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Most smart locks replace all or part of the lock mechanism, which is usually an easy DIY job. For homes like mine that have a combination latch and bolt system, that’s not practical. The Nuki Smart Lock fits in that niche and allows it to be used with combination door hardware common in Europe and some other countries.

By fitting over the existing key hole and using the key itself to work the lock, the Nuki system offers a flexible and easy to install option. In cases like mine it avoids the need to completely replace the whole lock system and drill more holes in the door, but it does come with some downsides in terms of it’s operation and bulk when compared to more conventional smart locks.

Nuki Smart Lock

✔ Extensive smart home integrations
✔ Compatible with Euro/UK/Swiss profile locks
✔ Easy installation
✔ Manual Override
✔ Multi-user support
✘ Bulky, check door handle clearance
✘ A little noisy

Up Front Considerations

What Lock Type do you have?

The biggest consideration when looking at the Nuki is what kind of lock you have. The Nuki is designed to fit over the existing lock without removing anything. This means it supports a bunch of locks that otherwise couldn’t be converted easily to smart locks, but it also means it’s not compatible with other types.

It comes down to whether the attachment method will work. Nuki provides a pretty comprehensive compatibility tool so you can be sure before purchasing. Basically you need enough clearance, and a lock profile that fits in the back plate that holds the lock onto the door. The plate comes in two types, either a one that grips the lock barrel itself, or simply uses an adhesive pad depending on the design of your lock.

Do you need a hub?

The Nuki uses Bluetooth natively, and that’s used to connect to the app, it’s various accessories, and provides native Apple HomeKit support. But for any other smart home integrations you’ll need the Nuki Bridge which connects it to WiFi as well. The bridge opens up a pretty impressive array of integration options, far more than any other smart lock I’ve seen.

What’s in the Box?

There’s no major surprises when opening the Nuki box. You’ll get the lock, a quick start guide and HomeKit code, and the two mounting plates (labelled A and B). The lock is powered by four AA batteries, which are included. There is a plastic tab you need to pull to activate the lock which protrudes from the battery tray cover on the underside of the lock, where it’s easily accessible once installed.

Along with the batteries, the actuator motor is inside the black portion, which is quite bulky. The top round portion contains a rotating slot to hold the key and a large knob around the status indicator LED circle, and the central button that toggles the lock.

The knob and key mechanism is cleverly designed so that you can manually rotate the key with the knob without affecting the motor, so you can freely use that manual method to lock and unlock the door interchangeably with the smart function, which can also be triggered manually by pressing the central button. The LED circle provides a simple indication of the lock status, a complete circle being locked, and missing the upper quarter when it’s unlocked.

Installation and Setup

While the installation is trivial, there is a bit to do with the setup. Thankfully it’s supported by an excellent set up process in the Nuki app that makes it all very clear and largely takes care of it for you.

The first thing to do select the correct mounting plate. My lock was actually recessed slightly into the door furniture, so I went with the adhesive one. I had some concerns it wouldn’t hold since the smooth surface I had available around the lock was smaller than the mounting plate, but that turned out to be a non-issue. It holds strongly and so far has not cause an issue.

The tricky part with the adhesive ‘B’ plate is getting it straight. You don’t the fitted lock looking crooked on the door (Well, I certainly didn’t). The clamping ‘A’ plate is easier since you hold onto the lock with three small screws tightened with the provided allen key. If you get it wrong, just loosen and adjust. With the adhesive, you get one shot.

It would be nice to have a small level included on the backing plate, similar to how Ring does with their doorbell mounting brackets, but as it is I had to get my own. Holding that against the plate while trying to position it was a bit awkward, but we got there.

That’s the hard bit. Once the plate is attached you insert the key into the lock, pull the battery tab on the lock and snap it onto the plate with a firm press. Now you’re ready to pair it with the app by holding the button on the front until the LED ring stays lit. This can take a little bit, and I ran into trouble here when the app crashed. My first thought was that I’d have to figure out how to factory reset and try again, but the app picked up that setup was incomplete and allowed me to resume, so that’s a nice feature.

The Nuki app steps you through setup well

Once paired, the app will step you through some options such as the name of the lock, the type of door hardware you have, a security PIN (for changing settings), and then it will conduct a calibration process so it knows how many rotations are needed to lock and unlock the door. That’s completely automatic, and you can adjust it later.

