It’s a challenging time for diesel owners, assaulted regularly as we are in the media, and by the medical experts, for the noxious gases that our engines emit, and threatened with exclusion from city centres, or with heavy charges whenever we might need to enter them. So there is undeniable pressure to consider alternative power forms to diesel for “eco” drivers, and these are worthy of some closer examination, particularly by relatively high annual mileage business drivers, for whom diesel power has always been the “best buy”. Is this still the case?

We’ll look at diesel, or electricity, costs for a driver whose daily commute is 25 miles each way, and who covers an average of 100 miles every weekend, with annual holidays, in a typical mid-range business diesel, in this case the Skoda Octavia SE L 2.0 TDI. The mileage then conveniently comes out to near enough 18,000 miles a year and, with 55 to 65mpg economy and diesel at £1.32/litre/£6.00/gallon) the Octavia requires an annual spend of £1,600 to £2,000, or 9 to 11p per mile.  

Now let’s imagine that this owner is driven by the anti-diesel pressure and stock availability to switch to the nearest petrol alternative, an Octavia SE L 1.5 TSI. The expected fuel economy will now be 40 to 50mpg and, with petrol at £5.50/gallon, annual fuel costs on the same basis becomes £2,000 to £2,400, or 11 to 13p a mile, meaning an extra £400 a year over the diesel Octavia. We’ve calculated both sets of costs for the manual variant, and expect a similar picture for DSG transmission, or possibly slightly higher costs for both as automatics. 

Now let’s look at a fairly equivalent hybrid car which, almost by default, has to be a Toyota Prius Business Edition Plus. It can undoubtedly deliver some 60 to 65mpg, although long, fast, trips would drag this down to 45 to 50mpg, and thus we have a wider spread of annual fuel costs, of £1,600 to £2,000 a year – 9 to 11p/mile, and is much the same as the Octavia 2.0 TDI, with higher costs for motorway driving.

Finally, we need to identify an equivalent plug-in electric hatchback, and are struggling, with a sub-£30,000 budget, to find anything more obvious than the fine Hyundai Ioniq Premium SE. With a realistic 4 miles per kWh, we’re giving it a range, with its 28kWh battery, of around 100 to 120 miles, which should give our owner no range concerns, other than perhaps on annual holidays or long weekend runs. Based on overnight home charging of the traction battery, costs for the 10kW of juice used on its daily commute range from £1.00 to £1.50, dependent on whether or not an Economy 7 low cost night tariff is available from the electricity company. Annual fuel costs, boosted by a nominal figure of £200 for on-road charging during some longer trips, then amount to some £560 to £740, or 3p to 4p per mile. 

With the diesel, petrol, and hybrids, we see a spread from 9p to 13p a mile for fuel costs, against which the Ioniq’s 3p to 4p a mile means significant savings of around £1,500 a year. So the argument for the Ioniq hardly needs questioning on fuel costs, but what about depreciation? The Prius has a fine record for residual values, which the Ioniq will possibly match, in time, but reliable projections are hard to find. With modest discounts on the Hyundai, and its true residual values unknown, and similarly modest discounts on any new Prius, the fossil fuel cars move back into contention. You can find very good cash discounts on new Octavias, which hold their value fairly well and, petrol or diesel, are significantly cheaper to buy than our hybrid and all-electric comparison cars. 

So the likely savings of £2,500 to £3,000 in fuel costs over two years and 36,000 miles come into perspective, particularly when paying £6,000 to £8,000 more to buy the new Ioniq, with cash or with finance. Make of this what you may, and you can apply our calculations for other annual mileages. (We have omitted costs for plug-in hybrids, which are too variable to allow reliable calculations.) But we must bear in mind two things: firstly on-road EV charging can be quite costly, and often inconvenient, if you’re out on business, and secondly, these comparisons only stand up whilst EV charging electricity remains cheap, and virtually untaxed, aside from the five per cent VAT!

Victor Harman