Does your car achieve its official miles per gallon?

My car gets 60.47mpg¹.  How do I know?  Because I have recorded every litre of fuel put into it since I bought it three summers and four winters ago, and trust that the odometer gives me a reasonably accurate mileage driven.

So am I pleased – it does sound like a decent fuel economy, after all?  Well, not wholly, as although it is almost twice the number of miles per gallon of its predecessor, it is still a lot lower than the 85.6mpg the manufacturer's website would have you believe that I should be getting.  And if you've been sold a promise of fuel economy, to get a result that's almost 30% worse is more than a little disappointing. Of course, that also means I am pumping out 30% more CO₂, the main gas contributing to climate change, than I expected.

So does that mean I am a poor driver?  Probably not; when I shared a car with another driver I consistently got better consumption than she did, largely through more gentle acceleration.  I am always conscious of my consumption and try to avoid sharp braking, and hardly ever use the air-conditioning (which can be a huge draw on engine power, thereby reducing miles per gallon).  What it really means – and this seems to be an effect that is particularly pronounced with smaller more economical cars, that the official figures are wrong.

And how can this be?  Well, the official test figures are undertaken using something called the New European Driving Cycle (NEDC) test.  This places the test car on a rolling road, and a highly trained driver then drives as gently as he or she possibly can, to achieve the reported figures.  Moreover there are some tricks of the trade that be used to flatter the results.  Tyres may be over inflated to reduce rolling resistance; the car may be run in a higher gear than would be normal for the speed; special lubricants (and never oil that's been in the engine for a year) can be used, and weight is minimised by removing the spare wheel.  In extremis, the alternator may even be disconnected, the radio aerial removed or door handles and other protrusions taped over to reduce resistance.  All are apparently permitted – and of course there are no traffic lights, roundabouts, head winds or traffic jams to reflect reality.

A report from the International Council on Clean Transportation confirms this.  According to their website:

Comparison of official and "real-world" fuel consumption and CO₂ emission values for passenger cars in Europe and the United States, shows that the average discrepancy between them rose from less than 10% in 2001 to 25% in 2011.

The EU has got wise to this.  They realise that the tests, which are fundamentally unchanged since first introduced in 1970 no longer reflect reality and are too easily "gamed".  Instead they would like to introduce a new World Light Vehicle Test Procedure (WLTP).  However most manufacturers are opposing this, as they fear that they will be unable to meet EU-mandated fuel economy standards for new vehicles and incur huge fines.

I have some sympathy for the manufacturers, but not for their attempt to delay the introduction of WLTP and more realistic estimates of miles per gallon and emissions.  There have been great improvements in energy efficiency of private cars over the past couple of decades, as engines have been designed to burn more leanly, aerodynamics have been improved and weight has been reduced by the introduction of more plastics and composite materials.  And if moving to a new calculation basis means that the EU's targets, set using the old method, are unachievable in the timescale, then maybe the targets should be adjusted to match any adjustment between the old NEDC and newer WLTP methods.  But consumers should demand more accurate and realistic estimates of typical fuel consumption, rather than being given increasingly unrealistic ones.

This is important because comparisons are not made between cars, but between cars and other forms of transport.  If my official consumption implies lower CO₂ emissions for driving between London and Manchester than taking the train (which it does), I may well end up making a misguided choice if I want to minimise carbon emissions.  (And of course the official train consumption is not the marginal emission from my joining an existing train, but the average emissions across all passengers, but that's another story).  It also distorts comparisons between figures for fossil fuelled cars (like mine) and electric vehicles, not to mention my trusty bicycle…

Moreover, as the gap between official and typical miles per gallon has now grown so large (some commentators estimate that it has doubled in the last 7 years²) it risks bring the whole concept of an energy label into disrepute. If you can't believe car labels, why should you believe those on fridges or homes?  (And yes, I know that there is also a well known performance gap on homes in particular, but we can at least explain most of the difference from lifestyle choices. It's different with cars as we don't choose to drive at 30mph in top gear with the windows taped up…)

So the car manufacturers should get real and give us real estimates of fuel consumption and CO₂ emissions.  And who knows, in a future blog, I may even be able to claim that I have bettered the official consumption by 10%!

¹ The UK average figure, based on retail fuel sales into the domestic market of 27.4mn tonnes of retail motor fuel (approx. 7.02 billion gallons) and DfT estimates of 242.3 billion miles driven in 2013 works out at an unimpressive 34.5mpg. However this is about 4% better than the equivalent figure for 2008, showing that there has been some real improvement, bearing in mind that almost two thirds of the cars on the road today were also on the road five years earlier; it also includes some non-passenger vehicles when they refuel through retail outlets.

