Carbon payback calculator

How carbon payback works

A car has two kinds of carbon footprint. There is operating carbon, the emissions from driving it: burning petrol or diesel for one car, and generating the electricity for an EV. And there is embodied carbon, the one-off emissions from building it, which for an electric car is dominated by the battery.

Your current car is already built, so its embodied carbon is spent and gone. Going electric means you avoid most of the operating carbon, but a new EV adds a fresh embodied-carbon debt. The payback period is how long the lower running emissions take to cancel out that debt. After that point, the EV is cleaner for every mile.

Why a used EV pays back almost instantly

When you buy a used EV, the carbon to build it was already emitted by the first owner. Your purchase does not create that footprint a second time, so there is barely any embodied carbon to pay back. From the first mile, a used EV is cleaner than keeping a petrol or diesel car. This is why a used EV is often the greenest option of all.

Why this can take longer than the figures you may have seen

You may have read that an EV pays back its extra carbon in around two years, or 20,000 to 30,000 miles. That figure compares building a new EV against building a new petrol car, where only the battery makes the difference. This tool asks a harder question: keep the car you already own, which carries no new manufacturing carbon at all, or build a brand-new EV from scratch. Measured that way the EV has to repay its whole build footprint, not just the battery, so the payback is longer. That is the fair comparison when your alternative is simply keeping your current car. Buying a used EV sidesteps this entirely, because that car is already built.

Why we add upstream emissions to petrol and diesel

Burning a litre of petrol is not the whole story. Extracting, refining and distributing that fuel produces carbon before it ever reaches your tank. We add this well-to-tank uplift so petrol and diesel are compared fairly against grid electricity, which is itself measured on a generation basis.

Our manufacturing-carbon figures

We estimate the carbon to build an EV from a vehicle baseline plus the battery, sized from your chosen battery capacity. Battery manufacturing is the biggest single factor and the most uncertain, so we use a mid-range value and show the sensitivity in the tool. These figures draw on published lifecycle analysis from the International Council on Clean Transportation (ICCT).

The UK grid is getting cleaner

The carbon intensity of UK electricity has fallen sharply over the last decade and continues to drop as more wind and solar come online. The calculator uses a current average, but because the grid keeps decarbonising, a real EV will usually beat the figures shown here over its life. Want the cost side too? Try the EV Savings Calculator.