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« A new fusion process | Main | A bloody truth or a big bloody truth »

Hybrids and the cost of virtue signalling

Readers will be much amused by the recent report from consultancy firm Element Energy (see bottom of post). Prepared for Lord Deben's Committee on Climate Change, it describes the gap between real-world performance of motor vehicles and what happens in the test laboratory - a topical subject, I'm sure you will agree.

The report's main theme is that manufacturers are gaming the rules of the test procedures to make their cars appear to perform better than they will do in real life. The performance gap could be as much as 50% in a few years' time although it is expected to shrink when new performance standards come into play.

What caught my eye was the discussion of hybrids. The official tests assume that hybrids are driven in electric mode for two thirds of their mileage. The reports authors' reckon that it is rather less and suggest that, as a result, the overall carbon emissions could be as much as 50% higher than suggested by the test results.

But it gets worse. The authors reckon that in the real world, drivers don't stop to recharge the batteries - they drive on the petrol engine. Apparently in the Netherlands surveys have suggested that there may be a 200% gap in emissions performance between the real world and the test results because of this effect. The authors suggest that the figure may be lower elsewhere, perhaps of the order of 100-150%. In essence, for much of the time, hybrid drivers are carting around a run-down battery that they don't use - it's the hidden cost of virtue signalling if you like.

The report concludes that even in the real world, emissions from hybrids are much lower than from conventional cars. Of course this involves completely ignoring the emissions produced in the production of electricity. Given the share of fossil fuels in the UK's electricity generation mix, it is quite likely that hybrids are generating more carbon dioxide emissions than conventional vehicles.

But unfortunately, this seems to have been beyond the scope of the report.



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Reader Comments (46)

When I did a commute Derby-Coventry every day, in an old Citroen diesel I often wondered who was being more environmentally friendly, me or the Nissan Pious' which overtook me doing 80mph. As the commute used about 2 gallons a day I used to cruise as economically as possible, rarely if ever did I pass a hybrid although lots overtook me.

This confirms my thoughts, the battery is an additional load when commuting on the motorway.

Oct 1, 2015 at 10:57 AM | Unregistered CommenterSandyS

"beyond the scope of the report"

Beyond the scope of DECC's (or Gummer's) ability to think...

Oct 1, 2015 at 11:03 AM | Registered Commenterjamesp

Why do governments ever generate rules if they don't sit down beforehand and work out how those rules will be circumvented, monitored and enforced? The EU in particular is a sod for this. That's why the UK is always in trouble with them. We ask inconvenient questions and we're seen as trouble makers. A few years down the line it turns out nobody but us is coming even close to policing the thing. On the issue of cars it seems all governments have been playing let's pretend. Why bother with the rules in the first place? I can only conclude it's like speed limits - whatever you set them to, many people will go above them a little bit.

It all means that body knows what they have to stick to or not. People continually test the boundries to see if they can get away with something. VW now know the answer to that question.

Electric cars are the latest political self indulgence. They need extra deception to get them off the ground.

Oct 1, 2015 at 11:03 AM | Unregistered CommenterTinyCO2

A letter of complaint about a Lexus 45h that its fuel consumption at motorway speeds was 21mpg. Answer, at 70mph the petrol engine (4500cc) does all the work and has to carry the extra half ton of batteries.

Oct 1, 2015 at 11:05 AM | Unregistered CommenterJohn Marshall

What counts as a "real world" test? We get 50mpg on the motorway and 30mpg or less when driving around town. Both are "real world"; both are experienced in infinitely variable proportions; both are sensitive to gradients, to wind direction and to weather conditions. There is no "real world" test, only our real world experience - and it will be different from everyone else`s experience and each time we drive our car it will be different too.

Manufacturers have no choice but to test their vehicles to the prescribed test criteria and to meet them, otherwise they cannot sell said vehicles or owners must pay more tax. Any comparison with my real world experience is entirely coincidental. The test criteria have been tightened over the years. Perhaps more useful data could be obtained if testers compared current vehicles with earlier generations to check out what the differences are.

Oct 1, 2015 at 11:07 AM | Unregistered Commenteroldtimer

You seem to be talking about plug-in hybrids here but refering to all hybrids. Conventional hybrids that don't plug in charge themselves from regeneration and surplus engine power so are much closer to the official figures.