² The ICCT report says that "the gap was especially pronounced after 2007–2008, when a number of European Union Member States switched to a CO₂-based vehicle taxation system and a mandatory EU CO₂ regulation for new cars was introduced."

Calculating Carbon Footprints

Moving home often gives us a chance to take stock and think about all the changes since we first set foot in the old home. Moving websites can offer a similar opportunity for reflection, so as I have just moved the Simple Carbon Calculator (www.carbon-calculator.org.uk) I thought I would reflect on changes in that field.

By way of background, this Carbon Calculator (and there are others, I admit) has its origins as a challenge to myself and to support those in the Energy Efficiency Accreditation Scheme. Back in 2001, the UK's Department of Food and Rural Affairs (Defra) had not long published its first guidance to companies on calculating and reporting carbon dioxide (CO₂)emissions. Meanwhile, I had been tinkering with websites, and rather fancied seeing if I could convert their guidance into a simple calculator using a newfangled tool called JavaScript. So I took an open source bit of code and - necessarily - simplified Defra's factors a little to produce a basic calculator that you could enter energy use in normal units (kWh, litres, tonnes or other everyday values) and end up with a CO₂ value compliant with Defra's numbers.

Over the years, both Defra and I (quite independently, I must add) have enhanced the tools. But as Defra's has become ever more complex with over 4,000 conversion factors at the last count, I have tried to keep mine...simple. That's not to say that it's not useful; I believe that over 90% of households or companies could use the Simple Carbon Calculator to calculate their footprint within 5 minutes (assuming they had their energy consumption data to hand). And Defra's guidance notes and tables, along with 50 pages of assumptions are always available for the other 10%. (Incidentally the background paper, written by Ricardo-AEA is fascinating for use carbon nerds, but lacks the actual factors deduced from their discussions.)

This leads to a key point: calculating a footprint need not be terribly complicated; it's just a question of (a) having all the right data to hand and (b) knowing which are the right factors to use - and the aim of the Simple Carbon Calculator was to at least partly meet the second bit.

At the start, though, I said I would reflect on the changes to the actual calculation, rather than to website techniques which have rendered my old JavaScript "not modern enough" to stay on the previous host site.

First and foremost, the electricity factors have changed conceptually, twice, over the past12 years. When first created Defra thought it was best to use a marginal factor - ie. the emissions associated with generating an extra unit of electricity. In the UK, this was assumed to be electricity from a combined cycle gas turbine (CCGT) as they could be switched on and off most easily (try doing the same with a nuclear power plant...) However CCGT emissions (which were fixed for several years at 0.43kgCO₂/kWh) tend to be lower than average UK emissions (which included older gas stations and coal). So although it might be fine for a company or person at the margin, if you started adding up emissions from everyone calculated on this basis, you severely underestimated total emissions.

Recognising this problem, in the mid-2000s Defra moved to a five year rolling average. This captured longer term trends and wasn't unduly buffeted by abnormal power stations (such as nuclear power stations breaking down, which they seemed to have a distressing tendency to do). However over the past few years this has tended to lead to the opposite error, as coal power plants were mothballed and new zero energy generation - especially from offshore wind - has come on stream.

So, for 2013, we have all moved onto a prior year basis, on the grounds that the generation mix last year is probably the best indicator of what it will be this year. This has meant restating prior years (and miraculously losing emissions for the average user), but is probably the correct answer intellectually, unless someone can develop a 12 month forward weather forecast to estimate future wind energy production! However, we may find the downward trend reversing as US shale gas depressing the demand (and hence global price) for US coal, leading to more imports into Europe for power generation.

As you might expect, emissions for fuels (both gaseous and liquid) have tended to be less variable. However even there we find some trends emerging over the last 12 years. Natural gas, which once came almost wholly from the North Sea, is now increasingly coming in by ship from North Africa as LNG (Liquid Natural Gas) - as much as 20% in recent years. And although the Simple Carbon Calculator is designed for Scope 1/Scope 2 emissions (not full "Well to wheel"), Defra's factors do recognise the much larger carbon footprint of LNG.

Road fuels have also changed. Partly as a result of the EU biofuels directive, both diesel and petrol have a small biofuel component, and this has led to a slight drop in the carbon intensity of the fuel, as carbon from renewable sources is not included. That's not to say that biodiesel or bioethanol have anything like a zero carbon footprint; just that it's a bit lower than the equivalent fossil fuels.

