A Consumer NZ trial has found ‘real life' driving of hybrid and plug-in hybrid electric vehicles (PHEVs) runs up larger-than-expected fuel bills.

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

The watchdog was commissioned by Te Manatū Waka, the 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 James le Page, Consumer NZ test content team leader.

Manufacturers' fuel efficiency figures come from lab tests conducted under controlled settings.

'However, when you drive a vehicle on ‘real roads' the efficiency is likely to be lower.

'The fuel usage was much higher than manufacturers claimed,” says le Page.

The difference in fuel efficiency was also evident in each car's computer, which showed that PHEVs used on average 45 per cent more fuel, and hybrids used on average 10 per cent more than manufacturers' claims.

The trial

Each vehicle in Consumer's trial was driven on the exact same routes, including a rush hour commute to and from Consumer HQ, a supermarket trip, and a weekend run over the Remutaka Hill. Each vehicle drove 270km over the course of a week.

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

The findings

Consumer's findings echo those of Europe's leading clean transport campaign group, Transport & Environment. In 2020 it found emissions and fuel use were, on average, over 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.

'It's worth doing some research before splurging on a new vehicle.

'If you're in the market for a new vehicle, 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.”