Also the idea that a hybrid has no advantage at motorway speeds is a myth. I have a Lexus hybrid and at 70mph it switches between charging and discharging the battery even though the engine is constantly running. Even though it has a 2.5 litre petrol engine it gives about 55mpg on motorway runs. Overall it uses about half the fuel that my previous 2.5 litre petrol car used.

Oct 1, 2015 at 11:10 AM | Unregistered CommenterGary

O/T a little, but related to cars and the VW scenario now playing out.

VW have announced recalls to update the software with the cheat code.

So in 2 weeks they have managed to produce a legitimate piece of software, but could not do this in the entire development cycle. Really?

Oct 1, 2015 at 11:17 AM | Unregistered CommenterRockySpears

I can't understand why these days people need cars with such big engines. My Honda has a 1340cc i-VTEC engine and 6 gears and gives me all the power I need, and good fuel economy.

Oct 1, 2015 at 11:49 AM | Registered CommenterPhillip Bratby

You are partly right but there is a bit more to the EU question than you imply.
Most EU Directives are the result of some sort of compromise between the various departments and are framed in such a way that individual countries can interpret them in a way that coincides with their interests. (You could say "to suit themselves" but that sounds as if they are trying to get away with something that they shouldn't which is not the case in reality.)
The problem that the UK has is that Whitehall insists on interpreting EU DIrectives literally and applying them to the full regardless (in some cases, as Booker has pointed out more than once, even when there are businesses or categories of business that they were never intended to apply to). It is this more than anything else that pisses off the rest of Europe because there is at bottom no reason why the UK should demand a derogation from Directive xxxx/2015 when all they need to do is to interpret it properly!
(A bit OT: the reason why the UK is at loggerheads with Europe about immigration is that it insists on having better deals on benefits than the rest of the EU and also refuses to introduce any form of identity document which makes it super-attractive as a place to sponge and work on the black market! A smidgin of "meet me half way" wouldn't come amiss.)
None of this excuses VW's cheating but there would be less of a problem in our situation vis-à-vis the rest of Europe, if not the rest of the world, if we weren't so prissily hypocritical about things. "Setting in example" is another aspect!.
Sorry. Today's rant over!

Oct 1, 2015 at 11:52 AM | Registered CommenterMike Jackson

Beyond the scope or beyond the remit of the report? Any study in the efficiency of hybrids MUST include the energy & environmental costs of the electricity generated to power the 'low emission' hybrids. To fail this basic requirement highlights this report as being yet another exercise in orchestrated greenwash.

Oct 1, 2015 at 11:57 AM | Unregistered Commentercheshirered

oldtimer asked

"What counts as a "real world" test? We get 50mpg on the motorway and 30mpg or less when driving around town. Both are "real world"; both are experienced in infinitely variable proportions; both are sensitive to gradients, to wind direction and to weather conditions. There is no "real world" test, only our real world experience - and it will be different from everyone else`s experience and each time we drive our car it will be different too. "

The best answer I can give you is to point to an online database that uses information supplied by real people driving real cars.

When you input your value you are asked for your driving type with the options City/Mixed/Motorway

The interesting thing I see is how the levels of accuracy of the claims have DECLINED in the last decade.

As an example consider the VW Passat

2005 2 litre Tdi Real Mpg - 46.8 which is 93% of the claimed value
2015 2 litre Tdi Real mpg - 52.5 which is 75% of the claimed value

For the petrol engined versions we find

2005 2 litre FSI - Real Mpg 36.6 mpg which is 105% of the claimed value
2011 - 1.4 litre FSI - Real Mpg 39.7 mpg which is 87% of the claimed value
2015 - Petrol engine versions dropped

Bottom line is we are seeing large increases in claimed miles per gallon which are not reflected in the
values reported by users. The web site shows the number of reports for each type. 240 in the case of the Passat.

The Prius has actually gotten worse since it was launched.

The 2012 Prius got an average of 52.7 mpg (79% of the claimed value)
The 2003 Prius achieved 53.8 mpg (85% of the claimed value)

Before anyone asks I have no personal or business connection to 'honest John'

Oct 1, 2015 at 12:07 PM | Unregistered CommenterKeith Willshaw

Yes, but they haven't said how big the performance hit will be...

Oct 1, 2015 at 12:09 PM | Unregistered CommenterJohn Davis

Phillip Bratby: A 1340cc Honda (I'm guessing Jazz) may suit you but that doesn't mean it suits everyone. In the past I've found that big lazy engines are much easier to drive than small hard worked ones without much real world fuel consumption penalty. Nowadays, however, with the CO2 obsession taxing large engined cars heavily you have to play the system. I tried a diesel but didn't like the horrid thing but have found that a hybrid with a largish engine suits me fine, decent economy, smooth drive and low tax.

