Slightly unfair to state that a hybrid will flatten it’s batteries when used on longer journeys. A (non plug-in) Hybrid will always have a third to half battery capacity on the motorway. A roll down a downhill slip road will increase my battery charge by 50 percent. Honda’s latest hybrid will go into EV mode at over 70mph, albeit for a short time. Plug-in hybrids, for example Mitsubishi PHEV, will run on petrol only once the battery has been depleted simply because it’s regenerative capability nowhere near matches the battery capacity.

That maybe, but you're using kinetic energy that would normally have been used for the car just to coast (a non-hybrid car) and not use any fuel that now means you do. All you're doing is using petrol to charge the battery. My point is that when it's going on a motorway, the petrol engine will, for the most part, be the only thing in use as the battery would be depleted quickly if it was in constant use without taking power away from the IC engine.

With plug-in hybrids, their optimal use very much depends on the distance between charges and thus how often the IC engine gets used.

In town with a reasonable amount of braking, this makes far more of a positive difference than on faster moving roads, which is why hybrid cars achieve their best mpg (compared to IC engined cars) when run in urban areas. That's why minicab drivers use them for urban work, and they predominantly doing long runs in more rural areas use diesels: they are used for what they are most suited to.

All I'm trying to say is its horses for courses - it's just not correct to say 'hybrid or EV cars are green or better than IC engined cars' across the board. As the tech improves, especially around the generation of the electricity for plu-in hybrids and EVs (still some years off), maybe.

Does anyone on here own a plug-in hybrid privately?

As you imply, they make sense as company cars (at least currently) because of the lower BiK: but to buy orivateky they are so much more expensive than the equivalent petrol versiom that any payback period (through lower running costs) would be unrealistically long.

OK for high-mileage drivers? Maybe, but using the Audi A3 as an example, the 1.4 or 1.5 petrol will give you up to 55 mpg on a long run, where any hybrid isn't at a great advantage.

There seems to be some confusion over the way regenerative braking works. When a vehicle is travelling at a constant speed it has kinetic energy. If it needs to use its brakes, some of this energy is either recovered (by regenerative braking on a hybrid or electric) or lost as heat in the braking system. Travelling at a constant speed, a hybrid does not use its battery at all so it is in effect a fully petrol/diesel vehicle. However it's not quite that simple. A hybrid system generally keeps the battery at roughly half charge so it still has capacity to give an acceleration boost if needed, or absorb some extra charge when braking. Therefore if you brake suddenly say on a motorway, it will then use some of that extra charge to help you accelerate again until the battery is back to roughly half charge. If you come off a motorway and judge the car's momentum well, you may find that you hardly need to use the brakes at all, so a hybrid's advantage is reduced substantially. That's why urban driving shows a hybrid at its best. Lots of braking is unavoidable. If you live in a hilly area the hybrid will again have an advantage. There are other advantages in urban areas. A cabby I spoke to in Glasgow said one of their biggest savings was on replacement pads/discs.

Exactly guys.

People are forgetting on the efficiency front that hybrid engines usually run on the Atkinson cycle. This means they are very efficient. They can only do this because the electric motor is there as a booster when you need the extra power/torque.

At least as far as the Toyota is concerned this is one of the reason they are very good on fuel - the engine can be designed and run in a mode it couldn't in a conventional non-electric assisted car.

If you do a lot of town driving and like an auto they are very, very good. They're much quieter and work much better in creep traffic than an auto stop/start conventional car.

I'm way more familiar with the Toyota system and the Prius is about the most reliable long term car you can buy. Go to poorer countries - particularly in Asia - somewhere like Cambodia - and about 50% of the cars are (used, older) Priuses because they haven't got the infrastructure to repair and maintain complicated diesels or many petrols.

In a Toyota hybrid a gentle press on the brake pedal sends the power gauge into charging mode and sends power to the high voltage battery. Doesn't matter what you call it, but the car slows down and energy is saved to help out next time you accelerate.

ONLY IF the battery is not fully charged.

The battery routinely operates to only 80% capacity which gives a bit of leeway to accept an extra charge.

No: that is the limit to which it is charged ..