Price: £179 inc VAT
Rating: 8

Smart thermostats are hot property right now, with gas suppliers quick to get in on the act and bundle them with certain tariffs to woo prospective customers. We've already reviewed British Gas' Hive system as well as the standalone Tado package. Here we take a look at the Google-owned Nest Learning thermostat. See also: Best smart thermostats 2014: Hive vs Nest vs Tado vs Heat Genius.

Surprisingly, the UK version of the Nest isn't the same hardware that's sold in the US. This explains the delay in the UK launch. Houses in the US use different heating systems, as they're also required to cool as well as heat. In the UK, of course, we've barely any need for air conditioning, being much more concerned with keeping warm. (See also: Heat Genius review.)

Nest Learning Thermostat review: display

The Nest stands out because of its circular colour LCD display, which makes it a gadget you'll want to show off rather than hide away as with the Hive. Because there's a display, you don't need to launch a smartphone app to change the temperature, yet the kit is no more expensive than others which omit a screen.

The stand was developed especially for the UK, but it's not included in the box - it'll cost you an extra £29. However, while the stand might be useful in some cases, most people should be able to use their existing in-wall thermostat wiring to power the Nest's screen. The kit even includes a big plastic plate to cover up the old wallpaper, paint or holes you find when your installer removes your old thermostat. That's because the display is much smaller than you expect, measuring just 83mm wide.

The display itself is has a 44mm diameter and a resolution of 320x320 pixels (the same as the latest Android Wear smartwatches). Viewing angles are good left to right, but not when viewed from below. That means if your old thermostat was mounted quite high up on the wall, contrast is not all it could be.

There's a rotating dial surrounding the display which oozes quality. It doesn't click: the sound you hear is actually coming from the speaker inside the device. The whole unit can be pushed to select options (and enter the menu), but all the settings can also be made from the free app, which is available for iOS and Android. There's no official Windows Phone app yet, but you can check and adjust settings from the Nest website, where you can also view energy reports.

A hidden sensor below the display detects movement and automatically turns the screen on when you walk past or raise your hand to use the dial. Another sensor detects if the sun is shining on the display and ensures it doesn't play havoc with the internal thermometer, which would otherwise signal that it's time to turn the boiler off.

Nest Learning Thermostat review: Heat Link

The other gadget in the box is the Heat Link. This attaches to your boiler, and has built-in Wi-Fi to connect the system to the internet via your wireless router. Virtually every other smart thermostat has a third component which connects to an Ethernet port on your router, so this is a much neater solution if your Wi-Fi coverage is good enough.

The Heat Link has a button which can be used to put the Nest into manual mode, just in case you need it. Holding it for ten seconds resets everything.

Nest highly recommends you have the system professionally installed because of the high voltages involved. However, if you're comfortable changing a light switch, you'll have no problems installing Nest.

The Heat Link is compatible with the vast majority of heating systems, including combi-boilers, those with hot water tanks, underfloor systems, air source and ground source heat pumps and others. You can check Nest's website to see if your system is compatible.

Nest Learning Thermostat review: How it works

At its most basic level, you can use the Nest just like a dumb, old thermostat. You can walk up to it, turn up the heat and sit down again. If it's too hot, you can turn it down a bit.

Of course, it's a lot smarter than this, and you'll probably find you won't need to touch the dial (or app) much once the system has learned your schedule. This is where the learning part comes in. For the first week or two after installation, you're encouraged to turn the dial down when you leave the house, and turn it up when you come back in.

Alongside this 'training', the movement sensor detects whether anyone is still in the house. If not, it will turn down the heat automatically, and show Auto AWAY on the display. Pets won't set off the sensor, so you won't end up wasting gas by heating the house up for your cats.

It should go without saying, but we will anyway, that you can control the temperature from anywhere using the app. As long as you have an internet connection, you can change settings and turn down the heat remotely.

The thermostat is also a programmer, so you can use the display or app to set a schedule, just as you would a traditional programmer. However, instead of 'on' and 'off' you set the temperature you want your home to be when you're in, and a low temperature for all other times - this is known as a 'setback' temperature.

Thanks to the learning process, the Nest will automatically create a schedule for you, and you can see in the app whether changes in temperature were due to someone operating the dial or an automatic change based on schedule.

In the couple of months we've been testing Nest, the auto-schedule has produced some very odd timings. However, because it has been the summer holidays and no heat has been needed, it's impossible to come to any conclusions about this. It's also not possible to say anything about the effectiveness of the system, including the much vaunted True Radiant feature, until we actually need the heating on. (True Radiant for the uninitiated is Nest jargon for learning how long it takes your home to heat up, and then fires up the boiler at the right time to hit your scheduled temperature.)

We'll update this review when the routine is back to normal and temperatures drop low enough to actually require radiator heat.

You can check on the status of Nest's learning feature by going to the settings in the app or on the website, where each feature will either say 'Ready' or 'Learning'. You can also disable any you don't want, apart from Leaf and Time-To-Temp.