That’s the basic setup done, and you’re good to go. You’ll be given a checklist of other things you can optionally do, such as adding additional users, installing accessories like the included door sensor or adding a bridge, and setting up HomeKit. You can always come back to this later if you wish.

If you’re adding the bridge setup is equally simple. Plug it in, start the bridge setup in the app, press the button to allow it to connect and it takes care of the rest, including adding the existing lock to the bridge.

Nuki Smart Lock Features

Smart Integration Support

I specifically wanted a smart lock with HomeKit support, and Nuki offers this natively, but a bigger issue is that if you have the kind of door lock that needs the Nuki you’re going to be hard pressed for options. For this reason it’s good that Nuki has gone all out on smart integration support, so you’ll likely be covered whatever you are using.

This includes not only the big three, Apple HomeKit, Amazon Alexa, and Google Home, but a range of other significant platforms including Homey, Homee, IFTTT, Mediola, iHaus and more. They also offer direct integration with Ring and Doorbird doorbells so you can unlock the door right from those apps. Handy if there’s someone at your door you want to let in, but you’re not home.

As HomeKit support is via Bluetooth, you’re going to need a home hub close enough to get decent signal. Reliable and responsive Bluetooth connections in HomeKit really depend on a good implementation like Eve Systems has. In Nuki’s case it’s proven a bit slow, which means it can take a while to respond, and often Siri will say it didn’t respond only to have the lock activate a second later.

Using the Nuki’s keypad or fob accessories would mitigate this, but that’s a chunk of extra change. If you have an Apple watch you can acheive the same result with Nuki’s watch app. This provides a nice, simple interface with your available options (Like ‘Open Door’ and ‘Lock’) depending on the state of the lock, and it connects directly to the lock like the fob, which can be a bit quicker if you put it right on your watch face as a complication.

For the more hardcore you can use the bridge to connect via Wifi. It doesn’t support HomeKit natively, which is a shame, but you can use the third party Homebridge software to do it using the ‘homebridge-nb’ plugin. This adds some complexity, but if definitely responds faster and more consistently in my testing.

Uses your existing key

This is major selling point of the Nuki, as I’ve covered above. By using the key itself you don’t need to modify your existing lock at all, and it’s recommended to use it on a lock that allows a key to be inserted from both sides simultaneously. This ensures you can still use the key from the outside with Nuki installed.

This maximizes compatibility, but it also means it’s not as smooth an experience as a conventional smart lock that directly actuates the lock bolt. To be able to run turn the key and not flatten the batteries too quick, Nuki uses a highly geared motor. It allows the key to be turned through as many rotations as required, which varies by lock, and that’s good, but running the motor is also quite noisy, and it has to run for a few seconds, so it’s very noticeable as it whirrs along.

An issue I’ve encountered with this approach is that, because the Nuki is abstracted from the lock bolt (via the key), it doesn’t know the actual state of the lock, only what it thinks it is. So if you lock the door with the key from the outside, Nuki won’t know that if your inside and outside barrels are independent as mine are. If you can insert a key in both sides, and when you turn one the other doesn’t move, you’ll likely have the same issue.

An the other hand, because Nuki is using the actual key mechanism with these types of combo door locks you can actually open the door remotely as well. Depending on your calibration, the unlocking process can pull the bolt all the way back which unlatches the door as well.

Lots of Nuki app configuration options and logging

With my door hardware the latch and the lock bolt are one and the same. When unlocked, turning the handle pulls back the latch like a normal door. When locked it can’t, it’s blocked from turning. There’s also a push button lock that just blocks the handle from the outside, but allows it to turn and pop the button from the inside. We use the latter normally when we’re home for fire safety reasons.

The Nuki has been really handy with this arrangement (when it works) because I can tell my Apple Watch to ‘Open the door’ when my hands are full. The lock will pull the latch back, and I can just push it open. This only lasts a few seconds (configurable), and it will release the latch again, which is also cool as it ensures the door doesn’t blow open later. If the door was locked before, it will lock it again too. This is something you can’t do with a normal smart lock, you still have to turn the handle.

