What's all this about?

Audi's gone and done another hybrid, this time creating the A7 Sportback h-tron quattro for display at the LA Auto Show.

H-tron? I thought Audi hybrids were e-trons.

Ah, they are if they mate a normal internal combustion engine with their lithium-ion battery-powered electric drive. But this A7 doesn't. Instead, it uses another fledgling green car technology, the hydrogen fuel cell, as its main form of motive power.

What does this mean in terms of emissions?

The h-tron is exceptionally clean, emitting nothing more than water vapour from its tailpipes, which also means that the exhaust system can be made out of weight-saving plastic as it doesn't have to handle hot gases.

But I bet it has a pitiful range as a result, right?

Wrong. The A7 can do 31 miles on its electric drive alone, but power up the fuel cell and the h-tron will go 310 miles in zero-emissions comfort. It uses 1kg of hydrogen per 100km, which works out as about 76.4mpg in old money.

Crikey, that's not bad. Is it a lame performer?

Not really, although it won't get close to an Audi RS 7. With two electric motors on each axle (they nominally run at 85kW each but can be boosted to 114kW if the voltage is temporarily raised), it has quattro all-wheel drive. While peak power is less than the sum of its parts at 170kW (around 231hp), maximum torque is a colossal 540Nm, available instantaneously. So although the h-tron tops out at a modest 111mph, despite weighing 1,950kg, it can do 0-62mph in 7.9 seconds.

Does it look markedly different to a standard A7?

Nope, it's fairly conventional, aside from some badging. It's on show in Los Angeles right now and the word is that once the infrastructure and markets are ready, the A7 Sportback h-tron quattro will make production. We'll await that day eagerly.