PHEVs fail Consumer fuel efficiency test

‘Real life’ driving of hybrid and plug-in hybrid electric vehicles (PHEVs) runs up larger-than-expected fuel bills, a Consumer NZ trial reports.

The trial found that when measured at the pump PHEVs used on average 73% more fuel than the manufacturers’ claims, while hybrids averaged 20% more fuel use.

The watchdog was commissioned by Te Manatu Waka Ministry of Transport to assess the fuel use of five brands’ PHEVs and hybrids to see how normal use compared with manufacturers’ claims.

“Some PHEV manufacturers claim their vehicles require very low fuel use,” says Consumer NZ test content team leader James le Page.

Manufacturers’ fuel efficiency figures come from lab tests held under controlled settings.

“However, when you drive a vehicle on ‘real roads’ the efficiency is likely to be lower,” says le Page.

“The fuel usage was much higher than manufacturers claimed.”

The difference in fuel efficiency was also evident in each car’s computer, which showed that PHEVs used on average 45% more fuel, and hybrids used on average 10% more than manufacturers’ claims, says Consumer NZ.

Each vehicle in Consumer’s trial was driven on the exact same routes, including a rush hour commute to and from Consumer HQ in Whitmore Street, Wellington, a supermarket trip, and a weekend run over the Remutaka Hill near Wellington.

Each vehicle drove 270km over the course of a week, Consumer NZ adds.

It explains that fuel use was recorded at the petrol pump – by calculating how much fuel was used on the trips – and on each car’s computer.

“Our trial didn’t use any specialist or calibrated equipment,” le Page explains.

“Instead, we opted for a repeatable, real-world approach, where each vehicle received the same treatment and test.”

Consumer’s findings echo those of European clean transport campaign group Transport and Environment. In 2020 it found emissions and fuel use were, on average, more than two and a half times those of official test values.

“Our trial is the first of its kind in New Zealand and highlighted a staggering difference in the fuel efficiency between different models of PHEVs and hybrids,” says le Page.

“It’s worth doing some research before splurging on a new vehicle,” he says, adding that people in the market for a new vehicle should consider becoming a Consumer member.

“We have just published the results of our expert tests on over 70 EV, hybrid and PHEV models assessing their performance, comfort, city vs highway driving and more.”

Motor Industry Association chief executive David Crawford says MIA seeks to “bring some balance to the discussion”.

“Overlooked in those test results was that the actual fuel economy achieved was still very low – ranging from 1.4 litres per 100km to 3.1 litres per 100km, depending on model.

“These are still very low fuel consumption figures, lower than a hybrid and impossible to achieve in a conventional-engined vehicle,” the MIA explains.

“Even though Consumer NZ did not test conventional-engined vehicles, the reality is they would have also used more fuel than the official figures under the same conditions.”

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.”

MIA says 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 (among) the most fuel-efficient type of vehicle people can buy if they want to reduce their fuel use.”