The BMW i3 range extender uses revolutionary materials, including the first ever application of Carbon Fibre Reinforced Plastic (CFRP), to create an electric car that is lighter than a 1 Series but has as much interior space as a 3 Series. It is ground breaking and you can read what we think about it here. In this summary we’re going to explain what the range extender option adds (or detracts) from the party.
The range extended market is in its infancy, and very different approaches are starting to emerge. Generally the concept is to provide a usable electric range but then have a back-up petrol or diesel engine which can be used to make electricity on board the car (there is no mechanical connection to the wheels), so there is no issue with ever being stuck at the side of the road if you run out of electricity, and opening up the possibility to buy an electric car even if you regularly exceed the daily electric range.
In the case of the i3, BMW has taken this concept to the extreme. Yes it has a petrol engine, but the fuel tank only holds 2 gallons (9 litres). This is because BMW doesn’t want you to drive the i3 on petrol all the time, rather it is an emergency back up that guarantees you won’t get stranded. The petrol engine in question is a tiny 650cc two-cylinder unit which, like the fuel tank, has been designed to squeeze into the platform without changing the size of the battery.
To reiterate the ‘occasional’ nature of the petrol back up, the tank only gives you an extra 70 – 100 miles of petrol range which you might notice means that if you drive an i3 in petrol mode you will not be getting 470 mpg but rather a very underwhelming 35 – 50 or so mpg which is approx 187 – 131 g/km CO2. The slight weight gain and the fact that the engine automatically starts when the battery depletes to 6.5% charge also means that the official electric range is reduced from 186 miles for the pure electric model to 146 miles. On the new WLTP test that equates to a 158 mile range for the pure electric i3 and 124 miles for the REX.
So the BMW i3 range extender is more expensive to buy, less efficient, slower, heavier, more expensive to run and has a petrol engine that you aren’t really supposed to use. However if you want an i3 but regularly travel just further than its electric range it allows you to buy one of the most innovative cars on the road today. It is more entertaining to drive than mainstream competitors, offers more interior space, and huge running cost savings and that is why we love it!
Estimated real world range: 90 – 140 miles (electric); 70 – 100 miles (petrol); 160 – 240 miles (combined)
BMW range estimate (Comfort mode, 20 degrees, urban): Electric – 112 miles; Petrol – 93 miles; Combined – 205 miles
Official range: Electric – 146 miles (NEDC); 124 miles (WLTP); Petrol – 93 miles
Official electricity consumption: 119 Wh/km* underestimated by test actually approx 140 Wh/km
Battery pack: 33 kWh lithium ion pack (27.2 kWh usable)
Recharge time: 240V charge 12 hours 15 mins; 7.4 kW fast charge 4 hours 50 mins; 11 kW 2 hours 45 mins; Rapid DC 50 kW charge 40 mins 0-80%
Please note that CO2 emissions quoted for electric cars are not directly comparable to diesel and petrol cars. This is because CO2 emissions quoted are calculated by Green Car Guide and include the emissions created at the power station turning fuel (e.g. gas etc) into electricity and in transmitting and distributing the electricity to an end user. They do not include the actual production of the fuel (e.g. gas extraction and refinery emissions). Petrol and diesel emissions are supplied by car manufacturers and are based solely on the fuel burnt in the engine (tailpipe emissions) and do not include the production of the fuel or distribution to a fuel station. In practice this means that electric car emissions are over estimated relative to petrol and diesel. For instance if an electric car, a petrol car, and a diesel car are all reported to emit 100 g/km CO2, the electric car actually has lower emissions.