Let's talk about the E in EVs. The electricity. Where's it going to come from?

Can wind and solar provide enough power to charge our batteries? Can it be reliable enough? Or will this end in a terrible irony - that we have to use *more* fossil fuels, simply to drive the cars which were meant to decarbonise motoring? 

In this episode we look at whether renewable energy can keep track with a mass transition to EVs. What happens if the whole plan (electric cars = clean transport) gets out of kilter? Would we be better off encouraging people to keep driving their old, small, ICEs? And does the whole project rely on flawed assumptions about behaviour change - like doing your laundry overnight?

Our special guest is Kathryn Porter, founder of Watt Logic, and one of Britain's leading energy analysts. 

Could nuclear power be the key to sustainable motoring? We don't mean putting atomic reactors under car bonnets. What we mean is: whether nuclear power could generate electricity so cheaply it could be used to mass-produce biofuels. They work in conventional engines, and altogether this could make it much easier to  decarbonise motoring. 

So far so logical, but is it achievable? That's the question we discuss with Dr Tim Gregory, nuclear chemist and author of ‘Going Nuclear - how the atom will save the world’.

What does the explosion of AI mean for the electrification of motoring? Will there be enough power to sustain both? And if push comes to shove, won't governments prefer sexy data centres to humdrum EVs?

That might well be true of Donald Trump, who's making hay from a pushback on eco-policies in the US - where, as it happens, sales of hybrids are on the rise.

The US seems happy to let the best tech win, while the UK and Europe have put all their chips on BEVs. But in the long run - which will prove better for sustainable motoring?

We discuss all those topics and more with special guest Tammy Klein, chief exec of Transport Energy Strategies, in Washington DC.

What happens to taxes on driving when we stop using petrol and diesel? Governments will have a big fiscal hole to fill. One answer is road pricing for electric vehicles. But will it put people off BEVs? And would motorists baulk at having their mileage tracked?

With special guest Michael Dnes, road-pricing advocate and former senior official at the UK Department of Transport.

We've heard about the big idea - taxing cars by weight and mileage, not engine type. We've looked at the science, the money, and the practicalities? But what about the politics? What could persuade governments to revolutionise the vehicle taxation system? How could this concept overcome the scepticism of the press, public, and politicians who don't like meddling in the costs of driving.

Those are the big questions we explore in this final episode of series 2.

So how would this radical new system work in practice? How much would motorists actually pay? Would petrol still be taxed, too? And could you cheat your way around it?

Those are the questions Nick and Felix set out to answer in episode three of our second series.

Their new book - Critical Mass - explores the concept of taxing cars by weight and miles driven, not by type of engine.

Oliver's here to 'stress test' their proposition, and see if their answers really stack up.

In the last episode, Nick and Felix pitched their big idea - to tax cars by weight, not type of engine. They say mass is the critical environmental factor, in an electrified world of motoring. But what's the science behind it? Do the sums and formulae add up? That's the subject of this second podcast of series two.

We're joined again by Felix Leach, Associate Professor of Engineering Science at the University of Oxford. He and Nick are the authors of a new book - Critical Mass: The One Thing You Need to Know About Green Cars.

And Oliver's on hand, too - to put Nick and Felix through their paces.

Tax cars by a formula based on weight and miles driven. That's the concept we're explaining in our second series, where we're joined by Felix Leach, Associate Professor of Engineering Science at the University of Oxford. He and Nick are the authors of a new book - Critical Mass: The One Thing You Need to Know About Green Cars. It unveils a radical new concept in sustainable motoring, and how to harmonise it with governments' need to raise revenue. But how would it really work? Oliver's on hand to put Nick and Felix through their paces.

Nick and Oliver's special guest is John McElroy, host of the Autoline webcast and one of the world's most respected automotive commentators. There's lots to discuss. How can the US electric vehicle industry compete with China's? Will the growth of EVs actually reduce emissions? And can you cope without cobalt?

Nick and Oliver are joined by James Court, chief exec of the Electric Vehicle Association of England. They discuss - is it better for the environment if *everyone* gets an electric car? What's needed to make EVs better to own and drive than petrol/diesel vehicles? And if electric cars are cheaper to run, why do people call for subsidies?

Nick and Oliver are joined by EV expert Ade Thomas - creator of World EV Day and the Ebike Summit, and publisher of ElectricDrives. On the agenda - how do you choose the most environmentally-friendly EV to buy? What matters more - price, or range? And as software becomes ever more important, will models become obsolete more quickly?

All kinds of alternative fuels are appearing on the market - made from plants, vegetable oil, waste plastic, or synthesised. In theory they provide a third route to decarbonisation - after battery-electrics and hybrids. Alternative fuels are clean and many work with standard petrol/diesel engines. So what's the catch?

The 2035 ban is looming for petrol/diesel vehicles in the UK and Europe. But there are signs - particularly in the EU - that manufacturers are pushing back. Several major car-makers are shifting emphasis away from electric and towards hybrids - or even traditionally-fuelled engines. How will regulators respond? Are we heading for a showdown? And who will blink first?

The US has quadrupled import tariffs on Chinese electric vehicles to a whopping 100%. But only China can make battery EVs at an affordable mass-market price. So does this spell trouble for taking the carbon out of American motoring? And how will Europe resolve its own dilemma? Resist China's EVs and say goodbye to the 2035 target? Or allow a flood of cheap imports, whatever the consequences?

Europe and the UK are set to ban petrol/diesel cars in just nine years' time. But with electric-vehicle sales falling - and production-capacity inadequate - the deadline looks increasingly unachievable. So what happens now? And why have policy-makers pushed the ban so aggressively?

You're buying a new car - how do you choose the most sustainable option? And what's better for the environment: a brand new electric vehicle, or extending the life of your old banger - even a 1936 Bentley? The answer to both questions is...it's complicated.

Tyres are the dirtiest part of your car. They generate 1,000 times more emissions than the tailpipe, and toxic tyre debris is poisoning waterways. But regulators have only just begun to grasp the problem. And there's a real conundrum - because electric vehicles are the worst offenders.

Hybrid vehicles generate more CO2 than full battery-electrics - but less than traditional internal combustion engines. Compared with electrics, hybrids are cheaper, and you don't have to charge them - which makes the vehicles an easier proposition for consumers. But then again...they still use petrol. So where should the focus be? That's the question Nick and Oliver try to answer.

Nick the emissions analyst, and Oliver - then a Volkswagen exec - used to be on opposite sides of the fence. Here's how they met, crossed swords - but then found common cause.