The short answer for a flat

Buy WiFi for the jobs where a hub would be the only reason you own a hub: a couple of lamps, a smart plug or two, a bulb in the hall. Those run today on the router you already have.

Where that stops scaling is more concrete in a flat than most guides admit. Hyperoptic, the ISP that wires up a lot of UK blocks, is one of the few to publish a figure. Its FAQ says its Hyperhub routers "can support four wired devices and 32 wireless devices on a 2.4Ghz frequency, as well as 32 wireless devices on a 5Ghz frequency". Every WiFi bulb, plug and sensor is a 2.4GHz client, and phones, laptops and the TV are already in that pool.

Zigbee devices are not. They talk to a coordinator, and the coordinator is the single client your router sees. Two other things tilt it once you go past lamps: Zigbee generally lasts longer on the same batteries, because it avoids IPv6 overhead and can sleep for longer, and one 2026 comparison on identical sensor hardware put it at roughly three years against two. A Zigbee network also keeps working when your broadband drops, which a cloud-dependent WiFi plug does not.

So this is not a per-device choice. It is one hub decision, made once.

Both radios sit on 2.4GHz, and UK channel 13 changes the advice

Most pages frame congestion as a WiFi problem that Zigbee escapes. It is not. Zigbee has 16 channels numbered 11 to 26, each about 2MHz wide and spaced 5MHz apart, sitting inside the same 2400 to 2483.5MHz band your router uses. In a block of flats that band is the scarce resource and both options are queueing for it. Ofcom's Interface Requirement 2030 lists wideband 2.4GHz data systems at 100mW EIRP under EN 300 328, a standard whose scope covers the 802.15.4 radio Zigbee uses as well as WiFi, so articles describing WiFi as vastly more powerful are describing American limits.

Here is where nearly every guide gets the UK wrong. The standard advice is to put Zigbee on channel 25 or 26, and Digi's own channel reference marks both as having no WiFi conflict. That column assumes the American plan, where WiFi stops at channel 11. IR 2030 defines the UK band with no channel restriction, so WiFi channel 13 is in normal use here, spanning 2462 to 2482MHz. That covers Zigbee 24, 25 and 26. WiFi channel 12 covers Zigbee 23, 24 and 25.

So the only two Zigbee channels that clear WiFi 1, 6, 11, 12 and 13 in a UK block are 15 (2425MHz) and 20 (2450MHz). Be honest about the margin: against the older 22MHz WiFi mask they sit 1 to 3MHz clear of the nearest edge, a gap rather than a wall. Still worth taking: Silicon Labs measured its parts tolerating "up to 20dB stronger Wi-Fi signal in 'far-away' channel case than in adjacent channel case". Twenty dB is a factor of a hundred in power.

Three things follow that no ranking page tells you:

• It will not fix itself. The Zigbee network manager function that could shift your mesh to a quieter channel is, in Silicon Labs' words, "not a mandatory feature", and is often absent. Pick the channel when you first set the coordinator up, because changing it later usually means re-pairing everything.
• Keep the coordinator off the router shelf. Control4's own installer guidance is blunt: "Always move the WiFi router or access point at least 5 meters (15 feet) away from the mesh controller." A co-located router can drown it even on a non-overlapping channel, and in a one-bedroom flat that is a real constraint.
• Use a shielded USB extension lead. USB 3 ports are a recurring suspect in Zigbee instability on the Home Assistant forums, and moving the dongle clear of the machine is the standard fix.

Zigbee needs a hub, and Thread does not remove it

This is the real cost difference, and listings bury it. A Zigbee device needs a coordinator. In the last hundred reviews for the SONOFF ZBMINIL2 no-neutral switch, seventeen are one star, and a large share are people who never got it to pair, several of them hunting for it on their WiFi network. One bought a standalone hub after hours of failing and edited a one star up to four. Nothing about the product changed.

