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Electric car basics – energy, range and costs

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An understanding of their basics is vital to discovering whether pure electric cars may be suitable for you, and what their realistic running costs may be. Let’s look first at charging your car. Most owners mainly use a purpose-built home charger rated at 7kW, or around twice the charge rate of a simple 13 Amp plug charger. With 7kW you can fully charge most cars in around 4 to 10 hours and, with an overnight low-cost tariff, you can maximise savings by setting your charger timer to synchronise with the low tariff hours. Faster charging is available, if you need to charge up on the road, but the costs can be quite high, or more than twice the cost of domestic charging.

 

With a fully charged battery, your driving range will depend on the battery capacity, which will range from the 24kWh on the short-range old model Nissan Leaf to the popular capacity of 40kWh offered in the Renault Zoe and current Leaf, to the 90kWh of the Jaguar I-Pace, and 75kWh and 100kWh of Teslas.  As a rule of thumb, ìofficialî ranges equate to between 5 miles per kWh, for gentle driving in a lighter car, without using heating or air conditioning, but down to 3 miles per kWh or less for a larger and enthusiastically driven Jaguar or Tesla, and even manufacturer quoted ìreal worldî figures tend to be optimistic.

 

As you drive, your total energy consumption will generate a display showing your remaining range, taking into account your driving style and speed, which will be constantly updated as the battery is depleted. You will also find a display showing the equivalent of mpg, as miles per kWh, or kWh per 100 miles, along with a graphic display showing your instantaneous energy consumption, either in figures, or a meter where a needle in the blue sector indicates good economy, and in a red sector, it is bad.

 

Most electric vehicles offer a choice of settings that increase the regeneration effect, feeding more energy back into the battery when you lift off the accelerator, and decelerating the car with increasing intensity. Most offer an Eco mode that limits the engine power output, thus reducing acceleration and speed potential. Nissan’s Leaf has a selectable e-pedal option, where lifting off delivers significant deceleration, rendering the brake pedal near redundant, save for emergencies. Acceleration rates have little effect on fuel economy, and they vary from adequate for normal motoring, up to simply startling! You get a continual stream of power and torque, and the power delivery characteristics of electric drive almost eerily whisk you to higher speeds with no gear changes, and very little in the way of noise.

 

Energy costs are primarily dependent on driving speeds, as most energy is used in overcoming aerodynamic drag and tyre rolling resistance. Other than slowing down, conventional eco driving techniques are less effective. There’s no benefit in easing off early when slowing down, if you’re in a high regeneration setting, whilst the less that you use your brakes, the more energy that goes back into the battery, when you need to slow down for any reason.

 

A realistic figure for home or workplace costs is 12 to 14p per kWh, although this is increasing fast. A small car, that might use 1kWh every four miles, costs 3 to 3.5p/mile. Faster, heavier, cars might only cover two to three miles, and cost 4 to 6p/mile, both compared with 10 to 15p/mile for diesel cars. These are optimum figures though, and energy used to operate climate control in extreme ambient temperatures has seriously negative effects on cost per mile and driving range. Electric vehicle depreciation costs from new are high though, due to the frequency with which cars are updated, but bargain buys are available in low mileage ìnearly newî cars. Depreciation from a brand new car can, however, approach 40 to 50p a mile, and sometimes more, making the energy cost savings of electric power relatively insignificant in the greater scheme of things.

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