Time to ditch the front door key? Nest's new wireless smart lock is surprisingly convenient

Convenience

It was a hot day as it turns out. When I returned home, I used the app to unlock the door while walking toward it and the rest of this happened:

• Walked straight into the house
• The alarm turned off
• The inside security camera turned off
• The thermostat turned on, switched to Home mode, and started the air conditioning

All that happened before even walking in the door. It's hard to describe but it similar to the feeling you get when you've had a very long journey – a long flight and cab ride – and finally get home. A sense of peace and relaxation.

Except this time it came from not having to do anything. Not turning things on or off. It all just happened. I didn't even lock the door. As I took the second drag on a cold beer, I heard it close behind me. The next day, the key to the old front door lock came off the keyring.

Now, onto the bad things.

It is battery controlled. It takes four normal AA batteries - which is a good thing because other locks with just two batteries are running out too soon and frustrating people. But it comes at a cost in size.

Like all current smart locks, the part on the inside of the door is a bit bulky. You get used to it quickly, and it's not a monster, but it is noticeable. It is quite a nice design, with smooth edges and so on but even so, you have something much bigger than was there previously – convenience comes with a cost.

Battery empowered

The idea of a battery operated front door lock also doesn't sit very well. It raises the likelihood of something going wrong. Unlike rechargeable batteries, you have no idea how the battery is doing until it starts running low.

As such, there is no way for this reviewer to know how long the batteries are going to last in a real-world scenario. And that is critical. If the batteries need changing every two months, all those conveniences become significantly less valuable.

Ideally the batteries will last at least six months. Better if they last a year. A low-battery warning will appear on both the lock itself and your app when it is nearly done – but that raises another important element: how long do you have before it goes from low battery to no battery?

Ideally, it would be a week. Because sometimes it takes a week to get batteries and install them. Anything less and it will feel like your lock is controlling you rather than the other way around. Or what if you go on holiday for a week and come back to a dead deadlock? We will have to wait and see.

Nest has included a smart solution to avoid the complaints of people being locked outside their own homes with other smart locks: a pair of terminals underneath the lock to which you can connect a 9-Volt battery and give the lock a short-lived boost big enough to open the lock. Then you replace the batteries.

There is one big problem with this, however. Due to the door handle being close to the lock – at least with this reviewer's door – it is extremely difficult to stuff a 9-Volt battery in there.

When we mentioned this safety mechanism on an earlier post, many readers scoffed that you can blow the lock up by running a massive current through it. Which is likely true (we haven't tested). But no more true that anyone's ability to squeeze superglue in an ordinary lock. We did experiment with running electricity of various voltages to the lock to see if it would somehow shock it into opening up. It didn't budge.

Rethink

Taken overall, the most peculiar aspect of using a keyless smart lock on a day-to-day basis has been to question the security of all locks. Once you start digging into it, you realize that if you are determined enough, it's pretty easy to get into anyone's house.

The result of that process has been to strengthen security throughout the house (good luck trying to wedge that window open now). And, having got used to the Nest+Yale smart lock, particularly with the inclusion of the new box strike plate, the reality is that the house is now more secure than it was before.

When you then add in all the conveniences that the lock provides suddenly the idea of shelling out $249 starts to seem like a good idea. Something that actually makes your life a little bit better.

Right now, the only remaining significant concern is what happens to the batteries and how long the device can continue to perform.

If you are a paranoid or security-conscious person you will have already decided that the idea of a smart lock is a horrible, terrible thing. Likewise, it's not a suitable replacement for a serious security system.

But for the vast majority of people with normal door locks this is a smart lock with a purpose. And, so far at least, it has worked flawlessly. The idea of putting technology into the entry point of my own house is the least comfortable I have been with a real-world smart-home review - because it has real-world implications. But, amazingly, that trepidation has given way to satisfaction.

Going back to digging around and fishing out keys will seem like a retrograde step. ®

Updated to add

Nest has got back to us about the battery concerns above. The company says that you will get a first alert about one month before the batteries run out (we said a week minimum would be good). And then a second alert when they need to be replaced imminently.

The lock button on the inside will change color - from white to yellow - when the batteries are low. The app will warn you when the batteries are low and there will also be an audio alert."