When Refinancing Is Worth It: The Break-Even Calculation
There is one calculation and it takes two minutes. Add up everything switching costs. Divide by the monthly saving. That is the number of months you must stay for the switch to be worth doing.
Everything else — rate speculation, lender loyalty, the feeling that you ought to be doing something — is noise around that fraction.
The break-even sum#
Total cost of switching, divided by monthly saving, equals the break-even in months. If you will plausibly still hold the mortgage well past that point, refinance. If not, do not.
| Item | Example |
|---|---|
| Early repayment charge on the current loan | 1,800 |
| New arrangement fee | 995 |
| Valuation and legal | 400 |
| Total cost | 3,195 |
| Current payment | 1,420 |
| New payment | 1,255 |
| Monthly saving | 165 |
| Break-even | About 20 months |
Twenty months is a reasonable switch if you intend to stay for five years and a poor one if you are selling next summer. That is the whole decision.
The four cases where refinancing usually pays#
- Your fixed period is ending. The reversion rate is normally much higher, the early repayment charge has expired, and doing nothing is the expensive option.
- Your LTV has crossed a band. Payments plus price growth may have moved you from 85 per cent to below 80, which is a genuinely better rate band on the whole balance.
- Rates have fallen materially since you fixed and the exit charge is small or gone.
- Your circumstances have improved — debt cleared, income evidenced differently, a poor credit event now old enough to have dropped off.
The second case is the one people never check. Ask for a valuation or check comparable sales before assuming your LTV is what it was at purchase.
The four cases where it usually does not#
- A large early repayment charge with a short remaining fix. Wait for the charge to fall or expire; it usually steps down annually.
- You plan to move within the break-even period. Ask about porting instead.
- Your circumstances have worsened — a job change, new self-employment, a debt taken on. A refinance is a full new application and can be declined.
- The saving is small and you are extending the term to produce it. That is not a saving, it is a deferral with interest attached.
The last case deserves care. Refinancing to a new twenty-five-year term at a lower rate can reduce the payment and increase the total cost. Compare total cost, not the monthly figure.
Refinancing to release equity#
Borrowing more against the property to fund something else — a renovation, consolidating debt, a large purchase — is a separate decision that happens to use the same mechanism. It converts short-term debt into secured, long-term debt, which lowers the interest rate and lengthens the payment period dramatically.
- Consolidating a five-year loan into a twenty-year mortgage can cost more in total despite the lower rate.
- The debt becomes secured on your home, which changes the consequence of not paying it.
- Renovation borrowing can be sound where it adds value or is unavoidable; check whether the property will support the new LTV.
- Releasing equity reduces your equity buffer, which matters if prices fall.
The lower rate is real and the longer term is also real. Run both totals before deciding, and be honest about whether the underlying spending habit is also being addressed.
The process, and how long it takes#
- Start three to six months before your fixed period ends — offers are usually valid for months, so an early offer costs nothing.
- Get your current lender’s retention offer first; it is often competitive and requires almost no paperwork.
- Compare it against the open market on total cost over the new fixed period, including fees.
- Check your current LTV, because it may have improved and moved you into a better band.
- Apply, expecting a full assessment: income, commitments and a valuation.
- Complete before the reversion rate starts, not after.
Step two is worth doing properly. A retention offer avoids legal work and valuation entirely, and the convenience is worth something real — but it is a starting point rather than a final answer.
Frequently asked questions
When is it worth refinancing a mortgage?
When the total cost of switching divided by the monthly saving gives a break-even period comfortably shorter than the time you will keep the mortgage. Add the early repayment charge, the new arrangement fee, valuation and legal costs; divide by the saving. Twenty months is fine if you are staying five years and poor if you are selling next year. The strongest case is the end of a fixed period, when the exit charge has expired and doing nothing means moving to a much higher reversion rate.
Does refinancing hurt my credit score?
It causes a temporary dip and is not a lasting problem. A refinance is a full new mortgage application, so it involves a hard credit search and, briefly, a new account alongside the old one. Both effects fade within months. What does matter is timing: avoid applying for other credit in the same period, since several applications in a short window look worse than one.
Should I refinance to consolidate other debts?
Sometimes, and carefully. Moving a personal loan onto a mortgage cuts the interest rate but stretches the repayment over twenty years or more, so the total paid can rise even at the lower rate — and the debt becomes secured on your home, which changes what happens if you cannot pay. It can be the right decision when the alternative is expensive short-term credit, provided you compare total cost rather than monthly payment and address whatever produced the debt.
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