Ask ten homeowners how much they saved by refinancing and you’ll get ten different answers — £340 a month, nothing at all, or “we paid £6,000 and I’m still not sure it was worth it.” All three can be true. The savings from a refinance depend on your old rate, your new rate, how long you stay in the house, and how much of your equity you hand back to the lender in fees.
So instead of a vague “it depends,” here’s the actual arithmetic, with realistic figures you can swap for your own.
The one number that decides everything: your break-even point
Refinancing costs money upfront — typically 2% to 5% of the loan amount once you add lender fees, appraisal, title work and recording charges. On a £250,000 mortgage, that’s roughly £5,000 to £12,500. You don’t “save” anything until those costs are paid off by the smaller monthly payment.
Here’s the sum:
Break-even months = total closing costs ÷ monthly payment reduction
Say you’re paying £1,480 a month at 6.4% on a £240,000 balance with 26 years left. You refinance to 5.5% over 25 years, the new payment drops to £1,290, and closing costs come to £6,200. That’s £190 a month saved, so you break even in 33 months — just under three years.
Stay in the house four years and you’re genuinely ahead by about £2,900. Sell or refinance again at month 20 and you’ve lost £2,400. That’s the whole game. Everything else — APR, points, term length — just moves those two numbers around.
Realistic savings by scenario
Dropping a full percentage point on a large balance
A 1% rate cut on a £300,000 balance saves roughly £180–£200 a month on a like-for-like term. Over five years that’s around £11,000 in payments, minus £7,000 of costs — net roughly £4,000. Modest, but real.
Getting out of an adjustable-rate mortgage before it resets
This is where the numbers get big. If your ARM is due to jump from 4.25% to a cap of 7.25% on a £280,000 balance, the payment climbs by about £520 a month — over £6,000 a year. Locking in before the reset can preserve most of that. Timing matters enormously here, which is why it’s worth reading about when refinancing an adjustable-rate mortgage actually pays off before your adjustment date creeps up.
Dropping mortgage insurance
If you bought with 10% down and the property has since risen in value, a refinance can get you under the 80% loan-to-value line and kill PMI. On a £260,000 loan, private mortgage insurance at 0.7% is about £150 a month — £1,800 a year, gone. Stack that with a rate cut and the break-even can fall under 18 months.
Shortening the term
Moving from a 30-year to a 20-year loan usually raises your payment, so there’s no monthly saving at all. The saving is in total interest — often £70,000 to £100,000 on a mid-size balance. A 20-year refinance sits between the two extremes, trimming years without the payment shock of a 15-year.
What refinancing actually costs, line by line
Lenders advertise rates, not bills. Here’s what shows up at closing on a typical £250,000 refinance:
- Origination fee: 0.5%–1% of the loan (£1,250–£2,500), sometimes waived in exchange for a higher rate
- Appraisal: £400–£700, occasionally waived on streamlined programmes
- Title search and insurance: £700–£1,500, and worth shopping around
- Recording and courier fees: £100–£250
- Prepaid interest and escrow funding: often £1,000+, though this isn’t a true cost — you’d have paid it anyway
That last point catches people out. Your closing disclosure will show a large “cash to close” figure that includes taxes and insurance you’d have paid regardless. Judge the refinance on the fees only, not the whole pile.
The trap: stretching the term to lower the payment
Resetting a 24-year remaining loan back to 30 years will always shrink the monthly payment — and it’s the most common way people convince themselves they saved money when they didn’t.
Drop from 6.5% to 5.25% but stretch from 24 years back to 30, and a £230,000 balance gives you a payment fall of about £215 a month. Feels great. Except you’ve added six years of payments, and total interest over the life of the loan can end up higher than if you’d never refinanced. You bought cash flow, not savings. That’s a legitimate choice — just don’t call it a saving.
If you want the lower payment without the extra years, ask the lender to match your remaining term. Many will. Or look at a short-term refinance, where the trade-off between cost and saving is clearer.
Where the rate comes from — and why shopping matters more than timing
The gap between the best and worst offer on the same day, for the same borrower, is routinely 0.6% to 0.9%. On a £250,000 loan that’s £90–£140 a month — more than most people gain by waiting six months for rates to dip. Getting three quotes and one broker comparison beats trying to call the bottom of the market, and it’s worth checking where refinance rates currently sit and what they’d actually save you before you commit to a lender.
Fixed versus variable is the other fork. A fixed-rate refinance buys certainty, not always the lowest number — you’ll often pay a small premium for it. On a £300,000 balance, 0.25% is about £45 a month, or £2,700 over five years. Whether that insurance is worth it depends entirely on how badly a payment increase would hurt.
Sometimes the answer is don’t refinance at all
If your existing rate is already at or below current market rates, refinancing is a straight loss. Same if you’re planning to move within two years, if your credit has slipped since you bought, or if the balance is small enough that fixed fees dominate.
There’s also a middle option plenty of people overlook: a mortgage recast lowers your payment without refinancing — no credit check, no appraisal, usually a few hundred pounds. It won’t cut your rate, but if cash flow is the actual problem, it can solve it for a fraction of the cost.
Running your own numbers in ten minutes
Pull three figures: your current balance, your current payment, and the closing costs on the offer in front of you. Divide costs by the monthly difference to get your break-even in months. Then ask yourself honestly how long you’ll keep this loan — not how long you’d like to.
If the break-even lands comfortably inside that window, refinancing is a straightforward win. If it’s close, or the saving only appears because you added five years to the term, walk away. The best refinance is the one where the maths still works if you sell early — because a surprising number of people do.