And how does that compare with refuelling a conventional car?

Buyers considering an electric car for their next purchase may ask themselves whether an EV will be cheaper to run.

Unfortunately, there’s no clear-cut answer – unless ‘depends’ is clear enough…

EV owners should see lower running costs overall, but the answer ultimately ‘depends’ on factors that are not set in concrete.

Can you draw power from the solar panels on your roof to recharge the car, for instance? That will vary from person to person according to whether the vehicle owner can charge the car at home during the day (taking public transport to work) or whether the car can be recharged at night from a domestic battery that is itself recharged from the solar panels during the day.

As an alternative, the car itself may be the battery that powers home appliances at night, assuming it has been fully charged during the day without driving anywhere in the meantime.

Conventional wisdom suggests that even recharged from the national electricity grid, an EV can be cheaper to run than a car of similar size, powered by an internal-combustion engine. But how much cheaper (if at all) will vary with the tariff charged by your electricity retailer.

Furthermore, no one knows how prices for power from the grid will rise or fall over the next decade. That will influence the running costs of your EV too. And as EVs hit the road and fewer drivers pay the government a fuel excise, expect the government to find new ways to tax EV owners.

EV Council’s cost calculator

According to an online calculator developed for the Electric Vehicle Council, to recharge a small battery-electric car like the Nissan LEAF or Hyundai IONIC Electric could typically cost $50 a month less than refuelling a petrol hatch.

The beaut thing about the EV Council’s calculator is that you can tailor the settings to suit your personal lifestyle – including the solar panels on your roof, the daily driving distances (separately for weekdays and weekends) and even whether you can charge the car for free at work or from a Tesla Supercharger during the day.

The most expensive peak-hour electricity tariff we’ve seen offered by a retailer is 66.08 cents per kiloWatt-hour (kWh). According to the EV calculator, and even at that rate – without drawing on solar power or a battery – a small EV would still be $47 a month cheaper than its petrol counterpart.

Explaining the maths

The second-generation Nissan LEAF has a 40kWh battery. In WLTP (combined-cycle) testing the LEAF can travel up to 270km between battery recharges.

Taking the LEAF as our benchmark, and a tariff of 0.28 cents per kWh, the Nissan EV would cost $11.48 to recharge from zero to 100 per cent of battery capacity – 40kWh.

That’s the tariff (which is on the back of your electricity bill) multiplied by the LEAF’s battery capacity in kiloWatt-hours.

With the Australian Institute of Petroleum presently reporting petrol pricing of around $150.00 across five capital cities, the cost of running a Toyota Prius for 270km – the same distance as the range for the LEAF – will cost the owner $13.77.

On paper, it’s ‘advantage LEAF’ for running-cost savings. There are a couple of additional points to consider, however.

Firstly, if you recharge the LEAF during peak hour, and your tariff is as high as the figure of 66.08 cents per kWh already mentioned – and that is the worst-case scenario we’ve seen so far – the cost of recharging the LEAF will be double the cost of refuelling the Prius for the same distance.

On that basis it will cost the LEAF owner $26.43 for 270km of range – or the full 40kWh recharge.

On the other hand, of course, the Prius is exceptionally economical in comparison with other petrol-engined cars. A conventional car boasting a combined-cycle fuel economy figure of around 7.0L/100km would be ostensibly using fuel at double the rate of the Prius.

And from a cold start, most 2.0-litre small cars will barely reach normal operating temperature within a 10km journey. Throw in some traffic and unfavourable light sequences and the car’s fuel economy may be no better than 10L/100km.

What can we say, Ken loves a spreadsheet

On that basis, the petrol car’s fuel cost may rise as high as $40 for 270km travelled. This is where the EV should take back the lead.

If you want to try this for yourself in a spreadsheet, here are the datapoints you need, with examples of the data:

EV’s battery capacity (kWh) – this is 100kWh for the Tesla Model S flagship
Household tariff (cents per kWh) – this can vary from 23.45 to 66.08 cents
Official EV range – 613km for Model S, 446km for Jaguar I-PACE
Petrol car’s combined-cycle fuel-economy figure – 3.4L/100km for Prius
Current petrol price – $150.50 according to Australian Institute of Petroleum
Cost of petrol per 100km travelled – multiply dollars/litre by combined-cycle figure
Calculated petrol cost to EV range – multiply cost petrol/100km by EV range and divide the product by 100

Only use numbers in the cells, so the spreadsheet program will treat those as numbers, not labels or text. Don’t include the units of measurement (km, kWh, litres, etc) with the numbers in the same cell.

Here are some battery-capacity and range numbers for EVs already in the market or soon to arrive:

Audi e-tron – 95kWh, 328km
Hyundai IONIQ – 28kWh, 200km
Hyundai Kona – 64kWh, 557km
Jaguar I-PACE – 90kWh, 470km
Mercedes-Benz EQC – 80kWh, 471km
Nissan LEAF – 40kWh, 270km
Tesla Model 3 – 75kWh*, 523km
Tesla Model S – 100kWh*, 613km
Tesla Model X – 100kWh*, 542km
* Lower capacity batteries also available

Extracted from Car Sales