For years, the FIRE movement has attracted people with a simple but powerful promise: save aggressively, invest consistently and retire decades earlier than the traditional retirement age.

The concept, known as Financial Independence, Retire Early (FIRE), gained popularity in the United States as high-income earners shared stories of leaving the workforce in their 30s and 40s. Through a combination of extreme saving, disciplined investing and relatively low living expenses, some were able to accumulate enough wealth to support themselves indefinitely.

However, the formula does not always translate easily to Spain, as many face a different economic reality. Salaries are generally lower than those in the United States, taxes reduce take-home pay and housing costs have risen sharply in many parts of the country. For workers earning average incomes, the prospect of retiring at 40 can feel impossible to reach.

That said, there’s still a way to make FIRE work that is less aggressive than traditional methods— it’s known as Coast FIRE, and it’s never too late to start.

Rather than focusing on leaving work altogether, Coast FIRE aims to build enough wealth early in life so that retirement savings can continue growing on their own. Once that milestone is reached, investors can stop prioritizing aggressive retirement contributions and instead focus on covering their current living expenses.

For many in Spain, that may be a more achievable path to financial independence.

What is Coast FIRE and how does it work?

The idea behind Coast FIRE is quite simple: an investor reaches Coast FIRE when their investment portfolio becomes large enough that, assuming reasonable long-term market returns, it should grow into a fully funded retirement nest egg without requiring additional contributions.

Calculate your FIRE number here.

In practical terms, that means someone who reaches their Coast FIRE number at age 35 or 40 may no longer need to dedicate a large percentage of their salary toward retirement savings. Instead, they can allow time and compound growth to do most of the remaining work.

Imagine a 35-year-old investor who has accumulated €150,000 in broadly diversified investments. If those investments grow at an average annual rate of 7% over the next 30 years, the portfolio could potentially exceed €1 million by age 65 without a single additional contribution.

The exact numbers depend on market performance, inflation and retirement goals, but the principle remains the same: save aggressively early, then let compound growth carry the portfolio toward retirement.

Unlike traditional FIRE, however, reaching Coast FIRE does not mean leaving the workforce. Most people continue working. The difference is that they gain flexibility. They may switch to a less stressful job, reduce working hours, launch a business or pursue work that offers more personal satisfaction rather than the highest possible salary.

Why Coast FIRE may be more realistic for Spanish workers

The FIRE movement was largely built around income levels that are difficult for many Spanish households to replicate. Many of the earliest success stories came from software engineers, finance professionals and entrepreneurs earning six-figure salaries, where saving 50% or more of income was challenging but feasible, which is not the case in Spain.

Housing costs in cities such as Madrid, Barcelona, Valencia and Málaga have risen sharply in recent years, while everyday expenses continue to compete with retirement savings for a share of household budgets. For someone earning €35,000 annually, setting aside half their income is considerably harder than it is for a professional earning €150,000.

On the flip side, Spain’s social safety net such as public healthcare reduces one of the major retirement risks faced by, say, Americans, while the state pension system can provide a foundation of retirement income that many FIRE calculations elsewhere do not assume.

Coast FIRE vs. traditional FIRE: What's the difference?

Although both approaches fall under the broader FIRE umbrella, their goals are significantly different.

Traditional FIRE often requires investors to save 50% or more of their income for years while building a portfolio large enough to support all future living expenses. Coast FIRE lowers that hurdle considerably.

Instead of attempting to fund an entire early retirement, investors only need enough invested assets to reach traditional retirement age through long-term market growth. That distinction may seem small, but it changes the entire strategy.

Rather than asking, "How quickly can I stop working?" Coast FIRE asks, "How quickly can I stop worrying about retirement savings?"

Unexpected risks that could derail a Coast FIRE plan

Like any long-term financial strategy, Coast FIRE depends on assumptions that may not always hold true.

Market returns may fall short

Many Coast FIRE projections assume annual investment returns that average between 6% and 8% over decades. While historical market performance supports those assumptions, future returns are never guaranteed. A prolonged period of weak growth could leave investors with smaller portfolios than expected.

Inflation can change the numbers

Inflation remains one of the biggest threats to long-term financial planning. A retirement lifestyle that appears affordable today may require significantly more income 20 or 30 years from now. Underestimating future inflation can create a substantial gap between projected and actual retirement needs.

Housing costs are difficult to predict

Housing represents one of the largest expenses for most households. Rent increases, property taxes, maintenance costs and homeowners' association fees can all rise faster than anticipated. Investors who underestimate future housing costs may find their Coast FIRE calculations overly optimistic.

Life doesn't always follow the spreadsheet

Marriage, divorce, children, caregiving responsibilities, career changes and health issues can dramatically alter financial plans.

The spreadsheets used to calculate Coast FIRE rarely account for every major life event. That does not mean the strategy is flawed. It simply means investors should build flexibility into their assumptions and revisit their plans regularly.

Reality check

In order to retire at 40, it requires an unusual combination of high income, disciplined saving and favorable market returns. While it is certainly possible for some households, it is unlikely to become a mainstream retirement strategy.

Coast FIRE offers a different approach, where instead of pursuing complete financial independence as quickly as possible, it focuses on reaching a point where retirement is effectively on autopilot. The reward is not necessarily early retirement, but the freedom to make career and lifestyle decisions without constantly worrying about whether enough is being saved for the future.

In a country where average salaries often make traditional FIRE difficult to achieve, that kind of flexibility may prove far more valuable—and far more realistic—than retiring decades early.