25-year vs 35-year mortgage: which term should you choose?

A 35-year mortgage costs less every month and much more overall. On €300,000 at 4%, a 35-year term costs €1,328.32 a month against €1,583.51 over 25 years — €255 less each month — but you pay €82,843 more interest across the life of the loan (€257,896 versus €175,053). Neither figure is a mistake. They are two different purchases: the long term buys monthly breathing room, the short term buys a lower total cost.

The numbers side by side

Same loan, same rate, three terms. The only thing that changes is how long you take to repay.

Term	Monthly payment	Total interest	Total repaid
25 years	€1,583.51	€175,053	€475,053
30 years	€1,432.25	€215,609	€515,609
35 years	€1,328.32	€257,896	€557,896

Stretching from 25 to 35 years shaves €255 off the monthly payment and adds €82,843 to the interest. The middle option, 30 years, sits close to the centre on both counts.

Why the longer term costs so much more

Interest is charged on the balance you still owe, month after month. A longer term means that balance stays high for longer, so you keep paying interest on a large sum well into the loan’s life. Where compounding grows your savings over time, here it works against you: the slower you clear the principal, the more months of interest pile on top.

This is the mechanics of amortisation. Early in any mortgage, most of each payment goes to interest and only a little to the principal. A 35-year schedule spreads those slow early years even thinner, so the debt barely moves at the start — and every month it sits high is another month of interest charged on it.

The case for each

The short term clears the debt faster and cheaper. You pay €82,843 less interest and own your home outright a decade sooner. If your budget can carry €1,583.51 a month comfortably, the 25-year term is simply the cheaper way to buy the same house.

The long term lowers the payment you are committed to. That €255 a month of room can be the difference between a mortgage a lender will approve and one it won’t — because the borrowing rules assess your repayment capacity, and a smaller required payment is easier to pass. In a stretched budget, or when rates and living costs are high, the lower fixed commitment buys security.

The honest framing: the 25-year term is cheaper if you can afford it, and the 35-year term is safer if money is tight. Both are rational. They answer different questions.

The middle path most people miss

You do not have to choose the low payment and accept the high cost. Take the longer term for the safety of a smaller required payment, then overpay when you can. Every overpayment goes straight at the principal, which quietly shortens the term month by month.

The effect is large. On €300,000 at 4% over 30 years, overpaying €100 a month saves €28,747 in interest and clears the loan 3 years 6 months early — paid off in 26 years 6 months. Overpaying €200 a month saves €50,412 and finishes 6 years 2 months early, in 23 years 10 months.

This gives you the best of both: the low committed payment protects you in a hard month, and the overpayments — made only when you can spare them — pull the total cost back down toward what a shorter term would have cost. Check your mortgage allows penalty-free overpayments first, as terms vary between lenders.

One honest caveat

A longer term usually means paying into later life. A 35-year mortgage taken in your forties runs past a normal retirement age, and lenders set a maximum age by which the loan must be fully repaid. That ceiling can rule the long term out entirely, or cap how long a term you are offered. Before you plan around a 35-year mortgage, confirm the lender will actually lend over that term at your age — because a personal decision this large is one a qualified adviser should weigh with you.