One Car vs Two: Should You Replace Both?

Use this calculator to find out whether replacing your two existing cars with a single new car would save you money. Enter your two current cars and their mileage split, then enter the new replacement car — which would cover all the miles on its own.

One Car vs Two Cars
Purchase price minus what you'd get for selling both existing cars. Used to calculate the payback period.
Existing Car 1
Existing Car 2
New Replacement Car

Enter your figures above and click Calculate to see your result.

How the One Car vs Two Comparison Works

This calculator compares the combined annual cost of your two existing cars against the cost of running a single new replacement car that covers all the same miles. Each existing car has its own fuel type, MPG, fixed costs (insurance, tax, depreciation) and a share of the total annual mileage you enter.

The replacement car is treated as covering 100% of the miles on its own. The calculator then shows whether the change saves money each year — and if you provide a net purchase price (the replacement's price minus what you'd get for selling both existing cars), it also shows the payback period in years.

When Replacing Two Cars With One Makes Sense

Consolidating to a single car typically pays off when:

  • One of the existing cars sits unused most of the week, but still incurs full insurance, road tax and depreciation.
  • Both existing cars are old and inefficient, and the replacement is a modern hybrid or EV with much lower running costs.
  • You no longer need two cars in different roles — for example, after a job change or a child leaving home.

It rarely pays off when each existing car has a distinct, high-utilisation role (e.g. a tradesman's van plus a family car), or when both cars are already cheap to run.

Frequently Asked Questions

It can make sense when the two existing cars are old, expensive to insure or inefficient, and a single newer or more efficient car could cover all the mileage at lower total cost. It's particularly worth considering if one car sits idle most of the time.

Enter the total annual miles and what percentage each existing car covers. The replacement car is assumed to cover all the miles on its own. Fixed costs (insurance, road tax) apply to all cars; fuel and variable depreciation scale with each car's mileage share.

The calculator compares total annual costs including fuel, road tax, insurance, servicing and repairs, and depreciation. The combined cost of the two existing cars is shown alongside the cost of running the single replacement car.