Two hub traps our own review turned up, both worth settling before you order:

• A Zigbee 3.0 badge does not mean any Zigbee hub will take it. Five reviewers in the last hundred mention Philips Hue, and all five report that the ZBMINIL2 will not pair with the Hue Bridge.
• Not every mains device extends the mesh. The ZBMINIL2 is a Zigbee end device rather than a router, and seven reviewers in the last hundred say so explicitly. Eleven report it dropping off the network. Budget for a mains-powered Zigbee repeater within range.

Now the myth that most needs killing: Thread does not get you out of buying a box. A Thread device needs a Thread border router. tado say it about their own Matter-over-Thread valve, "Your tado° X setup requires a Bridge X", and a third-party border router has to support NAT64, a requirement that appears on nobody's packaging. Nuki state the same for their locks. You are choosing which box to buy, not whether. Only WiFi devices genuinely need nothing extra.

With one caveat that catches people out. Every WiFi smart home device here is 2.4GHz only, and most current UK ISP routers broadcast a single merged name across 2.4 and 5GHz. Whether you can separate them to get a stubborn device on depends entirely on whose router you were sent. BT is explicit that you cannot: its own guide says "the Smart Hub 2 doesn't have this capability as it's designed for use with Complete Wi-Fi", and BT's split instructions cover only older hubs. Hyperoptic publishes a split guide for its Nokia and ZTE hubs but says it is "not recommended" on the current Zyxel Hyperhub. Community Fibre documents the split for both its routers and suggests putting smart home devices on 2.4GHz. Zigbee never touches your WiFi network name at all, so the question simply does not arise.

Ignore the capacity numbers too. The claim doing the rounds is that Zigbee supports up to 65,000 devices, so you will never need a second network. That is a 16-bit address space, not a device count. The Connectivity Standards Alliance's own Zigbee FAQ, answering exactly that question, says "hundreds of nodes per network". Control4's installer guide carries the heading "Limit a mesh to 70 nodes". A SONOFF ZB Bridge-P is documented at 128 devices in total and 10 connected directly. None of that constrains a flat, but your hub sets the real ceiling, not the standard.

Check you have a radiator before you buy a smart valve

Smart radiator valves are the highest-value upgrade in a lot of UK homes, and in many UK flats not an option at all. Nesta's analysis of 5.6 million EPC records for flats in England and Wales found 45% of high-rise flats, meaning 11 storeys or more, on communal heating, and around 60% of flats in high-rise buildings using electricity for heating. Panel and storage heaters do not take a valve head.

The regulations moved recently, too. Regulation 6 of the Heat Network (Metering and Billing) Regulations 2014, the duty to install heat cost allocators, hot water meters and thermostatic radiator valves, was revoked in England, Scotland and Wales on 27 January 2026, and remains in place in Northern Ireland. So the regulations no longer promise that a communal-heated flat has thermostatic valves on its radiators at all.

Where there is a wet radiator, check the valve body rather than the radiator. A smart TRV is only the head: it screws onto an existing thermostatic body and pushes the pin, so it will not work on a plain manual wheelhead or on the lockshield at the far end. Our SONOFF TRVZB review found the compatibility promise resting on one word. The listing says it fits existing "M30 x 1.5mm" radiator valves and that the adapters are compatible with "most heating systems and manufacturers", and names not one valve brand. Danfoss RA, RAV and RAVL bodies, common in older British stock, use a proprietary fitting rather than M30. One buyer in that review found the valve cleared his wall by about 1mm, so measure the gap first.

Two more flat realities. tado describe the communal case bluntly, noting that the resident "has no access to the boiler", so a valve can restrict heat the building already circulates but cannot call for heat that is not being sent. And if your block runs a fixed heating season, the valve does nothing outside it.