The Leaf appears on the display when you set the dial to an "energy-saving temperature", encouraging you to keep the heat below around 19 degrees.

Nest Learning Thermostat review: Zones

Some rival smart thermostats allow you to control the temperature in different 'zones' around the house. Nest can do this too, but the drawback is that you need one Nest thermostat for each zone - not a cost-effective option for most people.

HeatGenius, for example, offers smart TRVs (thermostatic radiator valves) which allows you to control the temperature in the most important rooms.

With a single Nest thermostat, you're reliant on any existing 'dumb' TRVs to shut off radiators when the set temperature is reached. For most normal-sized homes this works well enough, and means you're still saving money compared to the £50 or so you'd spend on each smart TRV on a system such as HeatGenius. If your home has 10 radiators, it will take quite a few years before you start saving any money due to the high initial outlay.

Bear in mind that you can only use multiple Nest thermostats in a home which has a heating system which can heat different zones individually. Older homes with a conventional gas boiler typically heat the entire house, and unless the pipework is physically changed to include two or more valves for different zones (upstairs and downstairs, for example) then adding extra thermostats is pointless.

Nest Learning Thermostat review: Nest Protect

As well as controlling heating, the Nest system also integrates with the Nest Protect smoke and carbon monoxide detectors. These are available as mains- or battery powered versions, each costing a hefty £89.

However, these are much smarter than traditional alarms as they have vocal warnings instead of meaningless beeps. For example, if you have multiple Protects installed, you might hear a warning "Be aware. There's smoke in the living room", giving you an early heads-up of a potential problem.

If there's a lot of smoke or carbon monoxide, an alarm will sound, along with "Emergency! There's smoke in the living room," helping you to decide on the best exit route in the event of a fire.

The integration also means you'll get a notification on your smartphone or tablet to warn you of low battery power, or that an alarm has gone off - useful if you're away from home.

Another benefit of installing one or more Nest Protect is that it detects motion so the thermostat has a better idea of whether anyone is at home or not. In turn this helps to ensure Auto Away is more effective.

Nest Learning Thermostat review: Software version 4.3 update

Since launching the Nest in the UK, there have been a couple of minor software updates, but over the next week or two, a much bigger update will roll out.

It includes three new features: Enhanced Auto-Schedule, Quick View and System Test.

Nest has refined the algorithm for determining an automatic schedule, and claims this could bring up to 6 percent extra savings. This is the third version of the algorithm which has a better understanding of how long your home takes to heat, and slightly reduces the time until the system switches to Auto Away. Enhanced Auto-Schedule "learns all the time and reacts quicker to changes in routine", such as school holidays and the Christmas break. We'll update this review when we've been able to see how the algorithm works in practice.

The second feature - Quick View - is much more noticeable since it's a new interface for the settings on the thermostat itself. The main temperature screen remains unchanged, but when you
click it, you'll get a view like this:

This gives you a lot more information at a glance and means you don't having to go into submenus to see information such as yesterday's energy use or the next item on the heating schedule since the text in the centre changes as you rotate the dial. It's also much quicker to turn off the heating now, and easier to see if there's a problem as an exclamation mark appears in the centre of the settings icon if there's a problem.

Finally, System Test has been added to solve two issues. First, the installer can test the system and ensure it's working fine before leaving. It also lets you test the efficiency of your heating system to make sure it's working properly before winter sets in, and hopefully get a heads-up of any potential issues. It works by timing how long it takes to reach a set temperature, and warns if it's too long based on how long it has taken previously.

There are a couple of other minor updates whcih add more time zones and weather information for Eastern Europe and Asia. More relevant for UK users is that error messages will now appear in the iOS and Android app instead of only on the thermostat's display.

Nest Learning Thermostat review: Bottom line

Nest is the only smart thermostat system which also incorporates a smart smoke detector. Does that make it the best choice for you? It’s certainly easy to use and the circular display is a great talking point.

The smoke alarms are on the expensive side, especially if you need two or three to adequately cover your whole house. However, the Nest kit itself – without installation – is good value at £179, and should pay for itself within a couple of years.

Saving money, though, is only one benefit of smart thermostats: the ability to monitor and control your heating remotely is very useful. The only way you’ll get a cheaper smart thermostat is by getting one bundled with a new gas tariff, so on that basis the Nest is good value.

One last thing to bear in mind is that you could buy a system that allows you to control multiple zones cheaply. You could start off with the basic thermostat, and add controllers for other zones later – potentially when funds allow, and this would be cheaper than buying multiple Nest controllers. But for those happy to have just one thermostat and rely on TRVs to control each radiator, the Nest is a fine choice.

Buying Advice

If you need only a single thermostat and don't want control over several zones, the Nest is a good choice. The Nest Protect smoke and carbon monoxide alarm also works with the thermostat, but it's not cheap.