Oct 1, 2015 at 12:09 PM | Unregistered CommenterGary

If I stick a defunct petrol engined generator in the boot of my VW, can I call my VW a hybrid, even if I never use the generator to power anything at all?

I could put some meaningless stickers on the car, to let other road users know how meaningless my Green credentials are.

Oct 1, 2015 at 12:11 PM | Unregistered Commentergolf charlie

RockySpears, people bought their VW's because they were 'clean' and performed well. Now they are going to get modifications to make them perform clean. There may be complaints that they don't perform. Whether they are less economical, and burn more fuel for the same mileage, now that they are 'clean', will raise questions about the advantages of economy over 'clean'. Surely 'clean' burn should mean better efficiency and hence economy?

Oct 1, 2015 at 12:21 PM | Unregistered Commentergolf charlie

Mike Jackson, and I don't disagree with you. It's one reason for leaving the EU, so that we know when it's Europe making rules and when it's our own paper pushers.

Oct 1, 2015 at 12:29 PM | Unregistered CommenterTinyCO2

I could put some meaningless stickers on the car
It's been done before. They used to be called "go faster stripes"!
Incidentally cheshirered has got it wrong. There is no need to "include the energy & environmental costs of the electricity generated to power" anything that carries the Green Seal of Approval. There are no such costs. (Actually there are but "these are not the costs you are seeking". - © Obi-Wan Kenobe)
If electricity is generated for any purpose not carrying the GSA or oil or gas or coal is used for any other purpose then all environmental costs MUST be added into the price. Failure to do this means that the product is being "subsidised". By the same taken anything which does carry the GSA cannot be said to be "subisidised" since the word has connotations which can never be applied to something patently beneficial to humanity which all GSA things are by their very nature.
And if you disagree I'll set Shukla on you!

Oct 1, 2015 at 12:31 PM | Registered CommenterMike Jackson

Rather than ever more tricky testing regimes that manufacturers will still optimise for, perhaps it would be better to operate a jury pool of bog standard people to drive new cars as they go about their business and average the results.

You would also need to simplify (or remove!) the tax bands for car emissions as they could no longer be considered to be precise. They mostly go up in 10 g steps. It is nudge politics reliant on a level of accuracy that has no relation to the real world.

Oct 1, 2015 at 12:43 PM | Unregistered CommenterGareth


"recalls to update the software"

To what end - to make it run so lean that it's undriveable? I'm damn sure if my car was recalled for a software update in these circumstances, I would avoid it!

Oct 1, 2015 at 12:54 PM | Registered Commenterjamesp

I have a diesel Skoda which I will not take in for the mod unless it means it cannot pass the MOT!

Oct 1, 2015 at 1:23 PM | Unregistered CommenterBill

If anybody wants to see what the vehicle test houses have to do to reach emission compliance...try this from a short way in - Page 5:

Supporting Analysis regarding Test
Procedure Flexibilities and Technology
Deployment for Review of the Light Duty
Vehicle CO2 Regulations

Oct 1, 2015 at 1:23 PM | Unregistered CommenterEx-expat Colin

I have a diesel Skoda which I will not take in for the mod unless it means it cannot pass the MOT!

Oct 1, 2015 at 1:23 PM | Unregistered CommenterBill
What happens about the VED I wonder
With the '"beat" software being removed wouldnt this now make tail pipe CO2 emissions greater than specified for the vehicle thus an automatic fail for the MOT ?

Oct 1, 2015 at 1:42 PM | Unregistered CommenterBLACK PEARL

A previous episode came to mind:

Oct 1, 2015 at 1:57 PM | Unregistered Commenternot banned yet

Mike Jackson, 'Go Faster Stripes' were reliable reported in pubs everywhere to take at least a second off your 0-60 time.

They were mainly red, and bits of blue and black. Green has never been a favourite colour, for anybody wanting to get anywhere.

Oct 1, 2015 at 2:10 PM | Unregistered Commentergolf charlie

Both my wife and I drive conventional hybrids (mine a Camry her car is a Fusion) and have for about six years. I would echo Gary's comment, since we see a significant improvement in mileage - about 40 mpg (US gallon), relative to about 25 conventional - on average over the years -so that we fill up about every roughly 4-500 miles. There is a constant interplay between the electrical and conventional drive, and while in the short term gas prices are down, I still expect that we will recoup more than the price differential from the reduced gas consumption (which carries with it the consequent reduction in emissions).

