The Driveway Spare: Adding Up the Petrol Car You Keep 'Just in Case'

The car that never quite leaves

Almost every EV household knows the conversation. The main car is electric, the commute is cheap, the school run is silent, and then someone says: “But what about the drive to Scotland?” Cue the small petrol hatchback on the driveway, taxed, insured and MOT’d, ostensibly there for the long trips, the tip runs and the odd week when the charger is out of action.

It sounds sensible. It often is not cheap. A spare car is not a spare tyre. It has its own paperwork, its own wear items and its own steady slide in value, even if it barely turns a wheel. If you are keeping a petrol stand-in “just in case” in 2026, it is worth adding up what that case is actually costing.

The bills that arrive whether you drive it or not

Start with the fixed costs. A standard petrol car will generally face VED around the £195–£220 mark depending on its registration date and emissions band. Insurance for a low-mileage second car might be £350–£600, though multi-car policies and limited-mileage cover can bring that down. An MOT is capped at £54.85 for a car, and even a gentle service tends to land somewhere between £200 and £400 once oil, filters and a look underneath are included.

Then there is depreciation. This is the quiet one. A £6,000 used petrol runabout might lose £700–£1,200 a year in value if it is sitting outside ageing gracefully. A newer spare could lose far more. Add a contingency for tyres, brakes, a battery that dislikes inactivity and the occasional suspension knock, and £250–£500 is not pessimistic.

Fuel is the only genuinely variable line. If the car does 2,000 miles a year at 45mpg and petrol sits around £1.40 a litre, you are looking at roughly £280. Total it up and a modest second petrol car can easily cost £2,000–£3,000 a year before anything dramatic happens. That is not a disaster. It is simply a number that deserves to be compared with the alternatives.

What the alternatives actually cost

A weekend hire car is often £80–£150 for a small hatchback, more in peak season and more again if you need an estate or something with a tow bar. A car club can work out cheaper for short bursts, especially if you only need a car for a few hours, but availability varies sharply by postcode and the best deals rarely cover every need.

Public rapid charging is the other alternative to keeping petrol for long trips. Yes, it costs more than charging at home. Yes, reliability and queueing can be annoying. But a handful of rapid-charging stops a year is unlikely to cost £2,500. For many drivers, the real cost of charger anxiety is a little planning, not a second car.

Towing is the exception. If you genuinely need a petrol tow car for a caravan, horsebox or trailer, hiring is not always straightforward and the EV alternatives may not suit your licence, budget or route. That is a legitimate reason to keep a suitable car. “We might go to the Lake District once” is not.

The break-even test

Here is a simple way to decide. Add up the annual fixed and likely running costs of the spare: VED, insurance, MOT, servicing, depreciation, repairs and fuel. Then divide that total by the typical cost of hiring a car for the trips you would otherwise take.

If the spare costs £2,400 a year and a weekend hire costs £120, you need about 20 hired weekends to break even. Be honest: did you use the petrol car 20 times last year for journeys a hire car could have covered? If not, the spare is not a safety net. It is a subscription to having another car on the drive.

There is a second test too. Count the occasions when the petrol car saved a journey that public charging, a hire car or a car club could not reasonably have handled. If that number is in single figures, the case is weak. If it is high because of work, caring duties or towing, the maths may look very different.

Where the spare still earns its keep

There are households where the second petrol car makes genuine sense. A rural household with poor public transport, no driveway charging and a regular need for long, unscheduled journeys may find the flexibility worth the bill. A family that tows, or one with a driver who cannot easily use public rapid chargers, may also justify it. And a very cheap, reliable older car that is used often enough can be cheaper than repeated hiring.

The trap is letting the spare become an ornament with a direct debit. If it is only there because changing habits feels awkward, try a trial separation. SORN it if it is off the road, or sell it and bank the savings for hire cars and rapid charging. After three months, you will know whether you miss the car or just the idea of it.

The honest ledger

A petrol safety net is not irrational. It is just a financial decision wearing a comfort blanket. Run the numbers for your own household, including the boring bits like insurance renewals and the MOT you forgot was due. If the spare car is used enough, keep it with a clear conscience. If it is not, the most eco-friendly and wallet-friendly move may be to stop paying for reassurance you are not actually using.