The Real Cost of Owning Your Home

Why doesn't my mortgage payment tell me the real monthly cost of owning a home?

A mortgage offer only ever quotes one number: the repayment on the loan itself. It says nothing about buildings and contents insurance, what a house realistically costs to maintain, or council tax. If you're buying leasehold, it says nothing about the service charge either. Lenders aren't hiding this deliberately; it simply isn't their job to budget your whole household outgoings, only to check you can service the debt.

Take the calculator's own default example: a £280,000 property with a £210,000 mortgage balance at 4.57% over 25 years. The repayment alone comes to roughly £1,176 a month. Add £220 a year of buildings and contents insurance, a £2,800 a year maintenance budget, £0 service charge (it's freehold) and £160 a month council tax, and the true monthly outgoing rises to around £1,587: over £400 a month on top of the figure the mortgage offer shows you.

If you're budgeting off the mortgage quote alone, you're underestimating what this house costs you every month by several hundred pounds, and that gap is exactly what catches people out in year one.

How much should I actually budget for maintenance and repairs?

Maintenance is the line first-time buyers underestimate hardest, because nothing obviously breaks in the first few months. A widely used rule of thumb, also used elsewhere on this site, is to budget around 1% of the property's value a year for repairs and upkeep. That's exactly where the calculator's £2,800 default comes from on a £280,000 home.

That figure isn't padding: a replacement boiler alone can run to £2,000–£4,000 depending on the type and property (Which?, 2026), and that's before guttering, a leaking roof valley, or a failed damp-proof course. Check likely figures for your own home with the boiler cost calculator before you finalise a maintenance budget. Budget nothing for maintenance and the first genuine repair bill wipes out months of "spare" income in one go.

If your own maintenance line is £0 or a token amount, the calculator's total monthly cost is understating your real exposure. Put a realistic figure in before you decide what you can afford, not after something breaks.

Freehold or leasehold: why does the service charge line change everything?

The calculator's default is freehold, with £0 in the service charge and ground rent field, which is why the maintenance budget carries so much weight in that example. Buy leasehold instead (most flats, and a growing number of new-build houses) and you're taking on a separate monthly service charge that a mortgage quote never shows you, on top of whatever ground rent survives on the lease.

Service charges vary hugely by building, from under £100 a month on a small, well-run block to £300-plus a month where there's a lift, communal heating or a managing agent adding margin. Two flats at the same purchase price can have genuinely different true monthly costs purely because of what's on the service charge demand.

If you're comparing a leasehold flat against a freehold house at a similar price, run both through this calculator with their real service charge figures: the freehold option is very often meaningfully cheaper to actually live in, not just to buy.

What this means for you

Once you've added insurance, a realistic maintenance budget, service charge (if applicable) and council tax to the mortgage payment, you have the number that should actually drive what you offer on a property, not the number a lender says you can borrow. Most people who run these numbers end up affording meaningfully less "house" than their mortgage in principle suggests, once the true monthly cost is on the table.

If you're stretching to the very top of your borrowing to hit a target price, the maths points toward buying a slightly cheaper property and keeping headroom for the maintenance and insurance lines this calculator surfaces, rather than finding out about that headroom the hard way in month four.

Run your actual numbers through the calculator before you make an offer, not after you've exchanged. It's the only point in the process where the figure can still change your decision.

Should I use this before I offer on a house, or after I've completed?

Before, ideally, and then again every year you own the property, because insurance premiums, maintenance needs and council tax bands all drift over time. Run it before you offer and the total monthly figure becomes part of your affordability decision, alongside what a lender will actually let you borrow. Run it only after completion and you've already committed to a monthly outgoing you hadn't properly sized up.

It's also worth revisiting once you're settled in: pair it with a home maintenance calendar so the annual budget you enter here isn't a guess but reflects what's actually due (a boiler service, gutter clearing, a roof check) in the year ahead. New buyers should also work through the new homeowner checklist alongside this tool, since several of the costs on that list feed directly into the fields here.

Treat this as a pre-offer affordability check first and an annual budgeting habit second. Used only once, after the fact, it can tell you what went wrong but not help you avoid it.