Oct 1, 2015 at 2:56 PM | Unregistered CommenterHeading Out


> wouldnt this now make tail pipe CO2 emissions greater than specified for the vehicle thus an automatic fail for the MOT ?

As far as I know the "cheat mode" would apply to everyday driving rather the the normal mode applying in tests.

This means the cars performance will be drastically reduced.

Oct 1, 2015 at 3:09 PM | Unregistered CommenterTerryS

I do find the claims for hybrid cars a little bit bemusing. By definition they must be heavier than conventional cars of the same power, and hauling that load round isn't free.

Yes, when they go down hill they can coast and charge the batteries, but they had to have the extra weight hauled up hill to begin with. Yes, they can have regenerative breaking, but they also have anti-regenerative acceleration, f = ma as I was taught at school.

What are the benefits of a hybrid car exactly over and above switching off the engine when breaking, when going down hill, and maintaining a coasting speed by overshooting and undershooting the target (e.g. to drive at 60, stop the engine at 70 and restart the engine at 50)?

Comparing current mpg with a previously-owned car is not meaningful in any way, because all ordinary cars have improved a lot with time.

Oct 1, 2015 at 3:25 PM | Unregistered CommenterMax Roberts

Heading Out

Have you factored in the replacement of batteries in the overall running costs ?
Nissan Leaf all electric over here replacement battery at £5000 less £1000 of the depleted units
As far as CO2 emissions the amount expelled in just making the battery equal that of producing a compact car which defeats the intent of 'saving the planet' with this tech in the first place
As far as short term gas prices are concerned, with the advent of shale only just being tapped globally + if Iran is allowed to be a major producer once more, it could be lower gas prices for years to come.

Oct 1, 2015 at 3:38 PM | Unregistered CommenterBLACK PEARL

Max Roberts: When a normal car is braking that energy is disapated as heat, on a hybid pressing the brake pedal initiates regeneration charging the battery, it only activates the mechanical brakes at low speed. In addition the engine is used to charge the battery, often when it would be otherwise wasted such as idling when warming up from cold start. With Toyota and Lexus hybrids further efficiencies come from using an Atkinson cycle engine and using the electric motor to fill in the for the lack of low rev torque that results. They also use Power Split Device rather than a conventional gearbox which acts as a continuously variable transmission, allowing very low revs at speed (1200rpm @70mph on my car) when load on the engine is low. It is in effect doing what you describe shutting the engine on and off but without changing road speed. Below about 45mph the engine stops and starts, above that it always runs but often at low revs.
Regarding comparing mpg with a previous car, fine, show me a current car with a 2.5litre petrol engine and automatic transmission that can achieve an actual 45mpg around town and 55mpg on the motorway. there are diesels that can do it but I don't know of any petrols with similar performance.

Oct 1, 2015 at 4:02 PM | Unregistered CommenterGary

Benefits of an electric car.

Great if you are not paying for the electricity, and if you do not really care how the electricity is generated. Thos in SE England may be getting their electricity from nuclear France

Oct 1, 2015 at 4:50 PM | Unregistered Commentergolf charlie

Black Pearl:
By the time we exchange cars (which is getting closer for the Camry since we have had it for a couple of years more) the value of the trade-in is almost nothing relative to the price of a new car, and since we expect to trade before we need to replace the batteries it doesn't enter into the calculation.

Oct 1, 2015 at 5:30 PM | Unregistered CommenterHeading Out

Keith Wilshaw: "The 2012 Prius got an average of 52.7 mpg"

The modern diesels with auto-stop/start, 8 speed auto gearboxes, and eco-modes, can get similar mpg figures. My 2 litre BMW M3 has got an average 54mpg from new, in mixed motoring, since January this year.

My beef against electric and hybrid cars is that if the £5,000 government subsidy which they attract were applied to diesel cars like mine and used for pollution control devices, then there would be no problem with diesel at all.

Oct 1, 2015 at 5:41 PM | Unregistered CommenterSteven Whalley

I drive a Lexus CT200h. I don't care about virtue signalling and certainly disbelieve the theory of CAGW.
However, around town I get 45mpg real world usage which seems fairly ok.
On top of that the tax was written off in 1y (saving me £12k in tax that year).
I pay zero road tax and zero congestion tax.

And it's really fast from 0-20mph so is actually v nippy in city traffic.

