A provocative new study says replacing even a nearly new petrol car with an EV can reduce carbon emissions. The maths is credible, but real cars, real owners and the global motor industry make the answer more complicated
Imagine you own a perfectly good petrol car. It works, it is reliable and it might be only a year or two old. According to a startling new scientific study, the environmentally responsible thing could be to scrap it and buy a brand-new electric car. Yes, really. New Scientist summed up the finding with the wonderfully provocative headline: “It’s good for the planet to scrap a new petrol car and buy electric.”
Your first reaction may be the same as mine. Come on! How can destroying a working machine, mining more materials, manufacturing a large battery, building another car and potentially shipping it halfway around the world possibly be greener?
Well, the underlying research suggests the carbon saved by driving an electric car is usually substantial enough to outweigh the emissions created by manufacturing it.
That is fascinating. Within the boundaries of the study, it may well be right. But does it mean we should all rush outside, wave farewell to our faithful petrol cars and send them to the crusher?
This is where the neat scientific model meets the magnificently untidy real world.
What does the study actually claim?
The research was conducted by J. Elliott Campbell of the University of California, Santa Cruz and Roland Geyer of UC Santa Barbara. Their paper, “The climate benefits of retiring a fully operational internal combustion engine vehicle”, was published in the journal Science.
The researchers compared two possible futures for the same driver. In the first scenario, the owner keeps an existing petrol car for its expected useful life, assumed to be around 16 years. In the second, the working combustion car is retired early and replaced with a battery-electric vehicle.
This is a proper lifecycle comparison. The calculations consider considerably more than exhaust emissions. They include producing the petrol, generating electricity, manufacturing the EV and its battery, operating both vehicles and eventually retiring them.
According to the university’s summary, replacing the average petrol vehicle during its first year resulted in a 58 per cent reduction in carbon emissions over the 16-year period.
The additional emissions produced while manufacturing the EV were typically recovered after approximately three years of driving.
Across the different combinations examined, 92 per cent of scenarios involving the early replacement of petrol or conventional hybrid vehicles delivered at least some reduction in overall carbon emissions. Those are significant numbers.
Why the basic argument is credible
The manufacturing emissions from your existing car have already occurred. Economists call that a sunk cost, which is a slightly cold way of saying the car has already committed its original environmental sins. You cannot unbuild it. From today onwards, the relevant question is how many additional emissions that car will produce.
Every mile driven in a petrol or diesel car requires more fuel. Oil must be extracted, transported, refined and distributed before reaching the filling station. The engine then burns it, producing fresh carbon dioxide.
Combustion engines also throw away a remarkable amount of their energy as heat. According to US government efficiency estimates, only around 20 to 30 per cent of the energy stored in petrol typically reaches the wheels.
Diesel engines usually do slightly better, while conventional hybrids improve efficiency through regenerative braking, reduced idling and cleverer use of the combustion engine.
A battery EV can deliver roughly 80 to 90 per cent of the energy stored in its battery to the wheels. Even after allowing for charging losses, the efficiency advantage remains substantial.
An EV normally begins life with a larger manufacturing footprint, primarily because of its battery. Once it enters service, however, it uses energy far more efficiently and produces no carbon dioxide from a tailpipe. There is, of course, no tailpipe.
If the vehicle covers a lot of miles and charges from a reasonably clean electricity supply, the avoided petrol emissions can overtake that initial manufacturing penalty surprisingly quickly.
The argument becomes particularly compelling for taxis, buses, delivery vans, ride-hailing vehicles and company fleets. These vehicles cover huge distances and consume large quantities of fuel, so every battery deployed in one can displace a serious amount of daily petrol or diesel use.
For those applications, electrification makes enormous sense.
The crucial question: what happens to the old car?
The strongest version of the study’s result depends on the combustion car genuinely leaving active use.
That may happen through a properly administered scrappage programme. In ordinary private-car ownership, however, most people will not send a one or two-year-old car to the crusher. They will trade it in.
It will appear on a used-car forecourt, move into another household, become a second family car or be exported to another country. It could continue burning petrol for another decade.
The original owner’s personal emissions may fall after buying an EV, but the old car is still being driven elsewhere. At a global level, some of those emissions have merely changed owners or crossed a border.
A flood of relatively cheap combustion cars onto the used market could produce other effects too. Somebody who previously relied on public transport might decide to buy one. A household could add an extra vehicle instead of replacing its current car.
This is why “retired” has to mean genuinely removed from active use, properly dismantled and responsibly recycled.
The figure of 92 per cent also needs context. It refers to 92 per cent of the combinations modelled by the researchers. It does not mean that replacing 92 per cent of every petrol, diesel and hybrid car in the real world would automatically deliver the same result.
“Good for the planet” is a very broad claim
The study provides a greenhouse-gas assessment within a defined model. That is valuable, but “good for the planet” encompasses a much wider environmental picture.
Electric cars require mining, mineral processing, battery production, vehicle assembly, global transportation and charging infrastructure.
Those activities consume energy and materials. They can affect water supplies, habitats, local air quality and communities around extraction and processing sites.
Shipping a car or its components across the world may account for only a modest proportion of its total lifetime footprint, particularly if the vehicle is heavily used. It still counts.
Vehicle size matters as well. Replace a thirsty petrol SUV with an efficient electric hatchback and the environmental case looks strong.
