THE name is as complex as the technology, however the BMW X5 xDrive40e is otherwise as simple to understand as it is to drive.

Its rear batteries funnel food forward to an electric motor mounted inside the eight-speed automatic transmission. On its own the motor contributes 83kW and 250Nm. The petrol engine, a familiar 180kW/350Nm 2.0-litre turbocharged four-cylinder from the 3 Series, also sends its contributions to the centre differential. It can then vary drive from zero to 100 per cent between front and rear axles, ensuring this plug-in X5 retains some off-road wares.

With a petrol-electric drivetrain, it is never a simple case of adding electric motor and internal combustion engine outputs. Combined power totals 230kW, matching the 3.0-litre turbo-diesel six-cylinder engine used in the X5 xDrive40d.

Total torque of 450Nm falls 180Nm short, however, bested even by the 500Nm X5 sDrive25d. Another inter-range comparison? The X5 xDrive40e has a claimed 6.8-second 0-100km/h that makes it no faster than the $17,000-cheaper X5 xDrive30d. It is also nine-tenths slower to that speed benchmark than its identically priced diesel ‘40’ sibling.

The surcharge pays dividends in terms of fuel consumption. Either recharged via a standard household powerpoint or a $1750-optional BMW i Wallbox fast charger, at five hours or half that time respectively, the batteries can turn their usable 6.8 kiloWatt hours into 31km of petrol-free motoring.

BMW stresses that this is a best-case scenario, and around 25km is more realistically achievable. However it also claims that the average Australian commute between home and work is 15.6km and 50 per cent of locals have a sub-10km drive on weekdays.

Choose a ‘green’ energy supplier and it will cost a maximum $2 to recharge, compared with around $1.20 for regular coal-fire powered electricity that BMW agrees defeats the environmental purpose of a PHEV – it merely shifts emissions from tailpipe to electricity plant smoke stack.

Comparatively, with diesel costing $1.05 per litre at the time of writing, an X5 xDrive30d with its identical performance will require $1.55 to drive 25 kilometres based on its claimed combined consumption of 5.9 litres per 100 kilometres.

In the same laboratory test designed to emulate mixed driving conditions, the X5 xDrive40e is rated at 3.3L/100km, however this figure includes its ‘free’ 25km electric head start. For successive bundles of 100 kilometres, if not recharged via a powerpoint, the PHEV can never re-achieve this figure. BMW admits a diesel would be more frugal over long distances.

To test its real-world capabilities, BMW sent us on a circa-100km drive around the outskirts of Canberra, the location for the national media launch of the X5 xDrive40e.

Jumping in and driving this X5 PHEV is no more difficult than its siblings. The same starter button brings the car to life, and the leather seats and dashboard trim are as sumptuous and accommodating as the X5 xDrive40d it shares specification with.

Up front, with its high-resolution 10.25-inch colour screen and brilliantly intuitive iDrive infotainment controller, this premium large SUV feels every bit as lush as expected for the $120,000 price. Heated front seats and four-zone, rather than dual-zone, climate control should arguably be standard, however – the only two glaring equipment omissions.

The rear quarters are similarly comfortable and spacious, with airvents mounted on the back of the centre console.

Incidentally, the X5 xDrive40e is the only model in the range where its air-conditioning can be set on and off with a timer to ensure cool entry on a hot summer’s day. It is because the air-conditioning works regardless of whether driver or passengers switch it on or off – it also automatically keeps the underfloor batteries cool.

There are three driver-selectable eDrive modes available.

Auto eDrive runs on battery power where available up to 70km/h, but fires the petrol engine if the driver increases throttle pressure. Max eDrive, as the name suggests, forgoes some power to retain electric mode at all times, if enough charge is available, up to 120km/h and unless the throttle is pinned.

Save mode pauses electric usage to then ‘save’ energy to be used later, such as around town, for example.

Curiously, there is essentially a hidden fourth mode, because sliding the transmission lever to Sport mode means the petrol engine will recharge the batteries.

We started in Auto eDrive where the whirring silence was occasionally broken by the contributing petrol engine. At an average speed of 48km/h we managed to travel 29km mainly on battery power, but with consumption of 2.7L/100km – already almost exceeding the combined cycle claim.

Having left Canberra’s urban centre, we switched to Sport mode through some twisting country touring roads. Average speed increased to 54km/h and we steered another 45km in around one hour. In that time the X5 had recharged its batteries to 80 per cent but consumption soared to 9.6L/100km.

For the third leg, we re-used that 80 per cent charge to pin the X5 in Max eDrive mode, travelling 17km on electric power alone over 33 minutes at 35km/h average speed, all with absolutely no petrol interference. Gently cruise and this heavy BMW will be happy to comply with your eco needs.

For the fourth leg, we went back to Auto eDrive but this time without any charge remaining and without using Sport mode. A further 17km back to Canberra airport resulted in consumption of 4.9L/100km – partially offsetting the near-double figure that helped recharge the batteries earlier.

It’s an impressive real-world figure for a large car, but consider it took only 34km to exceed the 3.3L/100km combined claim by 50 per cent and it becomes slightly less fortuitous.

The X5 xDrive40e also feels heavy and occasionally unwieldy to drive. As with all current X5 model grades, the steering is awfully vacant on the centre position. The adaptive suspension pitches noticeably in its standard Comfort mode, yet becomes more fidgety in Sport mode than expected considering the sensible 50-aspect 19-inch – albeit run-flat – rubber. It’s decent, but not great, in this regard.

Although the economy benefits are often exceptional, when the throttle is extended, performance and refinement are not up to the standards of its exceptional diesel counterparts. For a $120,000 vehicle there is a touch too much four-cylinder petrol growl too often.

The X5 xDrive40e would be a better vehicle combining an electric motor with a diesel engine, but primary markets such as the US and Japan have appetite only for petrol-engined hybrids.

Its concept is sound and execution impressive, until you consider the allure of the syrupy smooth diesel versions of the X5 available for around the same money as the PHEV. Without any incentives to buy ultra-frugal vehicles in this country, this is not a fault of its maker and BMW Australia has done well with pricing given the vehicle complexity.

It’s best to place politics aside, though. This BMW is luxurious to sit in and intelligent with its technology, but being only competent to drive for the price means it is not the ‘Ultimate Driving Machine’ take on a plug-in hybrid electric vehicle that some buyers of the brand may expect.