When you hear that a car is 'Twin Engine', it's enough to set the imagination alight. What's this, a 150 mph supercar with a couple of engines strapped together for double the performance? Some exotic new racing car with conjoined machinery and acceleration like a rocket?

The reality is a bit different. What we have here is a new variant of the multi-award winning car that is currently rated as the safest model ever assessed under the Euro NCAP crash test programme. Volvo's XC90 has acquired a plug-in hybrid version.

 XC90 T8 Twin Engine

It's called the XC90 T8 Twin Engine, and the latter bit of its name alludes to a two-litre petrol engine which is both turbocharged and supercharged, working in harness with a lusty electric motor. Linked with these two power sources is a big 16-cell lithium-ion battery pack that is plug-in rechargeable.

Multiple twins

This is not Volvo's first hybrid model. It already has a V60 Plug-In with a diesel-electric combination. But the XC90 T8 is the first of what the Chinese-owned Swedish car maker describes as “a lot more T8 Twin Engine cars from Volvo.” It is also the first seven-seater plug-in hybrid car on the market, and is expected to remain the only one for the foreseeable future.

 XC90 T8 Twin Engine

It's a powerful big beastie too, with 320 bhp from the petrol engine and an 87 bhp electric motor, which deliver a combined total of 376 bhp – no, my maths haven't gone astray; the drivetrain absorbs some of the energy jointly produced by the two engines. Even so, it has plenty of punch.

With an eight-speed auto transmission and all-wheel-drive, the XC90 T8 is no slouch. Its top speed is quoted at 140 mph, and 0-62 acceleration is in a sportscar-like 5.3 seconds. The quoted combined fuel economy figure is a hugely impressive 134.5 mpg. Realistically, though, it delivers economy around the 75 mpg mark, as shown by the dashboard read-out after a lengthy town-and-country test drive.

Choose your mode

 XC90 T8 Twin Engine Interior

When you switch on, the car's default setting is hybrid mode, drawing on both power sources and varying their use depending on the conditions and the way you drive. Dashboard aids let you know when you're drawing on stored battery power, and also when energy recouped from braking – or the engine braking effect of backing off the throttle going downhill – is being fed back to the battery pack.

By selecting Eco mode, the car can be driven for up to 27 miles on battery power alone. It doesn't sound much, but it is enough for a commute from the suburbs into a city centre using stored electricity alone, with the petrol engine on shut-down and no emissions from the tail-pipe.

 XC90 T8 Twin Engine dash

Using a charging cable that comes as part of the car's kit, you can plug it into an electricity source to top up the battery pack. This can be via a normal household 13-amp socket, but that takes many hours. The time is drastically reduced if an electric car charge point is used. Having one installed at home costs £190, although the price will go up to £395 from March.

Smooth operator

 XC90 T8 Twin Engine badge

Apart from discreet badging, there is nothing much on the outside to tell you that this XC90 is any different from the standard diesel model. Unless, that is, you spot the T8's extra filler flap located on the nearside front wing, where the charging cable plugs in. Inside the cabin, there is a clue in the chic crystal gear lever, which other XC90s don't have.

The hybrid XC90 is a smooth operator, with powerful performance, lively acceleration and excellent refinement. When running on battery power it is whisperingly hushed, but even when the petrol engine is in operation it is still quiet and civilised. Unlike many other hybrids, boot space is unaffected by adding all the hybrid kit. It helps that it's a big car to start with.

 XC90 T8 Twin Engine rear

Pricing for the XC90 range starts from £46,250. The T8 Twin Engine, though, starts from £60,445, but it is eligible for a £2,500 government grant that drops the bill to just under £58,000.

All images: Sue Baker