Replace a lightly used petrol supermini with a huge electric SUV carrying a 100kWh battery and the calculation becomes rather less flattering.
A larger battery requires more material and generally produces more manufacturing emissions. It also adds weight, which increases energy consumption and tyre wear.
Matching the replacement to the driver’s actual needs should be part of any sensible transition.
Some drivers may gain very little from switching early
The researchers acknowledge several important exceptions.
The case becomes weaker for cars covering very low annual mileages, efficient plug-in hybrids and vehicles charged from electricity grids that depend heavily on coal.
The study’s approximate break-even mileage is around 7,000km per year for cars and SUVs, equivalent to roughly 4,350 miles. Pickup trucks require a somewhat higher annual mileage.
Plenty of privately owned cars cover less than that.
If an efficient petrol car is driven only occasionally, replacing it immediately may deliver a relatively small carbon benefit. Depending on the replacement vehicle, electricity source and battery size, allowing the existing car to complete more of its useful life could remain perfectly reasonable.
What if the whole world switched at once?
There are approximately 1.7 billion cars in the world.
Clearly, nobody could replace the entire global combustion fleet overnight. Using it as a thought experiment, however, exposes the limitations of scaling an individual-driver result into universal policy.
Imagine trying to scrap one billion functioning petrol and diesel cars and replace them with one billion EVs in a short period.
Mining and refining would surge. The world would require more battery factories, more steel, more aluminium, more vehicle assembly capacity, more cargo ships, more power generation and a vast expansion of charging infrastructure.
It would also need enough recycling capacity to process mountains of prematurely discarded cars.
Assume, purely as back-of-the-envelope maths, that manufacturing each replacement EV produced eight tonnes of carbon-dioxide equivalent. One billion cars would create an immediate manufacturing pulse of eight billion tonnes.
Lower operating emissions might repay that enormous upfront hit over time. How quickly would depend on vehicle mileage, battery size, manufacturing methods, electricity generation and how long the EVs remained in service.
The rush itself would also change the market. Fuel prices, electricity demand, mineral costs, factory construction, consumer behaviour and patterns of vehicle ownership would all react.
A calculation that works for one driver cannot simply be multiplied across a billion motorists without accounting for those systemic effects.
A practical route to electrification
The transition should begin with vehicles that burn the most fuel and travel the greatest distances.
Taxis, buses, delivery vehicles, ride-hailing cars and business fleets should be high priorities. Each EV introduced into these roles can replace a large quantity of daily fuel consumption.
Next should come older and inefficient privately owned vehicles approaching the natural end of their useful lives. At that point, the outgoing car can genuinely be retired and recycled.
The replacement should also be appropriately sized.
A small petrol hatchback does not need to be succeeded by a massive electric crossover. Smaller and lighter EVs require fewer materials, consume less energy and can use more modest battery packs.
We also need to clean up the electricity grid and the energy used by battery and vehicle factories.
An electric car’s operating footprint can improve during its life as the grid becomes cleaner. Build its battery using lower-carbon electricity from the beginning and it starts life with a smaller environmental debt.
Battery recycling capacity must expand before the first enormous wave of EV packs reaches retirement. Recovering lithium, nickel, cobalt, copper and other materials will reduce the pressure to extract fresh resources.
Scrappage schemes should therefore be targeted rather than indiscriminate. They should prioritise:
• High-mileage vehicles
• Cars with high fuel consumption
• Areas with cleaner electricity
• Smaller and more efficient replacement EVs
• Verified permanent retirement of the outgoing vehicle
Put each new battery where it delivers the greatest possible reduction in fuel use.
Should you scrap your petrol car?
The study is built around a genuine and important insight.
Manufacturing an electric car creates a sizeable initial burst of emissions. Burning petrol creates new emissions every time the existing car is driven.
If a vehicle works hard and covers a lot of miles, replacing it with an EV can overcome the manufacturing penalty much sooner than many people expect.
That makes a strong case for replacing high-mileage combustion vehicles.
It becomes much shakier as general advice for every owner of every functioning car.
Most private cars spend much of their lives parked. Some cover remarkably few miles. Scrapping them prematurely could create unnecessary material demand while delivering only a modest reduction in operating emissions.
The most environmentally sensible answer depends on several questions:
- How far do you drive?
- How efficient is your existing car?
- What type of EV would replace it?
- Where and how would the EV and its battery be manufactured?
- How clean is the electricity used to charge it?
- What would actually happen to your old car?
Electrification remains one of the most powerful tools available for reducing transport emissions. A sensible transition should replace the worst polluters in the busiest locations, encourage appropriately sized EVs, clean up manufacturing and electricity supplies, and allow lightly used, efficient vehicles a sensible working life.
So, should you scrap your perfectly good petrol car and buy an EV right now?
The honest answer is: it depends how you do it.
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Excellent analysis — the ‘matching the replacement to the driver’s actual needs’ point is the one that gets lost in the headlines. The study’s 7,000km break-even means a low-mileage second car gains almost nothing from an early switch, and a 100kWh SUV changes the whole equation versus a small efficient EV. For anyone weighing the switch, the practical move is to shortlist the right car for your actual mileage first — DrivePedia’s car finder (https://drivepedia.site/tools/finder) matches three cars to your real needs in about a minute. Right-sized replacement first, scrappage decision second.