Plot of vehicle weight vs efficiencies in Watt Hr / Mile
Ways to increase Efficiency
1. Reduce weight. This is probably the best way to go farther and faster. Ever looked in a drag car or road race car? Only the items needed for driving the car and safety are in the inside. This is to reduce weight to a bare minimum.
2. Reduce wind resistance. Air is actually a fluid. Any car or truck moving at speed builds up air resistance quickly the faster you go depending on the shape of the car or truck, and the speed. You may notice that Evs are sometimes streamlined so as to folw through the air using less energy.
3. Low rolling resistance tires. Car tires actually resist rolling to a small degree. EVs often use special low rolling resistance tires. These tires have higher air pressures and may cost a bit more than reugular treads, but will give you increased fuel economy - better gas mpg.
4. Energy Efficiency. One of the big areas of wasted energy is braking. Electric vehicles from large to small are now capturing the energy formely lost in braking. This is called regenerative braking. The energy recaptured may be stored in a battery or ultracapacitor.
5. Engine or motor shutoff. The electric motor is develops its full power at start up. This makes it possible to stop the car often without wasting fuel during idle. Hybrids (except mild hybrids) can use the battery to start the car moving and then use the gas motor as needed.
6. Electric motor efficiency. The electric motor is inherently more efficient than the gasoline or diesel engine which is 30 or 35 percent efficient tops. Electric motors can top 90 or more percent efficiency. GE has recently developed a permanent-magnet electric motor that increases efficiency another 3 to 5 percent.
The Bottom Line: The EV owner-drives saves money and the air is less polluted.
The plot to the left shows
car weight plotted against energy needed per mile (WH/Mi) to drive the car.
The plot shows that the amount of energy used per mile (WH/Mi) increases as the car gets heavier.
For this plot, English units have been used, but the graph would look about the same in SI units.
Electric car efficiency helps modern day electric cars and trucks get the most out of their battery packs. Efficiency gains are made for the most part by lowering weight and resistance to the wind.
The Toyota Prius looks a little different because it is designed and shaped for the lowest practical wind resistance. The Tesla Model S uses an aluminum platform for strength and lowered weight. The BMW i8 PHEV features an aluminum frame and carbon fiber body panels saving hundreds of pounds.
Why Efficiency Matters
Electric car battery packs hold just a fraction of the energy found in the average gasoline tank. Plug in hybrid electric vehicles carry about half as much gas and the hybrid electric vehicles carries a lot of gas and just a little battery pack power.
So, the battery EV and plug in EV can use all the efficiency they can get. The hybrid gets a lot better fuel economy and pollutes a lot less when made efficient.