model 3 can travel 3.6 miles per kWh. On the most granular level: 278 Wh per mile is an average consumptive rate*. So, after driving for 325 miles (on the EPA test cycle) the battery will have expended its useful range.
*1,000 W / 3.6 mi = 277.7
As stated, the (EPA) advertised consumption is approximate only and based on an imagined standardized testing loop. In the actual world, what external factors can influence the rate of consumption? The biggies are speed, and temperature. To a lesser extent but still worthy is wind*, road surface condition, and hills may be obvious.
A following breeze blowing can be in your favor but if it’s a headwind then essentially add the component to your vehicle speed across the ground. e.g. if you’re driving at an indicated speed of 70 mph but with a headwind of 15 mph you would combine the two because the vehicle is actually doing the work of travelling at 85 mph but only doing the distance of a 70 mph. Even though Model 3 is very slippery in shape and is tops in class for its low drag coefficient, Model 3 is subject to the laws of physics and that means that as speed increases frictional drag increases exponentially. The difference in energy consumption between 55 mph and 75+ mph is considerable. Don’t worry, the Tesla navigation is quite good and will inform as you progress if your driving experience will result in a range shortfall. It does this by letting you know to adjust your speed (reduction). Choice of speed is the best range extending tool at your disposal should it become necessary.
*Wind affects ICE cars too. You’ve just never given it much thought. Your gas gauge got down to a quarter a little sooner than usual and you stopped for gas. It’s more important in an EV for range planning purposes because ‘refueling’ points are fewer and farther between. This is where ‘range anxiety’ comes from!
Drag friction induced by a layer of snow, slush, or wet roadway surface should be compensated for. Temperature is a player especially cold extremes in which case heat will be necessary for cabin comfort and or battery maintenance*.
*Ice cars do have ample supply of heat which would otherwise be thrown away. The EV must use precious resources to make additional heat.
Hot Climate: You will use HVAC to maintain a comfortable interior space. The battery pack has active conditioning using a coolant loop. It kicks in if the pack temperature exceeds a threshold. This consumes energy although it is a great deal less than the energy used when it is cold out. Lowering the windows disturbs the slippery aerodynamics so if you’re driving faster than 40 mph then it is smarter to have the windows closed and the HVAC on instead.
Cold Climate:You will use HVAC to maintain a comfortable interior space. Using the heater draws about 4 kW. So expect to lose ~12 mile of range for every hour of driving with the heater on. Consider lowering the temperature to 68° F and using the seat heaters instead. Generally, you should expect 15% range loss in average cold <50°F and 30% loss in extremely cold climates < 35°F
If the roads are wet, icy or snowy, this will reduce your range because it increases the friction between the tires and the road surface. BMS limits battery performance if it is cold soaked so in this case the coolant loop can supply some warmth. Model 3 uses recovered waste heat from the motor. If you Supercharge a cold battery, the charge rate will be low. Model 3 can condition the battery before you arrive at the Supercharger. Use the car’s navigation at least 30 minutes before arriving at the Supercharger so that the BMS can act accordingly.
Table of generalized range adjustments (compounding):
MISC
| Elevation | uphill lose 10 miles per 1000′ — downhill gain 4 miles per 1000′ |
| Headwinds | 5 mph to 15 mph -8% to -25% |
| Non aero-wheels | -6% |
| Windows lowered | at highway speed -4% |
| Draft a truck or bus (ill advised) | +15% |
HVAC
| 15° F | -25% at full blast, HVAC pulls about 7.5 kW |
| 32 | -13% pre-heat the cabin if possible and then reduce cabin heat temp and use seat heaters |
| 50 | – 7% |
| 70 | 100% of rated range (HVAC on, but barely in use i.e. vent only) |
| 100 | – 7% |
| 120 | -13% |
SPEED
| 45 mph | +26% |
| 55 | + 8% |
| 60-65 | 100% of rated range (at 70 degrees with minimal HVAC) |
| 75 | – 8% |
| 80 | -26% |
ROADWAY CONDITIONS
| Clear and dry | 100% of rated range |
| Wet roadway | – 2%5 |
| Standing water | -10% |
| Light snow | -15% |
| Heavy snow | -25% |