Emissions from aviation are a great concern, as the fastest growing source globally. We have always known that the effects of planes flying at high altitudes was not just as simple as their CO₂ emissions, but that there were other effects, such as vapour in contrails that also exacerbated climate change. Well, finally this year Defra has accepted the arguments and included an uplift for "radiative forcing". Of course this means that for a typical middle class household flights are suddenly a much larger component of their carbon footprint...

As the calculator has grown in popularity I have added refinements and extra categories, while keeping to the concept of keeping everything on a single easy to use page. This year's enhancements included a much wider variety of default vehicles for those who know the approximate distances driven, but don't have records of fuel purchased. And, as an antidote to higher flight emissions, I have added Eurostar emissions - although these always seem unnaturally low as they are largely based on purchases of French nuclear electricity, and hurtling across Northern France at 300km/h may not be wholly environmentally benign!

So if this has whetted your appetite to find out your own footprint, I ought to tell you where the calculator has moved to. It's still at www.carbon-calculator.org.uk (and don't forget that hyphen), and may also be returning to its old host if I can negotiate with the new style gurus. Or it may be demolished and replaced with something even better, though perhaps not quite so simple to use.

Has the USA started getting the message on CO2 emissions?

Fresh from their willingness to at least "talk about talks" on climate change in Bali, the US Congress has also, for the first time since 1975, moved to significantly beef up the requirements on for more energy efficient vehicles. It aims to reduce America’s dependency on imported oil by raising corporate average fuel economy standards (CAFE) for new cars and trucks to 35 miles per US gallon on average. The 40% increase over the current CAFE standard is intended to cut oil demand by 1.1 million barrels a day by 2020. (The current standards mandate 27.5mpg for cars and 20.7mpg for light trucks. These are equivalent to approximately 33 and 25mpg using the Imperial gallon in the UK, or for cars 8.56l/100km, or 197gCO₂/km. The new CAFE standard is equivalent to 42mpg (UK) or 6.73l/100km or 155gCO₂/km.)

The proposals were part of a wider Energy Bill passed by the senate at the end of last week (13 December). The Energy Bill did however lose two other key environmental elements, one of which would have required utilities to get 15% of their electricity from renewable sources, and the other which would have eliminated huge tax breaks for oil companies. These were removed in response to a likely veto from President Bush.

The Energy Bill also contains a requirement to increase by nearly fivefold US production of renewable motor fuels like ethanol to 83 billion litres by 2022, although this may, as the EnergyDon has noted before, cause more problems than solutions, leading to rising food prices and a potential shortage of corn and soya beans for food uses. (There is also worrying evidence that the US Midwest may run out of irrigation water from underground aquifers, but that's another story...)

Electricity companies in Southern States lobbied strongly against the 15% renewable electricity provision, arguing there are few renewable energy sources like wind in their part of the USA, in contrast to plentiful (and polluting) supplies of cheap coal. No wind along the Gulf Coast – now does that sound right?

While the cut-down energy bill might not be as environmentally benign as its sponsors had hoped, it still represents progress. It is to be hoped that a greener White House in 2008 will allow the change of reintroducing some of the elements lost this year.

Meanwhile the European Commission has confirmed its plans to table draft legislation on this week to reduce CO₂ emissions from new cars, even though the final details of the plan appear to be uncertain. In particular, the Commission may allow car manufacturers to form emissions groups for the purpose of calculating average fleet emissions. This would be similar to a basic form of emissions trading, where producers of larger vehicles could pay the makers of smaller cars to offset their higher emissions.

The European Commission is also expected to try and differentiate between different car classes in meeting the anticipated overall target of 130gCO₂/km by 2012. The calculation will probably be based on three variables, including the weight of the car, in an apparent concession to German manufacturers which manufacture significantly large (and so heavier) cars than the EU average.

So does the new action in the USA mean that it is catching up the European Union, and is this something that we should be pleased about? To answer the second question first, any progress in improving the lamentably bad US fuel economy standards has to be welcomed. However, if they reach 35 miles per US gallon by 2020, they will still be no further forward than we are now, and the EU's proposed standards, while watered down from earlier proposals of 120gCO₂/km, will still be 16% better and 8 years earlier.

But there is another more serious problem. Historically the USA has defended its large, inefficient vehicles by pointing out that their country is large, with a severe climate and long distances. To some extent this has been a self-fulfilling prophecy. US cities suffer from a vast urban sprawl, linked by traffic-clogged freeways, with in most cases few public transport alternatives. If you are sitting in a jam on the Santa Monica freeway in 90° heat, for example, you expect a bit of space in which to stretch and a nicely air-conditioned vehicle. To overcome America's dependency on oil will require more than smaller or more fuel-efficient cars; it will also need a re-think about how America does business and builds itself.