Electricity is a reluctant fuel in cold weather. Compared with summertime running, range drops by 25 per cent at minus 5, power delivery's stifled when batteries are cold, and interior heaters rob up to 60 per cent of charge. So it seemed like a good idea to see if our 2012 Green Car of the Year, the Vauxhall Ampera, was still the most viable EV option out by testing its sub-zero credentials.
Which is why we're currently in Estonia, a country enjoying uncharacteristically balmy winter temperatures of minus 14 degrees Celsius. And seeing as water and electricity make such a stimulating combination, we thought we'd take in some Baltic ice roads, which amount to six floating motorways between 4 and 10km long, allowing residents of the islands that pockmark Estonia's coast to travel to the mainland more quickly than ferries allow.
It's also an auspicious time to bring the Ampera here. Estonia has the world's first nationwide charging infrastructure, comprising 163 charging stations dotted every 50km. It's also got the highest European incentives - as much as £10,400 for the Vauxhall. And it's a market GM's keen to crack. It's already cornered 21.2 per cent of European market share with more than 5,293 of the 24,912 passenger EVs on the road wearing an Opel or Vauxhall badge.
Which, in some way at least, explains why we're currently drag-racing a ferry. It's tinkling through the ice about 20 metres to our left, just past a pair of navigational buoys, frozen at 45 degrees. And why the sat-nav display is, quite rightly, showing that we're in the middle of the ocean.
The Baltic Sea has a lot less salt in it than most, you see - around seven parts per thousand compared with an average of 35 parts per thousand. That's largely due to freshwater run-off from the surrounding lumps of Scandinavia and Eastern Europe - combined with its relative shallowness (and some other complex marine science), it only needs to be at freezing point to cultivate an icy lid.
So, what are the consequences of falling in? Assuming you took a ten-second dunk followed by a ten-minute walk to safety in -14 degrees centigrade (the temperature during our stay), you would initially start to shiver, then get a bit confused. After which you'd stop being able to use your hands, then turn blue, followed by a huge decrease in pulse and respiration rates, organ failure and a severe disinclination to boogie.
Which is why thumping over a ramp that bridges a noticeable crack in the ice is a little bit terrifying. Two blokes to the right nervously measuring the surface's depth, then a man in a skidoo draws up alongside us, points his index finger to his temple and starts making circular motions. We may have been going a little bit too fast. Or too slow...
Ice roads have their own esoteric speed limits. You can chose between two parameters: 15-30km/h and 45-70km/h. The differing margins are all about resonance - rumbling two tons of car across 22cm (roughly two iPhones) of ice causes quite a lot of vibrations, and between 30km/h and 45km/h you're transmitting damaging energy and not moving quickly enough to spread it across an area large enough to soak it up without the sinky sort of consequences.
Read the full article about their experience and test results here
* Photo made by TopGear: www.topgear.com/uk/photos