ROME – There is an important hole in the information provided to consumers by the homologation data relating to the consumption of plug-in hybrid cars. A plug-in hybrid car with a declared consumption of 1.5 liters / 100 kilometers on the homologation cycle actually recorded a significantly higher energy consumption during the test than just one and a half liters of petrol or diesel. And nobody takes it into account. The declared consumption, in fact, concerns only the fuel and does not consider at all the electricity consumed by discharging the batteries while going through the test cycle.
The communicated value is therefore only partial with respect to the real energy consumption on board. Consequently, even the economic cost per kilometer that the customer calculates on the basis of this data to make his choice is nothing short of misleading. Engineer Fernando Ortenzi, Enea car testing expert, is very clear about this: “The homologation test of plug-in hybrid cars is carried out starting with a fully charged electric storage battery and using all the charge during the test – explains. But that’s not enough, because the fuel consumption indicated as a result of the test is further corrected based on the range in electric mode that the model is able to guarantee. All this electricity is not in the final consumption reported by the manufacturers “.
The plug-in hybrid car during the homologation test, therefore, mainly consumes the electricity accumulated in the battery, then when the electric energy is no longer able to allow driving, it favors the petrol or diesel engine and starts consume more fuel. And even the fuel consumption, recorded after the batteries are exhausted, is further corrected downwards. This is because it is assumed that in real use the motorist will carry out further recharges, considered proportional to the model’s ability to guarantee autonomy in electric mode only.
If a motorist, when evaluating the choice of a plug-in hybrid car, calculates only the economic expense related to the fuel declared in the homologation consumption, he is making a big mistake. That petrol or diesel consumption, usually indicated by referring to 100 kilometers of travel, alone is not capable of making the car travel that distance under test conditions. The actual value to be considered for the calculation of the expense must also take into account the cost of electricity for a full recharge and beyond.
“This has nothing to do with the difference between homologation consumption and real consumption – specifies Eng. Ortenzi of Enea – but it concerns precisely the homologation data which, in order to be homogeneous with those provided for other technologies, should also indicate the consumption of the electricity with which the battery was charged before the start of the test and which is supposed to be used later, based on the calculation linked to the zero-emission driving range “. The data communicated to the customer regarding the homologation consumption of a plug-in hybrid car is therefore true if we consider only the fuel used by drawing from the tank, but absolutely partial if it refers to the electric operation of the car.
The problem of energy costs goes beyond the question of the plug-in hybrid car and is all in the inability of current market rules to communicate the consumption of different forms of energy in the univocal way. We speak of liters if we refer to fuels, of kilowatt hours if we refer to electricity, of cubic meters or kilos when we are dealing with gas. Yet energy has a very precise unit of measurement in the international system and it is the Joule, which no one names except in the technical field but which is proportional to the kilowatt hour, the most correct of the commercial units of measurement.
If in the homologation consumption of a plug-in hybrid car reference was made to kWh there would be no doubt, the electricity of the battery should certainly be considered. Otherwise the published data would obviously be incorrect and not simply partial.