What are the costs of keeping your money idle?

“I keep my money under the mattress—that’s where it’s safest.” This is a phrase we’ve surely heard our grandparents say more than once. Fear of harder times led them to keep their savings tucked away where they believed it was well protected.

Nowadays, there probably aren’t many people who still stash their cash under the sheets (or maybe there are), but the bad habit of leaving money idle still persists. No longer inside the home, but rather in checking accounts with no interest at all, which generate no return whatsoever. Under these conditions, money doesn’t grow; in fact, it loses value over time.

According to data from the Bank of Spain, a very significant portion of savings is concentrated in demand deposit accounts, which usually offer zero or almost negligible remuneration. What’s more, by the end of 2025, the balance held in these accounts is estimated to have been close to €900 billion.

If this impact is extrapolated to the roughly €900 billion that remains in accounts with little to no remuneration, the loss in the value of savings would exceed €16 billion in just one year. And why does this happen?

This is where inflation comes into play, which is ‘deadly’ for idle money. Put another way, keeping all your money in the bank without investing entails a guaranteed risk: the loss of purchasing power due to rising prices.

The impact of inflation

In recent years, inflation has been high in Spain: it reached 6.5% in 2021 and 5.7% in 2022, before easing to 3.1% in 2023 and 2.8% in 2024. Last year, it continued its downward path to 2.7%.

However, despite this decline, these percentages still erode the value of money. In other words, every euro in the bank is “worth” less as prices rise.

Practical example: What happens to €10,000?

To see more clearly the erosive effect that idle money experiences, let’s look at an example with savings of €10,000 and an average inflation rate of 3%.

• After one year: With 3% inflation, €10,000 would have a purchasing power equivalent to €9,700 after twelve months. This represents a real loss of about €300.
• After three years: Applying 3% annual compound inflation, the initial €10,000 would end up being worth around €9,127, losing about €873 in purchasing power.
• After five years: With the same 3% inflation each year, those €10,000 would end up being worth around €8,587, meaning they would lose about €1,413.

These approximate calculations show that the longer you leave your money inactive, the more inflation eats away at your savings.

Conservative investment alternatives

More conservative profiles may not feel ready to invest in the stock market, but to counter these losses, there are more moderate investment vehicles. These options do not aim for large gains, but they do help preserve purchasing power and allow money to work prudently over the medium and long term.

Among them are interest-bearing accounts and term deposits, which offer a return known from the outset; Treasury bills and high-quality bonds, considered low-risk products that provide periodic income; and money market funds, which invest in very short-term assets and seek stability and liquidity.

In this regard, Mapfre AM has recently launched its first money market fund, Mapfre AM EUROCASH, which offers a return that will depend on the evolution of short-term interest rates in the eurozone. With the six-month Euribor rate at around 2%, the fund presents itself as an alternative to leaving your savings idle, offering daily liquidity, diversification, and security.

It’s important to remember that taking the step toward investing doesn’t mean taking extreme risks or investing all your savings at once. Many people prefer to start gradually, allocating only a portion of their savings while keeping a liquidity cushion.

What is clear is that leaving money idle in the bank comes at a cost: the gradual erosion of purchasing power due to inflation. Being informed and considering conservative investment alternatives is key to protecting your savings. A well-diversified strategy, supported by professional advice and a long-term perspective, will help preserve and grow your wealth.

Need some help?

Getting guidance from financial experts, such as those at Mapfre, can make all the difference. Mapfre Gestión Patrimonial, our specialized financial advisory unit, will help you save and invest for the first time to achieve your financial objectives.