Used Electric Car Battery Health Now Sets the Price You Pay

For years, the first number a used car buyer looked at was the mileage on the clock. For a used electric car in 2026, there is a more important figure, and many buyers still do not ask for it. Battery State of Health, usually shortened to SOH, has quietly become the single biggest factor in what a second hand EV is worth. Two identical cars of the same age and mileage can now carry very different price tags purely because one battery has aged better than the other. With used electric cars selling in record numbers, knowing how to read and check that figure is the difference between a smart buy and an expensive mistake.

What State of Health actually measures

State of Health is a percentage that describes how much of a battery’s original capacity remains. A pack at 100 per cent holds as much energy as it did when the car left the factory. At 90 per cent it holds nine tenths of that, which translates into roughly nine tenths of the original range. It is not the same as the charge level on the dashboard, which simply tells you how full the battery is right now. SOH is about the long term health of the pack, and unlike a petrol engine it declines gradually and predictably rather than failing overnight.

The reassuring news for buyers is that modern batteries are lasting far better than the early scare stories suggested. A large UK study found used electric cars were holding around 95 per cent of their battery health on average, a finding we covered in our report on why your EV battery is probably healthier than you think. The industry generally treats a pack as having reached the end of its useful automotive life only once SOH falls below 70 per cent, and most cars on the used market are nowhere near that.

Why battery health now drives the price

The used EV market has grown up fast. More than 274,000 used battery electric cars changed hands in the UK during 2025, up almost 46 per cent on the year before, and demand has only climbed as pump prices stayed high, a trend we tracked in our piece on record used EV sales. As volumes have risen, the trade has shifted from guessing at battery condition to measuring it, and SOH has become the metric that sets the figure on the windscreen.

The pricing data shows why it matters to your wallet. Figures from Cox Automotive and Cap HPI put average electric car depreciation at around 38 to 42 per cent after three years, against roughly 35 to 40 per cent for an equivalent petrol model, and the AA has noted used EVs trading about 10 per cent cheaper than comparable combustion cars. Within that, a car with a verified 90 per cent or higher SOH commands a clear premium over one sitting in the mid 70s, even if the age and mileage are identical. Heavy discounting of brand new EVs to meet sales targets has also pulled down used values, which makes a strong, provable battery figure all the more valuable to a seller.

How to check a used EV’s battery health

As of early 2026 there is still no UK law forcing a seller to provide a battery health certificate on a private sale, so the responsibility to check falls on the buyer. There are four reliable routes, and it is worth using more than one.

• The car’s own menu. Many modern EVs, including Teslas, Polestars and recent BMWs, carry a battery health readout in the infotainment system. It is a useful first indication, though a phone snap of the screen is treated as informal rather than proof.
• An independent OBD test. Third party services such as Aviloo plug a device into the car’s diagnostic port and produce a certified PDF report. Independent certification carries far more weight than a dashboard figure because it cannot be cherry picked.
• A main dealer diagnostic. A franchised dealer for the car’s brand can run a battery health check, often as part of a service, and put the result in writing.
• An approved used certificate. Several manufacturer approved used schemes, including those from Volvo, Polestar and Hyundai, now include a battery health certificate as standard, and dedicated certification services are expanding across the trade.

Whichever route you choose, also ask to see the manufacturer’s battery warranty paperwork. Most makers guarantee the pack will stay above a set capacity, commonly 70 per cent, for a number of years or a mileage limit, and a car still inside that warranty gives you a valuable safety net.

What counts as a good number

Context is everything, because some battery loss in the first months is normal before the rate of decline settles. As a rough guide, a five year old EV in good condition commonly retains somewhere between the mid 80s and around 90 per cent of its original capacity. Anything in the 90s is excellent, the 80s is healthy and ordinary, and a figure drifting towards the low 70s deserves a hard look at the price and the warranty. Compare the SOH against the car’s age and mileage rather than judging it in isolation, and be wary of a pack that has aged unusually fast, which can point to heavy rapid charging or hard use.

What it means if you are the one selling

The same shift works in your favour when it is time to sell. A strong, independently verified battery figure is now one of the most persuasive things you can put in an advert, and it can lift the price a cautious buyer is willing to pay. Paying for a certificate before you list removes the buyer’s biggest worry and can pay for itself many times over. Look after the pack in the meantime by leaning on slower home charging rather than constant rapid charging, and by avoiding sitting at very high or very low charge for long periods, advice that holds whether you plan to keep the car or move it on. With good cars of every kind in short supply, as we set out in our report on the used car crunch, a healthy battery you can prove on paper is fast becoming the most bankable asset an electric car can have.

The questions to ask before you buy

A few direct questions at the viewing will tell you most of what you need to know. Ask how the car has usually been charged, because a vehicle topped up mainly on a home wallbox overnight tends to age more kindly than one that has lived on motorway rapid chargers. Ask whether the seller can produce a recent battery health report rather than just a dashboard reading, and treat reluctance as a reason to keep looking. Ask to see the service history and confirm any software updates have been applied, since manufacturers occasionally improve battery management through updates that protect the pack over time. Finally, ask how much of the battery warranty remains and whether it transfers to you, which on most cars it does as long as servicing has been kept up.

It also pays to separate fact from fear. A battery losing a few per cent of capacity over its first year or two is entirely normal and not a sign of a fault, and a car that has covered a high mileage is not automatically a poor bet if its SOH has held up. The reverse is true as well: a low mileage car that has been left at full charge in a hot garage for years can show more wear than the odometer suggests. Judge the pack on its measured health, the warranty position and how it has been treated, and the headline mileage becomes just one part of a fuller picture. Spend a little time and, where the price justifies it, a little money on an independent check, and you turn the most daunting part of buying an electric car into the most reassuring.

Sources:

• https://www.carwow.co.uk/news/10307/used-ev-battery-health-study-uk
• https://www.parkers.co.uk/car-news/electric/used-car-battery-health-certificates/
• https://www.fleetnews.co.uk/news/battery-health-certification-for-used-evs-launched-by-ayvens