Calculating costs: electric or internal combustion vehicles

Weigh the “pros and cons” of electricity versus gasoline and diesel.

As the shift to mainstream electric vehicle acceptance draws closer, more motorists are weighing the pros and cons of electric versus gasoline and diesel. While internal combustion engines (ICEs) still have many advantages, electric vehicles are simply cheaper to run per mile.

To prove this point, Jaguar South Africa sent one of its experienced driving instructors on a week-long mission to record and report the electricity consumption and cost per km (R/km) of a fully electric vehicle. Jaguar I Pace in a variety of real-world driving environments. To compare these costs to those of a vehicle equipped with a traditional internal combustion engine, the brand has developed a simple formula.

From motus.cars, supported by Motus Nissan (formerly Imperial Nissan):

To fill

The costs of filling EV batteries and the ICE fuel tank may not be relevant to the R/km comparison, but it’s worth knowing that EVs win this fight hands down.

Charging a completely depleted I-Pace at your home will cost less than R200 based on current municipal rates in Gauteng. Filling the tank of a similarly sized ICE SUV will cost four times as much, if not more.

It must be remembered that the cost of filling an EV or ICE vehicle means nothing without considering the maximum range of both. Jaguar claims a range of 470km on a full charge, but in the real world the actual range is closer to 400km. Most petrol and diesel vehicles can travel farther on full tanks, but it’s the cost per kilometer that’s most important.

The effect of different driving environments

While ICE vehicles suffer from slow, stop-start traffic, it is in this environment that electric vehicles have an advantage. ICE vehicles will continue to consume fuel whether in motion or not, while EVs will consume almost no electricity when stationary or when slowly moving through bumper-to-bumper traffic.

“During my week with the I-Pace, I deliberately spent my morning and evening journeys in as much traffic as possible. The on-board computer recorded an average of 22kWh/100km during heavy congestion , which, when calculated against my home electricity rates, equates to around 44 cents per kilometre,” said Andrew Blane, Lead Instructor, Jaguar Land Rover Experience Johannesburg.

“I originally expected better results due to the fact that the I-Pace uses almost no power when it’s not moving, but at such low speeds it’s not capable recover a lot of energy through regenerative braking. Electric vehicles use momentum to put some charge in their batteries, but in slow-moving traffic there is not enough kinetic energy to harness.” Blane added.

Unlike ICE vehicles, which are more efficient when running at low rpm at high speeds, EVS are less efficient at constant speeds on the open road. Even so, the I-Pace returned favorable power consumption and R/km figures in Andrew’s test.

Hit the open road

The energy that an electric vehicle uses to drive at high, constant speeds varies significantly with average speeds. On the highway at 120 km/h, the I-Pace is less efficient. Extended periods on the throttle without regenerative braking resulted in an average power consumption of 24 kWh per 100 km, which still equates to a cost per kilometer of just 48 cents.

Extra urban

Electric vehicles thrive in environments with a balance of relatively high speeds and frequent braking, such as along major thoroughfares in South Africa’s urban centers or weekend jaunts around the country. The I-Pace’s trip computer recorded averages as low as 17kWh/100km in these conditions, which equates to just 34 cents per kilometer.

Average

Most motorists drive on a variety of roads and driving environments, making fuel and electricity consumption averages the most important numbers to use as bases for comparisons between ICE and EV. For the Jaguar I-Pace, that means an average of around 22kWh/100km, which equates to around 44 cents per kilometer when charged at home and using the national household average of around R2 per electricity unit.

ICE in comparison

The cost per kilometer of petrol and diesel vehicles is an ever-changing calculation given the volatility of fuel prices. Fuel prices also vary by location, with coastal fuel prices being slightly cheaper.

For example, even fuel efficient vehicles that consume 5.0 liters per 100 km cost R1.04 per kilometer to drive and this rises to R4.17 per kilometer in a vehicle that uses 20 liters per 100 kilometres.

By comparison, at the efficient end of the scale, an electric vehicle using 15kWh per 100km costs only R0.30 per kilometer to operate and R0.60 per kilometer at the high end of the scale when it consumes 30 kWh/100 km. This rough calculation makes an electric vehicle at least three times cheaper to run, but that figure only improves on ICE vehicles that consume more fuel than 5.0 liters per 100 km.

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Kevin A. Perras