Plug-in hybrids are selling well, particularly in large European markets where generous government incentives slash the cars' high starting prices.
Consumers like them because it's possible to drive electric, as long as the battery is charged, without range anxiety because the combustion engine and a full tank of fuel are there as a backup.
Automakers love them because plug-in hybrids help the companies reach their CO2 targets, avoiding big fines from EU regulators.
Opponents of plug-in hybrids include environmental groups, which call them "fake electrics," arguing that real-world driving of the cars result in much higher fuel consumption and CO2 emissions than promised from WLTP tests. Therefore, green groups says plug-in hybrids do not deserve to receive the big subsidies from governments.
Determining how much fuel is saved and how much CO2 is reduced compared with a fuel-powered car is tricky. The share of kilometers driven in full-electric mode depend on factors such as the utilization pattern of each driver, the availability of recharge points and how diligent the owner is about keeping the batteries full.
I'm the relatively new owner of a Seat Leon plug-in hybrid. I used the first 2,000 kilometers to answer questions such as: How much fuel and electricity did I really consume? How different were my results from what was promised by the WLTP figures?
Let's take out the calculator
The Leon's on-board computer shows the car's average fuel and kilowatt hour consumption figures at any time. At my chosen cutoff point for this exercise of 2,103 km driven, my average electric energy consumption was 6 kWh per 100 kilometers, said another way, that is 16.6 km per kWh. I used 83.51 liters of gasoline, resulting in consumption of 3.97 liters per 100 km. That means I traveled a little more than 25 km per liter. The car's figures were confirmed by my own calculations, based on how many liters I put in the tank.
These figures, however, do not reveal how efficient the car was during electric-only or gasoline-only driving. To verify those figures, I ran two short separate tests.
With a 12.8-kWh battery charged at 100 percent, the cockpit computer gives a 62 km range, or 4.84 km/kWh. I started with a battery charge of 86 percent (11 kWh). Before it got to zero I managed to go 47 km, mixing both city and highway driving. That is equal to 4.3 km/kWh , which was done under ideal weather conditions of 20 Celsius so I needed no air conditioning. That tells me the promised WLTP range of 60-plus km is quite attainable in city driving.
How about driving only using the gasoline engine? To do this I set the computer parameters to "no recharge" and traveled 153 km with zero battery. My test route was a third city driving and two-thirds motorway (at speeds of 90 to 120 kph). The result was fuel consumption of 5.5 liters per 100 km (18.2 km/liter).
I then cross-checked things a different way. At the rate of 4.3 km per each kWh calculated above, with the 167.26 kWh I put into the battery, the car has run approximately 720 km in electric-only mode. Subtracting that from the total driven, 2,103 km, results in 1,383 km traveled using 83.51 liters gasoline, or 16.6 km/liter. The latter figure was not as good as my test above (18.2 km/liter), most likely because of my higher average speed while driving on the highway.
The 16.6 km/liter figure is also very similar to what I used to average with my previous car, a 1.0-liter, three-cylinder gasoline seventh-generation Golf with a dual-clutch transmission.
That did not surprise me because my Leon's ability to recuperate energy while braking is offset by two factors: it weighs more than my old Golf and its more powerful 1.4-liter, four-cylinder gasoline engine uses more fuel.
The unsustainable optimism of WLTP
How does my overall fuel consumption of less than 4 liters per 100 kilometers rate? It's better than what any compact hatchback with an internal combustion engine could achieve in the real world. However, it is still nowhere near the 1.1 to 1.3 liters per the first 100 km promised by the WLTP results for the Leon.
The main reason for the gap is the proportion of distance the vehicle travels electrically, which is called utility factor (UF) by the WLTP test procedure.
The WLTP test for plug-in hybrids assumes a higher UF as the electric-only range of the vehicle grows. Therefore, the Leon's 60-plus km of range results in a UF of close to 0.8, which means fuel consumption and emissions are computed on the base of 80 percent of the kilometers driven in full-electric mode.
As my results show, only a third of my kilometers were driven in full-electric mode, so my UF was 0.33.That alone explains the difference between my real world result of 4 liters per 100 km and the 1.1 to 1.3 liters per the first 100 km from the WLTP test.
The same is true for CO2 emissions, which are directly linked to fuel consumption. The Leon's CO2 figure based on WLTP testing is 25 to 30 g/km. At an average of 4 liter of fuel per 100 km CO2 output is 94.5 g/km. This result confirms the following claim by the International Council on Clean Transportation: "Plug-in hybrid fuel consumption and tailpipe CO2 emissions in real-world driving, on average, are approximately two to four times higher than type-approval values."
Conclusions
How efficient a plug-in hybrid is mostly depends on how often the battery is recharged, which is not easy in a big city, especially if you do not own a garage or parking space.
Driving a plug-in hybrid, however, is surely good for CO2 emissions even if just a third of your driving is electric only, as was the case with me. Moreover, I deliberately drove nearly 100 percent of my city routes with zero emissions to help reduce pollution downtown.
That being said, determining whether a full life-cycle assessment would shows a positive CO2 balance for a plug-in hybrid goes far beyond the scope of this story.
Do plug-in hybrids deserve to be treated as electric cars? Probably not.
One last question, though, can receive at least a partial answer. Did I spend less or more by driving electric? The 16.6 km per liter are approximately four times what you can drive with one kWh. Gasoline in Italy currently costs 1.59 euros a liter. On a pure cost-of-fuel comparison, then, parity will come with electricity costing about 40 cents/kWh.
If you recharge at home you can spend as little as 20 cents/kWh, while the cost of public stations in Milan varies from 37 to 45 cents/kWh. Again, it all depends on where and when you can replenish your battery.
