What a house actually costs per month
IMI, condomínio, two insurances, and the repairs that arrive on their own schedule — the costs beyond the prestação, and how to stop them surprising you.
By António Avelar Updated 19 August 2026 3 min read
Ask someone what their house costs and they quote the prestação. It is the number they see monthly, so it feels like the answer — and it is usually short by two or three hundred euros.
The rest hides in plain sight: some of it annual, some quarterly, some arriving only when something breaks. None of it is optional. A budget that only knows the prestação is a budget that gets surprised on schedule.
The recurring cast
IMI. The municipal property tax, calculated on the taxable value of the house at a rate the municipality sets each year. It arrives in one, two or three instalments — typically May, August and November — depending on the amount. It is the classic ambush cost: absent for months, then a few hundred euros with a deadline.
Condomínio. For apartments, the monthly quota — and, less famously, the occasional quota extraordinária when the building needs a roof, a lift, a paint job. The monthly number is easy to track; the extraordinary one is why buildings with healthy reserve funds are worth paying slightly more into.
The two insurances. Multi-risk home insurance is legally required for apartments and required by the bank if there’s a mortgage; life insurance rides along with the loan. Both drift upward at renewal and both reward an annual re-quote.
Utilities and their standing charges. Water, electricity, gas each carry a fixed component you pay before consuming anything. Worth knowing, if only so a low-usage month no longer looks like a billing error.
The irregular cast
Things break on their own schedule: the water heater, a window seal, the fridge. Owners also pay for what a landlord would have absorbed — there is no one to call.
The useful convention is a maintenance reserve of roughly 1% of the property’s value per year, set aside whether or not anything broke. On a €200,000 home that is around €160 a month. Some years you spend none of it; the year the roof leaks, you spend three of them at once. The reserve converts a crisis into a withdrawal.
The trick is annualising
The reason these costs surprise people is not their size but their rhythm. IMI is invisible in March and unmissable in May. A quota extraordinária lands once and wrecks a month that was otherwise fine.
The fix is to treat every one of them as a fixed cost, because that is what they are — fixed in obligation, merely irregular in timing. Add up the year — IMI, insurances, condomínio including a guess at the extraordinary, the maintenance reserve — and divide by twelve. That monthly figure, alongside the prestação, is what the house costs.
Two practical notes. The subsidy months exist for exactly this shape of expense — IMI in May and insurance at renewal are natural claims on them. And the annualised number is worth knowing before buying, too: it is the difference between a prestação you can afford and a house you can afford.
Run the total once
Most owners have never added it up — the costs leave from different accounts, under names the statement does not explain, on schedules that never line up. Gathering a year of them takes one evening.
The result is a single honest number. It is always higher than the prestação, and knowing it is the difference between a house that fits the budget and a budget that keeps being ambushed by the house.