Portsmouth is unusual among English cities: most of it sits on Portsea Island, one of the most densely built-up places in Europe. That geography shows up directly in the sale figures. Across 2,445 completed home sales in 2025 (HM Land Registry Price Paid, standard "category A" transactions of houses and flats), the median Portsmouth property changed hands for £259,000 — but what you pay depends heavily on which of the city's six postcode districts you buy in.
The dearest is the one that isn't on the island at all.
The outcode ladder
| Postcode | Area | 2025 median | Sales |
|---|---|---|---|
| PO5 | Southsea, Somerstown | £222,000 | 327 |
| PO1 | City centre, Landport | £223,000 | 225 |
| PO2 | North End, Hilsea | £240,000 | 501 |
| PO4 | Eastney, Southsea East | £267,075 | 616 |
| PO3 | Copnor, Baffins | £280,000 | 301 |
| PO6 | Cosham, Drayton, Farlington, Paulsgrove | £310,000 | 470 |
Five of those six districts — PO1 to PO5 — cover Portsea Island itself. PO6, the priciest at a £310,000 median, is the mainland strip to the north: Cosham, Drayton, Farlington, Paulsgrove and the Port Solent marina. The gap between the cheapest island district (PO5) and the mainland (PO6) is £88,000, or 1.40 times. That still leaves Portsmouth one of the most geographically even-priced cities in England — it topped our ranking of the UK cities with the flattest price geography.
Why the mainland costs more — it's the houses, not the prices
Here is the part that matters if you're weighing up the two sides. A mainland postcode is not simply a more expensive place to buy the same thing. Break each district down by property type and the picture changes.
| Postcode | Detached | Semi | Terraced | Flat |
|---|---|---|---|---|
| PO1 (island) | 0.4% | 2.2% | 62.7% | 34.7% |
| PO4 (island) | 1.0% | 6.8% | 71.1% | 21.1% |
| PO5 (island) | 2.8% | 7.6% | 33.3% | 56.3% |
| PO6 (mainland) | 12.1% | 38.9% | 32.3% | 16.6% |
The island is a terrace-and-flat city. In PO1, terraced houses and flats made up 97% of 2025 sales, and just one of its 225 sales was a detached house. The mainland is different: in PO6, more than half of sales (51%) were semi-detached or detached houses — the kind of stock Portsea Island is simply too dense to hold much of.
Now compare like with like. Take PO4, the island's busiest district by volume, against mainland PO6:
| Type | PO4 (island) | PO6 (mainland) |
|---|---|---|
| Flat | £175,000 (130 sales) | £178,250 (78 sales) |
| Terraced | £274,000 (438 sales) | £298,500 (152 sales) |
A flat costs roughly £175,000 whether you buy it on the island or the mainland — the difference is about £3,000. Across the whole city, flat medians run from £166,750 (PO5) to £183,750 (PO1), a narrow band on either side of the harbour. Terraced houses are closer than the headline £88,000 gap suggests, too.
What lifts PO6's median is the house types the island barely offers. Its semi-detached homes sold at a £338,000 median (183 sales) and its detached houses at £585,000 (57 sales) in 2025. And the single clearest number is this: of the 93 detached houses sold across the whole of Portsmouth in 2025, 57 — almost two-thirds — were in PO6 alone. The other 36 were scattered thinly across the five island districts. Portsmouth's detached-house market is, in effect, a mainland market.
The mainland isn't greener
A reasonable guess would be that the newer mainland estates are also more energy-efficient, adding to their appeal. The Energy Performance Certificate data doesn't bear that out. The share of homes rated C or above — the EPC band most buyers look for — is remarkably even across the city, based on the latest certificate held for each address:
| Postcode | Homes rated C or above |
|---|---|
| PO3 (island) | 38.2% |
| PO1 (island) | 36.2% |
| PO6 (mainland) | 34.8% |
| PO5 (island) | 32.2% |
| PO4 (island) | 30.6% |
| PO2 (island) | 28.8% |
Mainland PO6, at 34.8%, sits in the middle of the pack — below two island districts. Portsmouth is a largely pre-war city on both sides of the harbour, and older solid-wall stock tends to rate lower wherever it stands. (EPC running-cost estimates are modelled figures and don't map directly onto a household's actual energy bill; treat them as a guide to the building fabric, not a quote.)
Council tax is the same wherever you buy
One cost does not vary between the island and the mainland at all: council tax. Portsmouth is a single unitary authority, so every one of its postcodes carries the same Band D charge of £2,291.71 for 2026-27 (Portsmouth City Council) — below the £2,410.97 average across England's 296 billing authorities.
That has a neat consequence. Because council tax is identical citywide, the difference in monthly running cost between areas is almost entirely the mortgage. Using the Bank of England's most recent quoted rate for a five-year fix at 75% loan-to-value (4.32%, April 2026), a 25-year term and a 25% deposit:
| Location | 2025 median | Est. mortgage/mo | Council tax/mo | All-in/mo |
|---|---|---|---|---|
| Island median (PO2) | £240,000 | £982 | £191 | £1,173 |
| Citywide median | £259,000 | £1,060 | £191 | £1,251 |
| Mainland median (PO6) | £310,000 | £1,269 | £191 | £1,460 |
Figures exclude energy, insurance, maintenance and any leasehold service charge, which vary property to property; your own rate will depend on your lender, deposit and circumstances. The mainland median runs about £287 a month more than the island median — and every penny of that gap is mortgage, not council tax.
The stamp duty line
The island/mainland divide is quietly a stamp duty line, too. At the island's £240,000 median a home mover pays £2,300 in Stamp Duty Land Tax and a first-time buyer pays nothing, because the price sits under the £300,000 first-time-buyer nil-rate band (HMRC, 2026). Cross to PO6's £310,000 median and a first-time buyer is nudged just over that threshold — £500 due. A mainland detached house at £585,000 takes even a first-time buyer to £19,250, because first-time buyer relief is withdrawn entirely above £500,000.
| Price | Home mover | First-time buyer | Additional property |
|---|---|---|---|
| £175,000 (island flat) | £1,000 | £0 | £9,750 |
| £240,000 (island median) | £2,300 | £0 | £14,300 |
| £310,000 (PO6 median) | £5,500 | £500 | £21,000 |
| £585,000 (PO6 detached) | £19,250 | £19,250 | £48,500 |
The "additional property" column is the 5% surcharge that second-home and buy-to-let buyers pay on top of the standard rate.
What this means for a Portsmouth search
If you're comparing neighbourhoods, the shorthand that "the mainland is dearer" can mislead. A one- or two-bed flat costs much the same in Cosham as it does in Southsea, and a Victorian terrace not hugely more. What the mainland offers is the semi-detached and detached houses the island is too built-up to provide — and it's those, not a location premium on identical homes, that pull PO6's average up.
You can see the all-in cost for any specific street on the Homecost tool. Compare a mainland address like Cosham, PO6 1AA with an island one like Southsea, PO5 3AT to see how mortgage, council tax, energy and stamp duty stack up side by side. To model the monthly payment on the £310,000 mainland median, open the mortgage calculator.
For the wider picture, see our Portsmouth house price guide, the Solent-coast comparison with Southampton and Bournemouth, or how the gap between a city's average and typical home plays out nationally. More area guides sit under Regional Prices.
These figures come from 2,445 HM Land Registry Price Paid transactions for Portsmouth in 2025 and the 2026-27 council tax set by Portsmouth City Council, retrieved on 15 August 2026. You can browse all our property cost guides.
This is general information, not financial, tax or property advice. House prices reported here are what buyers paid, not valuations of any individual property. Speak to a qualified adviser before acting.