PHEV Economy Calculator

A plug-in hybrid nobody plugs in is a heavy hybrid hauling a battery it never uses.

Real consumption3.012 L/100 kmat 53.7% of miles on electricity

Official utility factor53.7%for 50 km of electric range, assuming you always charge

Official consumption3.012 L/100 km

Annual fuel452 Lover 15,000 km

If you never charged it6.5 L/100 kma heavy hybrid hauling an unused battery

Extra fuel from never charging523 L a year

Utility factor at double the range78.5%diminishing returns — the distribution of daily distances has a long thin tail

Fleet data has found real utility factors well under half the official assumption for company cars, because the fuel card pays for petrol and the driver pays for electricity. A plug-in hybrid nobody plugs in is a heavy hybrid carrying a battery it never uses.

The formula

blended consumption = petrol consumption * (1 - utility factor)

The utility factor is everything

A plug-in hybrid's official consumption assumes a particular share of miles driven on electricity, and that share is fitted to the distribution of daily driving distances rather than measured on your car. Short trips run entirely on the battery; long ones run mostly on petrol. The official figure describes an average driver, and almost nobody is one.

A PHEV nobody plugs in is a heavy hybrid

This is the genuine finding from fleet data, and it is not marginal: real utility factors for company-car PHEVs have come in at well under half the official assumption, because the fuel card pays for petrol and the driver pays for electricity. The car is carrying a battery it never uses and an engine hauling that battery around.

Range matters with diminishing returns

Going from 20 to 40 km of electric range captures a large share of additional trips; going from 60 to 80 captures far fewer, because the distribution of daily distances has a long thin tail. That is why PHEV ranges cluster where they do rather than growing indefinitely.

How much to trust a footprint

Life-cycle figures for the same product routinely differ by a factor of two between studies, because deciding what to count — the farm, the packaging, the shop, the drive home, the disposal — is a methodological choice rather than a measurement. The numbers here are central estimates from published meta-analyses. They are reliable for comparing one option against another, which is what people actually use them for, and not reliable to the second significant figure.

The other thing worth keeping in view is scale. Individual choices matter and they are not where the emissions are: the difference between the best and worst quartile of beef producers is larger than most people's entire dietary footprint, and that is a question about agriculture policy rather than about shopping.