Nest Protect (2nd gen) full review

Nest is best known for its smart thermostat, but as well as controlling heating, the company also makes a smart smoke alarm and carbon monoxide detector, the Nest Protect.

It's now on its second generation (which is slightly slimmer and curvier) and there are two versions available: mains- or battery powered. However, unless you're replacing existing mains versions, it's easier to install the battery model, as the batteries (and both versions of the alarm) are said to be good for 10 years. That's three years longer than the first-gen model.

Nest Protect: Price

A standard smoke alarm will set you back between £5 and £30 and a separate Carbon Monoxide detector around £15-20. This makes the £89 Nest Protect seem rather expensive, even if it is 'smart'. You won't really find discounts online, either. Even Amazon sells it for the £89 list price.

However, there are a few features that make the Protect a lot nicer than a bog-standard alarm, and one could be enough to persuade you to hand over the money.

See also: Best smart heating systems

Nest Protect: Design

It comes in just one colour, off-white, but as far as ceiling-mounted alarms go, it's one of the best looking.

Nest Protect 2nd gen review

It also feels like one of the best made and the neat packaging and high-quality screws help to reassure you the Protect was worth the money.

Installation is easy as the screws will self-tap into plasterboard and hold the plastic quick-release plate in place. There are even diagrams on the plate to help make sure you install it the right way up, and a label reminds you to configure the Protect before fitting it to the ceiling.

Nest Protect 2nd gen review

In the Nest app you can scan the QR code on the alarm and it's a simple process of choosing your Wi-Fi network and entering the password. If you have other Nest product, you may even get away with using their existing credentials.

The Protect is much smarter than a traditional alarm as it has vocal warnings instead of meaningless beeps. For example, you might hear a (calm) warning "Be aware. There's smoke in the kitchen", giving you an early heads-up of a potential problem.

The location information is especially handy if you have multiple Protects installed, as you'll know where the problem is simply by listening. All Protects will go off if one detects a problem, too.

You can easily silence an alarm by pressing the button on the device, or via the app. The latter is a newer feature that's not supported on the first-generation Nest Protect.

Following a Heads-up notification, if there's a lot of smoke or carbon monoxide an actual alarm will sound, along with "Emergency! There's smoke in the kitchen," helping you to decide on the best exit route in the event of a fire.

You'll also get a notification on your phone or tablet to warn that an alarm has gone off, which is very useful if you're away from home and can potentially call the emergency services.

A side benefit of installing one or more Nest Protects is that they can detect motion. This helps the Nest thermostat know whether anyone is at home or not and makes the Auto-Away mode is more effective, turning off your heating sooner if you leave it on and go out.

Also, the integration means that if the carbon monoxide alarm goes off and the heating is on, the thermostat will automatically turn the boiler off.

And if you happen to also have a Nest Cam, this will start recording so you can check what's happening if you're not at home.

There are more features, too. One is a useful night light. Here, the LED ring glows white to illuminate the area for a few seconds when someone walks below the Protect in the dark. It gives just enough light to help you find your way. With mains-powered versions, you can set it to off, on or always on (at night), and with both there's a choice of brightness: low, medium or high. Obviously, choosing 'high' will mean the batteries run out faster. 

Nest Protect 2nd gen review

The alarm will also self-test once a month (and usually when it detects no-one is around), and you'll get a monthly email report of activity.

Finally, there's the 'Nightly Promise' which shows the alarm's status when you turn the lights off at night. If everything is ok, it will glow green so you can head to bed knowing that the sensors are working and that the battery level is ok (you get low-battery warnings via the app, not by annoying chirping while you're trying to sleep).

Compared to the first-gen Protect, the newer model gives fewer false alarms, and this reviewer has experienced only a couple. Not from steam (there's a humidity sensor) but from frying bacon, which the Protect didn't like.

To be fair, I've never owned a smoke alarm that didn't go off when frying bacon or burning toast, and I'd rather the odd false alarm than no alarm when there really is a fire. The Protect - as well as sensing CO - also has a so-called split-spectrum sensor for smoke.

In essence, this means it can detect both smouldering fires (slow burners) and flaming, fast-moving fires.

This is what allows it to give the initial heads-up warning before a raging fire prevents you from escaping.  


Nest Protect (2nd gen): Specs

  • Six long-life AA batteries
  • Split-Spectrum Sensor
  • 10-year electrochemical carbon monoxide sensor
  • Heat sensor, ± 1ºC (± 1.8ºF)
  • Humidity sensor, ± 3% RH
  • Occupancy sensor, 120º field of view to 20 feet
  • Ambient light sensor
  • Omnidirectional microphone, 70 dBA SNR
  • 2-watt speaker
  • Siren: 85 dB SPL at 10 feet (3 m)
  • RGB colour ring with 6 LEDs

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