Regular saving or a lump sum: compare the money actually available
How much of the difference comes purely from payment timing?
Regular saving from income and investing money already available serve different purposes. A higher final value from an early lump sum does not prove that monthly saving is a poor decision. What matters is which money is actually available at each point in time.
Time in the model makes the difference
Earlier contributions can earn returns for longer. Monthly payments arrive gradually; the final payment has little or no time to grow. A comparison must disclose the contribution total, payment dates and end date. Otherwise, a larger final value may simply reflect more capital or capital available earlier.
Equal totals, different investment time
Illustrative assumptions: €200 at each month-end for five years, a nominal 3% annual rate credited monthly, without fees or tax. Contributions total €12,000; the final value is €12,929.34. Investing €12,000 at the start under the same conditions produces €13,939.40. Here, the €1,010.06 difference comes entirely from the payment dates.
Existing capital is not future income
Someone who earns the €200 each month cannot invest the entire five-year amount today. If the money is already available but is to be invested gradually, the uninvested balance must also appear in the comparison: where is it held, what return does it earn, and is a reserve left untouched?
A constant model rate is not a stock-market path
The example uses a constant calculation rate. With fluctuating asset prices, actual purchase dates change the outcome. Regular purchases spread entry dates but guarantee neither a profit nor an advantage over a lump sum. Per-order fees can weigh more heavily on small contributions; an assumed average rate does not fully represent this payment pattern.
Work backwards from a savings goal
Set the target date and required amount. Separate the existing lump sum from the affordable monthly contribution and calculate several return assumptions. Also test a zero-return case. If the goal is a particular purchasing power, price changes must be included. The savings calculator combines these inputs; it does not choose a financial product for you. The Bundesbank distinguishes nominal interest from inflation-adjusted real interest; keeping them separate prevents equating an amount of money with its purchasing power.
A fair comparison starts with availability of the money. Equal contribution totals produce different final values at different payment dates; that alone does not establish a universal product recommendation.