Study finds PHEVs use 73 per cent more fuel than claimed

A New Zealand study has found that plug-in hybrid vehicle use, on average, 73 per cent more fuel than their advertised fuel consumption figure, but that PHEV technology is still the most frugal of any combustion-based powertrain.

The study was carried out by Consumer NZ and involved 12 different models – six hybrids and six PHEVs – from five popular auto brands: Toyota, Kia, Ford, Hyundai and MG.

Each vehicle was subject to a rush-hour commute, grocery run and weekend day trip to see how their real-world fuel consumption stacked up against their advertised figures.

“We record fuel use (both actual and on the trip computer) and measure electricity usage where appropriate, with PHEVs,” testers said.

“It’s an inexact science that doesn’t use any specialist or calibrated equipment, but it’s still a repeatable, real-world appraisal.”

When calculated at the bowser, Consumer NZ found the plug-in hybrid models consumed an average of 73 per cent more fuel than their claimed economy figure, whereas the hybrids used 20 per cent more fuel on average than claimed.

According to the vehicles’ trip computers, displayed fuel consumption figures averaged out to be 45 per cent higher than claimed for PHEVs and 10 per cent higher than claimed for hybrids.

Some of the best performers in terms of their percentage differences included the Toyota Highlander/Kluger Limited (2% indicated, 7% actual) and RAV4 Limited (17% indicated, 11% actual).

Meantime the worst offenders were the Kia Niro PHEV Earth (63% indicated) and Hyundai IONIQ PHEV (93% actual), the former of which used more than twice as much fuel as advertised (163% actual).

The best-performing PHEV was the Ford Escape ST-Line X, which consumed 13 per cent (indicated and actual) more fuel than its 1.6L/100km claimed figure.

Testers reiterated that while the tests were far from a “robust science”, they still provided a real-world reflection as to what consumers can expect from their electrified vehicles.

“It’s real-world driving with the percent gains blown out by the small numbers in the PHEV claims,” said Consumer NZ.

“Even so, it is quite telling in our sample that the figures were much higher than claimed.

“The key takeaway for consumers is this: If you’re in the market for a vehicle, only buy a PHEV if a lot of your driving covers shorter distances that will use the EV-only mode, and you are able to recharge the battery at home.

“If most of your trips are longer, you might be better off saving on the purchase costs and opting for a cheaper hybrid instead.”

The Motor Industry Association (MIA) – New Zeeland’s equivalent of Australia’s FCAI – has condemned Consumer NZ’s testing on the basis of the myriad variables involved in and affecting individual models’ consumption figures.

In an official response issued this week, the MIA criticised the not-for-profit organisation for overlooking the fact the PHEVs still used significantly less fuel than the hybrids and were still drastically more efficient than non-electrified combustion powertrains.

“The MIA also notes that car manufacturers don’t ‘claim’ that their cars will achieve the fuel economy stated in the test results. Manufacturers are required to undergo these strict regulated lab tests, and to publish the results, including here in NZ,” said the MIA.

“Manufacturer’s explicitly state that drivers will potentially experience different fuel economy than that stated on the fuel economy labels.”

“The purpose of laboratory testing is to compare the fuel economy of vehicles under identical driving conditions. A car consuming more fuel in the lab test compared to another model, can be expected to use more fuel than the other car in the real world too.

“But exactly how much fuel a car will use in the real world, will be different from that in the lab test. That’s because there are too many variables that affect how much fuel a car will use. These include driving style, traffic volumes, terrain, tyre pressure, vehicle condition, loads and even the weather.

“The bottom line is each person’s day-to-day driving is unlikely [to] match strict lab conditions. But in terms of fuel used, the Consumer NZ tests show that PHEVs are the most fuel-efficient type of vehicle people can buy if they want to reduce their fuel use.”

See below for tables outlining Consumer NZ’s findings.

Percentage difference from claimed fuel usage

* Source: Consumer NZ

Actual fuel and electricity costs per 100km

* Source: Consumer NZ

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