A car changes future net worth through the cash paid upfront, the ongoing costs, any debt and the money left to invest. An owned car also has a remaining value. Follow all of those pieces through the same period to understand the choice.
The question is personal: a car may buy access to work, time with family or a journey you cannot reasonably make another way. The calculation helps put a price on the options you would actually consider.
An eight-year comparison with the same starting household
Here is a fictional household with €40,000 to invest and an existing car worth €8,000. It can allocate €800 a month to transport and saving together. Replacing the car means selling the current one for €8,000; going car-free also releases that money. Keeping it does not create a sale.
Each option lasts eight years. Running costs include fuel or charging, insurance, taxes, servicing, repairs and other transport. Purchases are paid in cash. The numbers below are illustrative inputs, not vehicle quotes or estimates for a particular model.
| Choice | Purchase price | Invested at start | Monthly transport | Monthly investment | Car value at end |
|---|---|---|---|---|---|
| Keep the current car | €0 | €40,000 | €350 | €450 | €2,000 |
| Replace with a used car | €14,000 | €34,000 | €300 | €500 | €7,000 |
| Replace with a new car | €35,000 | €13,000 | €320 | €480 | €16,000 |
| Sell and go car-free | €0 | €48,000 | €180 | €620 | €0 |
Compare investments and the remaining vehicle together
Assume investments earn a constant 4% nominal return after fees and taxes, with deposits at each month’s end. Costs and deposits stay flat in nominal euros. A separate 2% inflation assumption translates the final result into today’s purchasing power. These rates are choices for this example, not Zenarios defaults or return forecasts.
| Choice | Assets at year 8 | In today’s money | Difference from keeping |
|---|---|---|---|
| Keep the current car | €107,405 | €91,669 | €0 |
| Replace with a used car | €109,823 | €93,733 | €2,418 |
| Replace with a new car | €87,831 | €74,963 | -€19,574 |
| Sell and go car-free | €135,493 | €115,642 | €28,088 |
In this example, replacing with the used car finishes slightly ahead of keeping the current one: lower running costs and a higher remaining value offset the extra cash paid. The new car leaves less invested upfront. Going car-free has costs too, but leaves more to invest. Change the repair assumptions, resale values or available alternatives and the comparison can change.
See which part depends on investment returns
| Choice | 0% return | 2% return | 4% return | 6% return |
|---|---|---|---|---|
| Replace with a used car | €3,800 | €3,167 | €2,418 | €1,537 |
| Replace with a new car | -€10,120 | -€14,517 | -€19,574 | -€25,374 |
| Sell and go car-free | €22,320 | €25,042 | €28,088 | €31,491 |
The table does not say a particular return will arrive. It separates the vehicle assumptions from the compounding assumption. It also stops after eight years: projecting the difference to retirement needs an explicit replacement pattern, not the assumption that one car lasts forever.
Use Unterm Strich for the vehicle details
Compare depreciation, financing and running costs in Unterm Strich
. It is a separate tool by the same maker, focused on German vehicle costs and rules. It compares cash purchases, financing, leasing, subscriptions, company cars, keeping a vehicle and alternatives to car ownership.
Its wealth-until-retirement view explores what a monthly difference could grow to. Inspect the investment, tax and inflation assumptions as well as the costs. An amount described as an economic monthly cost is not necessarily the amount leaving your bank every month.
Put the choice into your household plan
In Zenarios, compare the car decision alongside a home purchase, a child, working less and retirement. Enter actual purchase and sale amounts, running costs and financing. Include the vehicle and outstanding debt as assets and liabilities.
Do not add lost investment returns as another bill when the forecast already calculates investment growth. Similarly, avoid charging depreciation as an expense while also reducing the car’s value. Otherwise the same economic cost is counted twice.
Both tools are made by Constantin Metz. They open separately, with no automatic transfer of your numbers. Use Unterm Strich to examine the vehicle choice and the Zenarios car planner to see how that choice fits the rest of life.
Common questions
How do car costs affect future net worth?
Upfront payments and running costs reduce money available to save or invest. An owned car also retains a changing resale value, while financing creates debt and interest. Compare cash flows, remaining assets and debt over the same period rather than treating the purchase price as the only cost.
How are Unterm Strich and Zenarios connected?
They are separate tools by Constantin Metz. Unterm Strich examines vehicle costs and mobility choices with a focus on German costs and rules. Zenarios connects car decisions to a household's income, other goals and retirement. Opening one from the other does not automatically transfer financial data.
Should opportunity costs be entered as a monthly expense?
Do not add forgone investment returns as another cash bill when the forecast already models investments. Enter the actual purchase, sale, running costs and financing, and let the forecast calculate the investment effect. Likewise, avoid charging depreciation as an expense as well as reducing the vehicle's value.
Explore Zenarios
See the Zenarios financial planning features, explore life scenarios and financial decisions, or read about how Zenarios calculates your forecast and how your financial data stays private.
Try Zenarios in your browserWritten by the maker of Zenarios, a software engineer. These guides explain planning concepts and the product; they are not a personalized financial recommendation. Illustrative calculations are not results from your plan.