FROM driverless cars to electric vehicles charged by household "solar roofs", the way we drive is about to undergo its biggest revolution since the Model T first rolled off the Ford production line in 1908.

Tomorrow will see the much-hyped unveiling of a new product by electric car super-brand, Tesla, in California.

There has been fevered speculation online about what the mysterious new venture might be ever since billionaire CEO, Elon Musk, tweeted a teaser - saying the new product will be "unexpected by most" - last Sunday.

Musk added that the unveiling would be followed up with a joint event between Tesla and green energy company SolarCity on October 28, leading some to suspect that tomorrow's launch will be linked to a new solar panel innovation. Tesla is on the brink of a merger with the US solar panel firm and Musk has already confirmed that the press conference will mark the official launch of the Tesla/SolarCity solar roof, which they envisage could see up to five million homes in the US replace their entire rooftops with electricity-generating solar cells.

Once installed, these solar roofs would be integrated with Tesla's latest lithium-ion home battery, the "Powerwall 2.0", and the Tesla home charger. In essence, it means that the car owner becomes entirely self-sufficient - as one commentator put it, "electricity generation to energy storage to energy consumption in a single package".

Others have simply called it a "game-changer".

It might not be transforming rooftops in Scotland next week, but if the technology takes off in the US it will not be long before it crosses the Pond.

Tesla opened its first Scottish showroom in Edinburgh in December last year and the popularity of alternative-fuel vehicles (AFVs) is soaring in the UK. Sales of new pure-electric vehicles are up nearly 17 per cent so far this year, compared to the same nine-month period in 2015. In September, nine in every 2000 new cars sold was a 100 per cent electric plug-in and more than one in every 100 new registrations in the UK is now an AFV, which includes petrol- and diesel-electric hybrids.

Professor Tariq Muneer, professor of energy engineering at Edinburgh Napier University's Transport Research Institute, said electric cars will not only become the norm - they will also make roads safer by motivating drivers to save energy.

He said: "If you drive at 30mph in an electric car then drop the speed to 20mph, you save 40 per cent electricity. People in petrol cars take the fuel for granted, but from a safety point of view electric cars are very good because it makes the driver conscious of how they can extend mileage at low speeds. If you get 40 per cent more mileage at 20mph than 30mph, then you're going to drive more carefully.

"Noise-wise, pollution-wise, safety-wise and climate change-wise, electric cars are the way we're going. Personally, I think the days of fossil fuel cars are numbered. I don't think we'll see many after about 15-20 years."

For most motorists, a combination of "range anxiety" - the fear of running out of electricity mid-journey - and the initial upfront cost of an electric car together with its steep depreciation are the main drawbacks of going green. A Nissan Leaf, one of the most affordable pure electric cars on the market, retails from around £26,000, but buyers are entitled to government grants of up to £5000 and charging points can be installed for free in their driveway.

Muneer insists that, in reality, the economics of electric and petrol vehicles are "about neck-and-neck".

"The running cost of an electric vehicle is no more than three pence per mile, so the main cost is the depreciation - but that will change as the market grows," said Muneer. "Maintenance costs for an electric car are very low because there's hardly anything to be serviced. It's about £15 for the year. An average petrol car costs about £200 a year in servicing."

Musk's Tweet also prompted a flurry of speculation about driverless technology, particularly Tesla's semi-autonomous Autopilot software which uses radar to enable cars to "see" obstacles and dangers in their path, switch lanes, brake and park unaided.

Unfortunately, 2016 has not been a good year for Autopilot. In January, 23-year-old Gao Yaning was killed when his Tesla smashed into the back of a road-sweeper in China. Investigators said they could not be sure Autopilot was engaged at the time, but there was no evidence that the car's brakes had been applied.

In May, the software hit the headlines again when 40-year-old former Navy SEAL Joshua Brown died while driving his Tesla Model S in Florida. The Autopilot function was activated but failed to detect an oncoming lorry. The Tesla ploughed into – and under – the vehicle, killing Brown instantly.

Undeterred, Musk was back on Twitter on Friday retweeting a link to an article reporting that "early automobiles caused as much controversy as driverless cars do today".

One trade publication suggested Musk might announce "upgraded cameras or improved sensors" for Autopilot which could be retrofitted to existing vehicles or installed on future Teslas.

However, Musk himself recently spoke of the need to extend driverless innovation beyond private cars and commercial vans to the wider transport industry, with a vision for self-driving buses and haulage vehicles.

In August, he wrote: “In addition to consumer vehicles, there are two other types of electric vehicle needed: heavy-duty trucks and high passenger-density urban transport."

Both were "in the early stages of development at Tesla", he added.

Of course, Musk insists tomorrow's launch product is "unexpected by most", so perhaps industry watchers should be thinking outside the box.

Doug Robertson, chair of the Electric Vehicle Association Scotland (EVAS), said he suspects the revelation might relate to an innovative new battery chemistry using so-called "miracle material", graphene.

Graphene was first extracted from graphite and isolated by scientists in Manchester in 2004. It is 200 times stronger than steel yet incredibly flexible. It also the thinnest material on Earth at just one atom thick - one million times thinner than a human hair - and a superb conductor. It is estimated that a graphene battery could charge a smartphone in seconds or an electric car in minutes.

Musk's arch-rival - Danish entrepreneur and founder of Fisker Automotive, Henrik Fisker - said earlier this month that he was developing a new graphene battery which would cut charging time and extend his next electric vehicle's range to 400 miles per charge.

Mr Robertson said: "Fisker sees himself as another 'big beast' in Silicon Valley - a combatant to Musk. 

"He's been very cagey with his details but he is claiming quite dramatic increases with energy storage density - you're talking about factors of six times what the current lithium-ion chemistry can achieve.

"It means the battery can store more energy and it's lighter, so obviously the lighter the battery pack the lighter the car, the further it goes. So it's all exciting stuff.

"Maybe that's what Musk has cottoned onto? He might just have pinched the technology, or maybe he's been developing it himself in parallel - I don't know.

"But there's a great push to use graphene because graphene has exciting advantages. It's a possibility - and Musk likes to steal a march on rivals."