Overall I'm v happy and will probably drive it until it is written off.

Oct 1, 2015 at 6:22 PM | Unregistered CommenterOnion

Bishop's comment is true for plug ins, but not for conventioan full hybrids like Prius or Fusion. The Chevy Colt plugin is rated combined averge 60 MPG equivalent. The truth is about 35 mpg. The EPA mistakes are dissected in the Volt example in The Arts of Truth.

Oct 1, 2015 at 6:51 PM | Unregistered CommenterRud Istvan

Golf Charlie:

Or from coal fired Maasvlakte if you're in Essex...

Oct 1, 2015 at 7:27 PM | Unregistered CommenterIt doesn't add up...

the value of the trade-in is almost nothing relative to the price of a new car, and since we expect to trade before we need to replace the batteries it doesn't enter into the calculation.
Oct 1, 2015 at 5:30 PM Heading Out

If the value of the trade-in is negligible, doesn't that say something quite significant about the remaining life, and the replacement cost, of the batteries?

Oct 1, 2015 at 7:35 PM | Registered CommenterMartin A

Keith Willshaw
My old Citroen Xantia 1.9TD gets in excess of 50mpg and I only use it for non-motorway driving. That's without the help of much in the way of computer aided economy. I would hope that it would lose out to a hybrid in urban driving, but when using it to get to work in Beeston Nottingham with traffic going at a walking pace it used to keep pace in first gear at tickover, walking pace cruise control, so it might be a close run thing in that situation. I tried to avoid coming to a halt as much as possible.

Honest John, I used to read his Telegraph agony aunt column every week. Online it is a good source of information from the real world. When buying a second hand car it's always worth reading his review of the vehicle. I have input my own mpg figures in the past. I too am only a user of the website.

I'm not sure about petrol cars but modern diesels use no fuel going downhill with zero accelerator pressure. This can be checked on the on-board computer set to Litres/100km which will read 0. A small right foot input to maintain speed will increase the figure but it will still be low. I suspect careful driving will be better for the environment and pocket than heavy footed use of a hybrid

Oct 1, 2015 at 7:54 PM | Unregistered CommenterSandyS

Gary, I know perfectly what regenerative breaking is, there is a long history of never quite getting it to work on the London Underground. On the other hand, do you know the energy costs of hauling those extra batteries everywhere?

And, I pointed out that the benefits of better engine and transmission management alone are not being considered in isolation of the batteries.

Oct 1, 2015 at 7:59 PM | Unregistered CommenterMax Roberts

Max: All I know is that I have a car that gives similar economy and performance to an equivalent diesel engined vehicle for a similar cost and much greater refinement. As a benefit, NOX and particulate emissions are much lower without complicated reduction measures and I don't have the potential of expensive repairs to turbos and dual mass flywheels. as for the additional weight of the battery, my hybrid weighs 75kg more than the non-hybrid version so its equivalent to an additional passenger.

Oct 1, 2015 at 8:52 PM | Unregistered CommenterGary

Braking Not Breaking. tssst

Oct 1, 2015 at 8:55 PM | Unregistered CommenterMatt

What is the longest extension lead for an electric car?

Could city centres have overhead power lines above the roads, so cars could be powered direct, just like the old trams that were phased out because ..doh!

Could all city centre petrol stations be converted to stables, with hay racks, just like .....doh!


Oct 1, 2015 at 9:31 PM | Unregistered Commentergolf charlie


How many miles have you got on the Xantia
Used to have one of the earlier models but 130,000 miles, issues with leaks on fine tubing on the high pressure suspension system and the car scrappage scheme coming along at an opportune time resulted in the old 'Black Pear'l being sent to Davy Jones Locker

Oct 1, 2015 at 11:41 PM | Unregistered CommenterBLACK PEARL

I am far from convinced that fuel consumption has greatly improved over recent decades. I consider that engines are a little more efficient but the benefit of that can easily be off-set by driving style, and most people drive needlessly aggressively. Most people always seem to be in a hurry.

When I learnt to drive, I was told that if you expected to be stationary for more than 7 seconds, one should switch the engine off as that would save fuel. It is a habit I have stuck to for most of my life. If I am in a queue and the road slopes slightly downhill, I will always switch my engine off, so too with traffic lights unless I know the sequence and I expect them to change imminently.

In order to get good fuel economy, one needs two things. Low weight (this is particularly important for urban start stop driving) and good aerodynamics (particularly important for fast motorway driving). What has happened is that over the years cars have significantly increased in weight, and with the change to SUVs, the aerodynamics has, on average, gone backwards.