What a rented or leasehold flat lets you fit, and what comes back off

Reversibility decides more of this than protocol. Ranked from safest to trickiest:

• Smart plugs. An appliance in an existing socket: nothing to notify, nothing to ask, nothing to restore. Our Eightree Mini Smart Plug review shows the limit. Neither the listing text nor any of its nine images states a maximum wattage or amperage, and our own steer is to skip it if you need a plug for a high-draw appliance and want a printed load rating before you commit. Lamps and small loads.
• Smart bulbs. A consumable rather than an alteration. The UK trap is the cap: much smart lighting is E27 screw, while British ceiling roses and lamps are frequently B22 bayonet. Our bayonet round-up found that filtering to B22 colour bulbs collapses the field to one serious option, the Tapo L530B, which is 2.4GHz WiFi only and does not support Matter.
• A screw-on smart valve head. Reversible only if the body underneath is already thermostatic. Keep the original head.
• An in-wall switch module. Physically reversible, contractually not. It alters the landlord's fixed electrical installation, so treat it as consent-required and bag the original faceplate.
• A video doorbell. Sold as the renter-friendly option because it is battery powered, and in a flat it is the least reversible thing here. The question is not the wiring, it is what you screw it to: a flat entrance door is usually a certificated fire door and the wall beside it is communal fabric.

On the paperwork, and none of this is legal advice. England's Approved Document lists three notifiable jobs: a new circuit, a consumer unit replacement, and an addition or alteration in a special location. A kitchen is not a special location in England, though non-notifiable is not unregulated and the work still has to comply. Wales runs its own older document, in which extensions to circuits in kitchens are notifiable and "New central heating control wiring installations are notifiable even where work in kitchens and bathrooms is avoided". Scotland uses building warrants instead, and the Scottish Government's own research report describes warrant requirements applying to flats that houses of up to two storeys are exempt from. Electrical Safety First states there are currently no statutory requirements for domestic electrical installation work in Northern Ireland.

On consent, the Landlord and Tenant Act 1927 says a lease clause forbidding improvements without consent is read as consent not to be unreasonably withheld, and preserves the landlord's right to require an undertaking to put the place back as it was. Photograph the switch plate, the valve and the door first.

If a doorbell camera covers the shared landing, the ICO's guidance is that data protection law applies. Its own worked example is a neighbour's door camera covering a communal hallway, and the answer is not a ban but a set of duties: signage, capturing no more than needed, deleting footage, answering requests. Households are exempt from the data protection fee. Turning audio off is the highest-value setting in a block.

Where Matter fits, and what we would actually put in a flat

Matter is not a radio and it is not Zigbee's rival. It is an application layer running over WiFi, Thread, Ethernet and Bluetooth, and the Connectivity Standards Alliance describes Matter and Zigbee as "different protocols, giving product makers different options". Bridging is built in by design, so a hub can carry Zigbee devices into a Matter ecosystem. The real comparison is Thread against Zigbee against WiFi, with Matter sitting on top of two of them.

Is buying Zigbee now a dead end? No, and there is a dated answer rather than an opinion. The CSA released Zigbee 4.0 on 18 November 2025, backward compatible with Zigbee 3.0 and extending the standard beyond 2.4GHz to 800MHz in Europe, alongside a new sub-GHz brand called Suzi whose certification programme was planned to open in the first half of 2026. No page ranking for this search mentions any of it; one still calls the organisation the Zigbee Alliance, a name dropped in May 2021, and calls Zigbee 3.0 an emerging standard.

The honest case on the other side: IKEA announced 21 Matter-over-Thread devices in November 2025 and stopped launching new Zigbee products, so the direction of travel is real, and Matter support is still uneven across Apple, Google, Amazon and SmartThings. The Zigbee kit you buy today will not turn into Thread kit later. Your hub bridges it into Matter instead, which is a supported path rather than a workaround.

What we would put in a flat, then:

• Buy the hub, not the protocol. One box that is both a Zigbee coordinator and a Matter controller lets you buy whichever device is best per job. One trap: a single-radio dongle such as the Home Assistant Connect ZBT-2 "can only use one protocol at a time", so Zigbee and Thread together means two dongles or a hub with two radios.
• WiFi for lamps and plugs, on the 2.4GHz band, checking the bulb cap first.
• Zigbee for heating, sensors and anything at the wall. The Zigbee valve and switch market is deep and cheap. Matter-over-Thread valves exist, the tado Smart Radiator Thermostat X being the best-known in the UK, but the category is far thinner and pricier.
• Let reversibility win ties. In a rented flat, a module you can undo in ten minutes beats the radio inside it.