Includes a magnetic door sensor

The Nuki comes with a small square magnet that you can stick next to the lock (on the door frame) that acts as a standard contact sensor. This allows the Nuki app to show whether the door is open or closed, but it only seems to work in the app, not through any integrations. If you already have a sensor on your door you could skip it, but if you’re going to use the Nuki app regularly it’s worth sticking it on and running the calibration.

Being able to see the door state can be useful if you’re away from the door after locking it, as you’ll be able to see if it didn’t close properly and is not secure, even though the lock bolt may be extended. This is particularly true because of the ability of the lock to actually open the door remotely.

Multi User Support

Any good smart lock will allow you to create digital keys to give to whoever you want. Nuki makes this very easy, and unlike some others does not require anyone to create an account and password. This is very refreshing, and more secure as well.

The process is simple, you go into the lock settings in the Nuki app and select Manage Users. From here you can create a new user, name it and assign the permissions you want it to have. These allow for remote access (which does require a login to Nuki’s web service), Allow them to lock the door (not just unlock), or limit their access times.

Once you’re ready it creates a code which you can then send to the other person via whatever means your phone allows (text, chat, email, etc). The recipient will be given instructions to download the app, then they can click the link which will open the app and enter the code. That code will set up their access key automatically, and you’re done.

At any time you can change or revoke their access, as it’s handled on the lock side and not on the end users device. You retain control and visibility of who has what access, and it’s clear and simple to manage.

Good range of optional accessories

Nuki installed on my worn out door hardware

Besides the bridge, Nuki has a few other handy accessories. Of interest would be the Fob and the Keypad. The Fob provides for some added convenience by giving you a key ring attached button to unlock the door easily, like a car key remote. The keypad offers a way to enter a PIN to unlock the door similar to some other smart locks.

I’m not such a fan of that though as it offers another attack vector by exposing physical hardware to an intruder. That would require some technical skills, but as with all keypads, wear and dirt can expose potential PIN combinations on the buttons themselves, making guessing the code easier. Sure, it’s a small risk, but the the combination of the fob, the app, and voice control eliminate the need for this in my opinion unless you’re using it in a more communal setting like an office.

As for the bridge, you’ll need it for all use cases apart from HomeKit and local Nuki app use. If you want to control or check your lock away from home using the Nuki app, you’ll need the bridge to provide connectivity over the internet. Similarly, all other integrations will need WiFi (and potentially internet access) to connect, so again the bridge is required.

Security Certified

Nuki has gone to the trouble of having their apps and products certified independently by the AV Test institute, an IT security research group based in Germany. AV Test offer analysis and certification services for various tech categories, Smart Home being one of them.

This is a nice move by Nuki, as we often only have policy statements and good intentions to go on when it comes to the security of connected devices, unless a security researcher has taken an interest. Given the sheer number of products hitting the market this is not very common, unfortunately.

AV Test has checked over the lock and the app and have given them a glowing report in terms of implementation, security best practices, and data privacy. You can see the full report for yourself if you’re interested. Notably, this is the third audit that Nuki has had conducted, so they’re keeping it current as well.

The Verdict

Normally I’d offer up some alternatives that match the use case of a product, but in the case of the Nuki Smart Lock there really aren’t any others that can offer compatibility with these door types and provide the breadth of smart home integration on offer here.

The Nuki lock offers a good smart lock solution for compatible door hardware where you can’t (or don’t want to) replace any of the existing lock. They’ve catered to a wide range of preferences and use cases, and the intelligent calibration allows you to tune things how you want them to work. The optional accessories also provide a great deal of flexibility in how you want to operate your smart lock, although all of these carry quite a price premium.

With independently certified security and privacy implementation you get some peace of mind that’s usually hard to come by with any smart device, but is especially important with locks for obvious reasons.

Bulk, noise level, and price are the key downsides. The bulk of the device probably won’t be an issue in most cases, it’s a little tight for mine, but it doesn’t actually impede use of the door knob. It’s more of an aesthetic caution. It’s worth checking you clearances though before going ahead.

The noise level can be adjusted somewhat through calibration, but is a largely unavoidable aspect of battery powered motor drive devices. The gearing required means extra noise and run time in order to limit battery drain and prevent excessive battery changing.

These minor issues, and the fairly high price point, might put you off, but if you’re in the situation of having the types of door hardware the Nuki is aimed at, it’s a solid choice. I’ll be keeping it installed on my door.