Plug-in electric vehicles are on the rise, with the Audi Q7 e-tron joining the A3 Sportback e-tron and R8 e-tron - taking the German maker's count up to three. There's clearly momentum behind electric, thanks to its efficiency, environmental and fuel-saving implications.

But going green might put you in the red. The Q7 e-tron's anticipated £65,000 starting price is a good £15k more than the combustion-only model - the one we took for a spin back in the summer of 2015 - which is a sizeable premium for this sizeable SUV. Is it worth it? We took the e-tron electric hybrid on the road to see what we made of it.

First thing's first, if you've thought about buying an SUV then the Q7 really ought to make your shortlist simply because it's a good looking driving machine that avoids being too tank-like in its ways.

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But - and it's a critical one - if your eyes have veered over to the e-tron version, hand on environmental heart, then you'll need to consider the space implication of the batteries. They've got to go somewhere, after all, and in the case of the Q7 e-tron that means it can only be a five seater, not a seven seater (which may sound at odds with its name, but that's that way it is).

But the obvious trade-off between seating arrangements is that the Q7 e-tron can scoot along happily using only its electric motor - which with 94kW of output, translates to 128bhp - for up to a 35-mile range per charge. That might sound quite conservative, but let's not forget this is a 2.5-tonne vehicle (it's 450kgs more than the standard Q7), so perhaps that's no surprise.

If you've got a commuting route with a charger at the other end (7.2kW charging means a refill in 2.5-hours; at-home means 8-hours per recharge), then you'll quickly save on those pricey diesel top-ups over the course of time.

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You can not only smugly breathe in the air with confidence when you park up too, thanks to 46g/km CO2 emissions (a significant improvement on the 148g/km starting of the combustion-only Q7), but there's no tax to pay as a result. Or C-charge if you're based in London.

Not that the Q7 e-tron is just electric, of course. With a 3-litre V6 turbodiesel engine under the hood, the combined 275kW/373bhp output gives this SUV plenty of grunt - and, driven hard, its actual emissions will obviously rise, but that doesn't affect the implications of purchase - to glide along roads at pace. It's a versatile driving machine.

Figures are figures though, and while important they're just numbers on the page. The real thing about the Q7 e-tron is just how comfortable it is to drive. In many respects, with added extras anyway, it's like a technological palace on wheels.

From a driver's point of view there's loads of space to push back into those comfy seats - here they're electrically adjustable, in a "cedar brown" leather with customised contour (£2,850) - and just relax. The 8-speed tiptronic auto box will look after you when it comes to driving, making everything rather effortless. Bumps? What bumps. It's a smooth drive.

It's also a near-silent drive when in the electric-only driving mode, which, given the high torque, delivers an immediate and rapid response when it comes to accelerating. Even on motorways the sound is more a light hum than intense roar, assuming you don't dump the throttle and cause the combustion engine to kick in and take over.

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Which brings us to the different driving modes available: Electric Drive (EV), which uses the electric motor only; Hybrid Auto, which utilises the battery in the electric motor, paired with the diesel engine for maximum output - boost delivers maximum output, coasting puts consumption to zero; Battery Hold, which uses regenerative braking to attempt to maintain battery levels while calling on the diesel engine when needed; and Battery Charge, which, as the name suggests, is all about recharging the battery through recuperation without the need for plugging in.

That might all sound rather complex, like "oh darn, which one do I pick?". But, in reality, the Q7 e-tron, just like the A3 Sportback e-tron, is intelligent enough to select the mode it needs - or thinks it needs - based on your driving.

Go too hard on the throttle, however, and you'll hugely impact on the fuel economy, which supposedly can be as good as 166mpg. Will you ever see that in the real world? Almost certainly not. We're a bit brisk in our driving style and weren't even hitting 50mpg (read that as 40mpg - which is better than out attempts in the combustion-only Q7, though), so go figure. Train your driving skills, however, and you can up the economy - it just takes practice.

There's one significant factor to help you do just this, called Predictive Efficiency Assistant (PEA). Because the Q7 e-tron maps the route ahead - if you're using the satnav - it knows the roads, the upcoming speed limits, and can predict the most efficient driving style. In the head-up display (which is part of the technology pack, £1,950) you'll see a green foot symbol, which is your cue to coast along until the symbol vanishes. And as that's in your eye-line, it's second nature to respond to it, safe in the knowledge you're saving yourself. Very clever.

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Whether in the front of the back, with some tech option boxes ticked the Q7 e-tron is a bastion of technology. Lots are pricey extras, however, as you can see from the various bracketed-out £-symboles throughout this article. But there are a few that we particularly love.

First up is the Audi Virtual Cockpit, which is a digital display beyond the steering wheel. It's standard in the latest Audi TT, but not so in the Q7 e-tron (it's £600). As the dials are digital they can be virtually repurposed for different displays - whether showing range in the centre screen section, speed, or some other metric, even the next turn on your satnav-guided route.

To control everything there's Audi's updated input system, which drops the touch-sensitive dial found in some of its other cars for a whole touch-sensitive pad, complete with eight shortcut keys up top. It's even got haptic feedback so you can supposedly feel a response to your input - although we couldn't feel anything, even after asking a technician to show us what the new pad was about, in the pre-release version. Sketching letters and numbers on this pad can be interpreted by the system, which is particularly useful for entering postcodes or names without taking your eyes off the road.

The main display is a centre screen risen beyond the dash, which in its 8.3-inch scale is ample without being overly distracting to the driving experience. It's a great spot to show up navigation, music, or phone sync information. There's even the option for Apple CarPlay or Android Auto if you want.

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Sit in the back and, in this configuration, there's a whole lot going on too. Audi Entertainment Mobile (£1,180) means two 10.1-inch touchscreens are fitted to the back of the front headrests for backseat passengers to be kept entertained. Although presumably you'll need to add the DVD changer (£600) to get the most out of them.

But perhaps the most expensive and most/least favourite of all the options is the Bang & Olufsen "3D advanced sound system". We love it because it sounds bloomin' amazing, but we hate that it costs an extra £6,300. That's a whole heap of cash, but from sub bass through to twinkling highs everything sounds amazing - and don't cut corners on the cheaper Bose upgrade, as it sounds surprisingly tinny (that's based on our experience in the latest Audi A4, anyway).

First Impressions

So it's big, it's comfortable, it's easy to drive and technologically sound. But is the Q7 e-tron worth it?

There's an increasing amount of competition. While the A3 Sportback was among the early models to push into the plug-in electric market, the ultra-popular SUV market has the likes of the Mercedes GLE500e, BMW X5 xDrive40e, Volvo XC90 T8 and even Porsche Cayenne S E-Hybrid in contention. The Audi certainly keeps its head above water against all of those, but it's not likely to be the cheapest, and without seven seats the more tank-like BMW will appeal more to some.

All said, however, and we still love that all 2.5-tonnes of this beast can be near-silently flung around almost any kind of road, enjoyed to the max both inside and out, and for the right driver save on fuel and tax in the long term.

Plug-in electric is still in its infancy, there's still a lot of progression to happen, but if you're adamant on buying one, and in particular an SUV, then the Q7 e-tron keeps up with the best of them.