I bet that a Lotus Elan of the 1960s weighing about 700kg and with good aerodynamics and with an overdrive gearbox would competitively match many tin boxes of today in most driving conditions below 80mph.

Indeed, I recall seeing a road test on a 1960s FIAT Arbarth Zagato 1000cc which had 0-60mph in about 6 secs, a top speed of over 125mph and would return over 65mph (I think that it was just under 70mph). but then again, it weighed only about 500kg whereas today, most small cars come in at 1150 to 1200kg. The car was a glorified motorbike, but stunningly beautiful to look at. The looks were probably necessary since I suspect that it would break down a lot so one was left to stare a lot at the fickle Italian mistress. It is in reliability and ergonomics that modern cars have improved.

Personally, I thought that everyone knew that the test data was divorced from the real world and should be taken with a large pinch of salt, so I am surprised that recent news has come as a shock.

Oct 2, 2015 at 2:18 PM | Unregistered Commenterrichard verney

I just want to echo what Gary has been saying. I drive a Prius quite often because I love the mileage I get. The exact number depends on a variety of factors (particularly how fast I choose to drive), but it's rare I even see it under 50mpg. I think the only time I've ever seen it under 45mpg was when I decided to test its mileage during a roadtrip and set my cruising speed at over 80mph. Even then, it hovered at 42-43mpg. I'm happy with that.

Oct 2, 2015 at 8:04 PM | Registered CommenterBrandon Shollenberger

I recently drove from England to Spain via Holland, Germany France and Andorra in an old 3 litre diesel, and until I got to Andorra, I was averaging just a little over 50 mpg.

Andorra was all 2nd and 3rd gear driving and that really knocked the consumption, but I still finished the trip with a consumption of over 46mpg, Incidentally, Andorra was selling diesel at about 98 cents per litre when the £/€ exchange rate was about 1.38 so about £0.71 pence a litre!

Of course what NO2 (and other particulates) emissions the car chucked out is another matter, but certainly there can be no doubt that diesel does provide very good fuel economy, and on the continent diesel is cheaper because it is not taxed as heavily being seen as a commercial fuel and it is sensible to not needlessly inflate the costs of business (all goods having to be delivered to market).

In mixed driving, I tend to get mid 40s out of my 3 litre diesel. Of course, there are plenty of modern day diesels, especially small engine ones that return 60 to 70 mpg, but I am happy with mid 40s, and this compares very favourably with the Golf GTI that I had which would return only about mid 20s in similar mixed driving conditions. Of course, with the cost of petrol (which is mainly tax), everyone would like a car that returns over 100mpg, but if that were to happen, the government would put up the price of fuel since it needs the taxes levied on fuel.

There is no need for hybrids. they are not green, and they produce just as much CO2 as a petrol car. The government and car salesmen overlook the CO2 produced in the electricity needed to charge their batteries. The CO2 figures for hybrids is a gross misrepresentation.

Of course, there is a case to be made for pollutant free vehicles for city use. It being understood that such vehicles are not pollutant free, but that they do not emit pollutants at source when driven. The pollution is being emitted out of town at the power station, or the place where the batteries etc are manufactured etc.

Oct 3, 2015 at 4:38 AM | Unregistered Commenterrichard verney

Richard: You seem to be misunderstanding, there are two types of hybrids, those that can be plugged in and those that only re-charge their batteries on board from the engine or by regeneration.

Non plug-in hybrids can have diesel or petrol engines, the petrol ones have similar fuel consumption to an equivalent performing diesel, diesel hybids give slightly better consumption to their straight diesel counterpart. Their co2 output is directly related to their fuel consumption as there is no other energy input. Typicaly they can manage a couple of miles running on electricity alone but that is not the point of them.

Plug-in hybrids differ in that they have a larger battery which can be charged from an external source and they can run greater distances on electricity alone, about 20 to 30 miles. When the battery is discharged they run a a conventional hybrid although most currently available don't seem to be as efficient in this mode. The co2 figures for this type do not fully reflect the true situation as they don't take into account the external electricity used (nor do true electric cars either).

The problem that is being highlighted in the report refered to in the Bishop's post is that most users of plug-in hybrids are not actually plugging them in and therefore the actual emissions/fuel consumption is much greater than the official test figures suggest.

Oct 3, 2015 at 5:24 PM | Unregistered CommenterGary

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