On the face of it, coupling a small petrol engine to a high-powered battery should be a match made in PHEV-en.
You see, PHEV (or Plug-in Hybrid Electric Vehicles as they are known) have been around for some time, with the likes of the Toyota Prius and all-electric Nissan Leaf leading the way on the Electric Avenue.
However, not to be outdone by the Japanese, German brand BMW took things to a whole new level when it produced its i8 supercar, that featured just a 1.5-litre petrol engine from its MINI sibling and a 96kw electric motor.
The results were phenomenal. With claimed economy figures from as low as 2.1l/100km, a top speed of 250kph and 0-100kph sprint time of just 4.4 seconds, the i8 certainly had the best of both worlds.
Following on from that, BMW then introduced two new models to its iPerformance range in the shape of the 3-Series 330e and X5 xDrive 4.0e plug-in hybrids.
The X5 xDrive 4.0e combines a two-litre four-cylinder turbocharged petrol engine with an electric motor that drives all four wheels through an eight-speed gearbox.
BMW claim that between the two you get a total output of 313bhp and the ability to reach 100kmh in 6.8 seconds.
Even better news for potential buyers is that the annual road tax costs just €170 a year, compared to a 40d that will set you back a whopping €570.
However, these new plug-in hybrids have pros and cons.
Having recently reviewed the new 330e on these pages against the 320i, we came to the conclusion that the 330e didn’t exactly live up to its expectations.
Similar to the 330e, the X5 xDrive4.0e plug-in hybrid comes with a slightly more powerful 2.0-litre petrol engine matched with the exact same lithium-ion battery.
According to BMW, you can travel up to 35km in pure electric mode and can go at speeds of up to 120kph before the petrol engine starts to kick in.
Again, for someone like me who has a 28km return journey to the office each day, I should be able to get in and out of town on one full charge without having to use a drop of juice.
Unfortunately, as with the 330e, the figures didn’t seem to add up, and I couldn’t get in and back without the use of the petrol engine.
On top of that, because the 4.0e is fitted with a sizeable battery in the rear, the folding third-row seats are now no longer an option.
The boot, too, is slightly smaller than its diesel siblings.
But then again, there is a serious saving on costs.
On the road, I found the X5 xDrive 4.0e plug-in hybrid a dream to drive.
BMW claim that, even with the battery pack in the back, the weight distribution makes it as good to drive as a standard one – but I didn’t find this the case.
I would definitely have a 3.0-litre diesel over it any day.
What it really comes down to is how you make use of this amazing technology.
I am lucky enough to have an electric wallbox outside my home, where I can make proper use of the electric cars I test.
But trust me, if you don’t make use of the battery power you are wasting your time.
A couple of times when I didn’t charge this X5 up and drove around on the normal petrol engine, I found it extremely thirsty. So much so, that it was averaging more than 10 litres per 100km – that’s not exactly green.
Overall, it comes down to personal choice. I’m going to stick my neck on the line and say that, even with government savings, I’d still choose the X5 xDrive 3.0d I drove last year.
Prices start at €73,670 ex-works for SE and €80,450 for M-Sport versions.
A €2,500 VRT rebate cuts the price to €71,170. The diesel xDrive25d SE, by comparison, starts at €72,760.
Sadly, its emissions are just two grammes above the 75g/km mark that would have knocked €5,000 more off in the form of an SEAI grant.
Model: BMW x5 40e M-sport
Price: From €71,550 (test car €87,000)
Road Tax: €170
Max Speed: 210kph
Fuel Economy: 3.3l/100kms combined (claimed)
Boot Space: 500-litres