Bluetooth, Wi-Fi or a hub: which smart lock connection you need

A smart lock is two products sharing one shell. There is the mechanical half, which throws a bolt into a jamb, and there is a radio, which decides who is allowed to talk to the lock and from how far away. Most buyers give their attention to the first half, pick the model that looks right on the door, and find out a month later that the lock has nothing to say to them while they are at work.

The radio is the part worth slowing down for. It sets whether you need a second box plugged in somewhere down the hall, whether the app does anything useful once you are more than a room from the door, and how often you are back in the drawer looking for fresh AAs. Nearly everything else printed on the box is downstream of that one choice.

What the radio decides, and what it doesn’t

A radio does not make a lock harder to break. The same deadbolt with a Bluetooth chip inside and with a Wi-Fi chip inside resists a shoulder identically, because that resistance lives in the bolt, the strike plate and the length of the screws holding the strike into the framing. What the radio changes is reach and appetite.

Four practical things follow from it:

• Whether the lock can reach the internet by itself, or needs a hub, bridge or border router sitting somewhere else in the house.
• Whether you can see and change the state of the door while you are not standing at it.
• Whether a voice assistant or a home automation can be told what the lock is doing.
• How much of every set of batteries goes on listening rather than on driving the bolt.

If you have not settled on a category yet, the earlier question is which of the five distinct things sold as keyless entry suits your door, and it narrows this one considerably. A mechanical pushbutton lock has no radio to argue about at all.

Bluetooth: short range, long life

Bluetooth Low Energy is the default radio in the cheapest connected locks and in most retrofit units, the kind from makers like August and SwitchBot that clamp over the interior thumbturn and leave your existing cylinder and keys alone. The lock keeps its codes and its user list in its own memory. Your phone talks to it directly, over roughly fifteen to thirty feet in the open and rather less through a solid door with a metal skin, and the lock sleeps between conversations.

That sleeping is the entire advantage. A Bluetooth lock spends most of its life doing nothing, waking on a short interval to check whether a paired phone is nearby. Manufacturers commonly quote six to twelve months on a set of alkaline AAs for this arrangement, and owners tend to report figures in that neighborhood rather than dramatically under it.

Where Bluetooth stops being enough

Everything a Bluetooth lock does, it does within a few strides of the door. You cannot check from the office whether the door locked behind you. You cannot let a plumber in from a meeting. You can usually create a guest code in the app, but a phone has to carry that code to the lock over Bluetooth before it exists on the door, which defeats the purpose if the guest is arriving while you are two hours away.

Auto-unlock deserves a mention here because it is the feature people buy Bluetooth locks for and the one they complain about. It works as a geofence in the phone app, which notices you leaving the neighborhood and arriving back, plus a Bluetooth handshake at the door. The handshake is where the awkward pause on the step comes from, and it is also why the door sometimes unlocks itself when you walk past the inside of it with your coat on. That pattern of unwanted unlocks has its own troubleshooting checklist, from a geofence set too wide to an automation nobody remembers writing.

Wi-Fi: reaches everywhere, drinks accordingly

A Wi-Fi lock joins your home network the way a laptop does and talks to the manufacturer’s servers from there. After that the app works from anywhere with a signal: current lock state, a log of which code opened the door and when, codes created and killed from two states away, and assistant platforms that can see the lock without extra hardware. For most people that list is the reason to spend the extra money. A security system is usually not one of those platforms by default, as the SimpliSafe compatibility guide explains.

Two things about Wi-Fi locks are worth knowing before the box is open.

The 2.4 GHz rule that stops half of these setups

Nearly every Wi-Fi lock is 2.4 GHz only. Routers now ship with the 2.4 and 5 GHz bands sharing a single network name and quietly steering devices between them, and a lock that cannot see 5 GHz will often refuse to finish setup, or finish it and then fall off. The usual answers are to split the bands into two names for the duration of pairing, turn off band steering, or give the lock a dedicated 2.4 GHz network name and leave it there permanently. Mesh systems add a wrinkle of their own, since the lock pairs against whichever node it can hear and may be handed to another later. If you are already past setup and the lock drops every night, that pattern has its own list of things to check in order.

What always-on listening costs

Holding an association to an access point is not free. Wi-Fi locks are commonly quoted at two to six months where a comparable Bluetooth model is quoted at a year, and the real number depends on how often the lock checks in, how far it sits from the router, and how hard the motor is working against a bolt that binds. Cold weather shortens all of these figures. Which cell chemistry behaves how, and what actually drains a lock fastest, is covered in the battery guide.

The bridge, sold as an accessory, is really a third option

Several makers sell a plug-in bridge: a small mains-powered box that sits in an outlet within Bluetooth range of the door and relays between the lock and your Wi-Fi. The lock stays a Bluetooth lock and keeps most of its battery life, while the bridge, which has an outlet behind it and no battery to worry about, does the tiring part.

For a lot of houses this is the sensible middle, with two caveats. A bridge is typically another thirty to eighty dollars on top of the lock, though prices move around by market and by month, so treat that as a rough band rather than a quote. And bridges are brand-specific: one maker’s bridge will not adopt another maker’s lock, so buying the bridge later means you are locked into the same brand you started with.

