Plug-in hybrid cars are 350% thirstier than claimed, European Commission says

It may not come as a big surprise, but your car is thirstier and more polluting than advertised.

When you buy your planet-friendly, plug-in hybrid vehicle (PHEV) from a smiling salesperson who tells you it should get two litres per 100km and will help prevent icebergs from melting, they are usually referring to the Worldwide Harmonised Light Vehicles Test Procedures (WLTP), a global standard introduced in 2018 with the aim of giving consumers a more realistic picture of a car’s fuel economy and CO₂ emission figures.

WLTP replaced the New European Driving Cycle (NEDC) used in Europe and other parts of the world, a laboratory-based test that was criticised for producing unrealistically low fuel consumption that wasn’t attainable on the road.

More realistic the new test might be, but diesel and petrol vehicles on the road are still about 20% higher in fuel consumption and emissions than indicated by the official WLTP values. This is based on recently released data collected by the European Commission from 600,000 cars since January 2021, when it became a rule for all new cars and small vans that run on liquid fuels to be fitted with fuel consumption monitoring devices to be sold in the EU.

The commission reports that petrol cars registered new in 2021 averaged 23.7% higher consumption and CO₂ emissions than the official type-approval average, while that of diesel cars were 18.1% higher.

The commission said the gaps were anticipated due to different factors affecting real-world emissions which can’t be fully replicated in the WLTP test such as the traffic and road conditions, landscape, ambient temperature, use of air-conditioning and on-board electronics, and driver behaviour.

However, for new PHEVs first registered in 2021, the real-world consumption and CO₂ emissions were on average 350% higher than the type-approval values, or about 4l/100km or 100g CO₂/km. It confirms these vehicles are not realising their potential, largely because they are not being charged and driven fully electrically as frequently as assumed, says the commission.

Unlike regular hybrids, which recuperate energy from their petrol or diesel engines while driving to keep the electric motor’s battery charged, PHEVs must be plugged in to recharge their batteries. PHEVs generally have larger battery packs than hybrid electric vehicles, which makes it possible to drive reasonable distances using just electricity (about 80km-100km in current models).

To address the PHEV consumption discrepancy, the commission has introduced changes to the calculation of the utility factor — the expected share of distance driven electrically — which is used to determine the CO₂ emissions during the official test procedure. These changes will be applied from 2025 and may be further adjusted based on real-world data.

It is not just about PHEV owners being apathetic about keeping vehicles charged though.

In our own road testing experience at Business Day Motor News, PHEVs have produced excellent economy when all was working properly, but keeping their batteries charged has sometimes proven challenging. The most recent models we evaluated were the Volvo XC90 T8 Recharge and BMW XM and both had technical issues that prevented them from being charged properly.

The Volvo would not charge at a regular household wall socket as it was supposed to, so we had to take it to a Volvo dealership and juice it up at their AC wall box. Thereafter, with the XC90 operating in hybrid mode it returned an astonishingly frugal consumption of just 1.2l/100km, even less than the 1.8l quoted by WLTP. The Swedish SUV has a range of 77km on pure electric power and, technical glitches aside, should be able to charge in a few hours at home.

The BMW XM plug-in hybrid also averaged 1.2l / 100km when driven in petrol-electric hydrid mode, and about 11l in full petrol mode when the battery was drained. It too had technical issues though; we took it to a BMW dealer where it juiced up to a range of 18km before the charging stopped for unexplained reasons.

PHEVs can be exceptionally light on fuel and justify being priced higher than regular petrol or diesel cars if you’re able to keep them charged.

The difference between claimed and real fuel-consumption figures has caused trouble for some car companies, including Ford SA, which in 2014 had to withdraw an internet advertisement that misled the public about the economy of its EcoSport. The ruling — one of several made by the former Advertising Standards Authority over the same issue — found that Ford’s advert didn’t sufficiently inform motorists that the quoted consumption figures were obtained in controlled lab conditions and thus weren’t realistically attainable by customers.

Since 2008, all car dealers in SA have had to display stickers on the windscreens of new vehicles, informing prospective buyers how fuel efficient the vehicle is and how much carbon dioxide it emits. However, some brands reflect WLTP data while others use real-world figures gleaned from local test drives conducted by the manufacturer. When buying a new car it’s worthwhile to ask the salesperson to which tests the fuel figures refer.