Z-Wave, Zigbee, Thread and Matter, in brief

Three more radios turn up on spec sheets, and each one assumes a piece of infrastructure you may or may not already own.

Z-Wave is the old guard of hub-based home automation. It uses a sub-gigahertz band that gets through interior walls better than 2.4 GHz does, and it will never talk to a phone unaided. A controller is not optional. Which hubs still pair locks, and what the Plus and Long Range labels on the packaging mean, is set out in the Z-Wave hub guide.

Zigbee is the other mesh radio, on 2.4 GHz, equally hub-dependent, and these days more often found inside hubs and bridges than named on the front of a lock box.

Thread is the newer low-power mesh. It needs a border router on the network before it can reach anything beyond itself, and plenty of households already have one hiding inside a speaker, a streaming box or a mesh node without ever having been told.

Matter is not a radio. It is a shared language spoken over Wi-Fi or over Thread, so it says nothing about range or battery life on its own. A Matter over Thread lock still needs the border router. A Matter over Wi-Fi lock still needs the 2.4 GHz network to behave.

What still works when the internet is down

This is where the marketing copy goes vague, and the honest answer is more reassuring than people expect. Keypad codes live on the lock itself on essentially every model worth buying, so a code punched into the door works with the router unplugged, the line cut and the manufacturer having a bad afternoon. The physical key works, if the lock kept a cylinder. The interior thumbturn works.

What stops is anything that had to travel. On a Wi-Fi lock the app cannot reach the door from outside the house, so remote unlocking, code changes made from elsewhere, arrival notifications and voice commands all fail together. A Bluetooth lock is unaffected as long as you are standing at the door, because none of that was going through the internet in the first place. A power cut produces the same result by taking out the router while the lock, running on its own batteries, carries on locally.

The lock with no radio at all

Worth saying plainly, because the category is usually skipped: an electronic keypad deadbolt with no connectivity is a legitimate answer and not a downgrade. It holds a set of codes, runs a year or more on alkalines, costs less, and cannot be reached over any network because there is no network interface to reach. If the thing you actually wanted was to stop hiding a key under the pot by the step, that is the job finished.

The reasons to add a radio are remote access, an activity log and automation. If none of those are things you will genuinely use in the second month, the radio is a battery cost and a setup evening you are paying for twice.

Matching the radio to the household

A rough sorting, in the order the decision usually falls out:

• Nobody needing to be let in while you are out, no interest in logs, a door you always walk up to yourself: keypad-only, or Bluetooth if you want the app for code management.
• Cleaners, dog walkers, deliveries taken into a porch, or a code you may need to revoke from a hotel room: Wi-Fi, or Bluetooth plus a bridge.
• A hub already running blinds, sensors and lights: Z-Wave or Zigbee, so the lock joins the system you have rather than starting a second one.
• An Apple, Google or Amazon household with a recent speaker or streaming box: Matter over Thread usually means the least new hardware, provided you confirm the border router before buying.
• A door far from the router, thick masonry walls, or a detached garage: a sub-gigahertz Z-Wave mesh, or a bridge sited closer to the door, beats fighting Wi-Fi coverage at the doorstep.

Common questions

Do smart locks need Wi-Fi?

No. Bluetooth locks, Z-Wave locks and plain keypad locks all work without the lock itself ever joining a Wi-Fi network. What needs Wi-Fi, or a hub with an internet connection behind it, is anything you want to do to the door from somewhere other than the doorstep.

Will a Bluetooth lock open if my phone battery is dead?

Yes, by any other method the lock has. That is the practical reason to avoid app-only models with no keypad and no cylinder: the phone becomes a single point of failure for a door you have to get through. Almost every lock ships with at least two ways in for exactly this reason.

Can I add Wi-Fi to a Bluetooth lock later?

Sometimes, and only within the same brand. If the manufacturer sells a bridge that lists your model as supported, adding it later works fine. If they do not, there is no universal adapter that will do the job, so check the bridge compatibility list before buying the lock rather than after.

Which is safer, Bluetooth or Wi-Fi?

They fail differently rather than one being clearly safer. A Bluetooth lock has no route in from outside your street, but an attack on it only requires proximity. A Wi-Fi lock is reachable in principle from anywhere, which puts the weight on your account security: a unique password and two-factor authentication on the lock app matter more than the radio choice does.

Does a Wi-Fi lock keep working in a power cut?

The lock does, since it runs on its own batteries. The router does not, so the lock effectively becomes a keypad lock until power returns. Codes, key and thumbturn all keep working throughout.

The short version

Bluetooth is cheap and frugal and stops at the door. Wi-Fi reaches everywhere, costs you battery life, and will have an argument with your router about 2.4 GHz on the first evening. A bridge buys most of the Wi-Fi benefit while leaving the lock on Bluetooth power draw, at the price of another box in an outlet and a permanent commitment to one brand. Z-Wave, Zigbee and Thread are all infrastructure propositions, sensible if you already own the hub or the border router and a nuisance if you do not. Decide by whether you truly need to do something to that door while you are not standing at it, because if the answer is no, the simplest radio is the one that lasts longest.