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How to buy the best smart thermostat

By Matt Clear

Use our Which? expert smart thermostat reviews and buying advice to choose the smart thermostat that's right for you and your home.

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Smart thermostats offer a wide range of different features, so deciding which ones are the most important to you is key to choosing the right smart thermostat for your home. 

Watch our video guide above, to find out what you need to consider when buying a smart thermostat. 

You can compare smart thermostats and find the right one for your home - go to our smart thermostat reviews. 

Hot water control

Some smart thermostats can be used to control your hot water, as well as your central heating. If you have a combination boiler which provides hot water instantly when you turn on the hot tap or the shower, then obviously you won't need a smart thermostat that does this.

Not all smart thermostats with hot water control include it as standard - some charge you extra for it. 

Being able to use an app makes turning on the hot water much more convenient. If you've switched it off because you've had a weekend away, for instance, and fancy a nice hot shower when you get back, simply use your smart phone to turn it on again before you get home. 

As with a traditional thermostat, you can also program a schedule so you don't have to suffer a cold shower because you forgot to put the hot water on. The difference is you can use your phone, or some cases your computer, to do it. 

Multi-room control

Some smart thermostats let you set different temperatures in different parts of your home from the same smartphone app. This would be particularly useful if you have a larger home, and where parts of it often are not being used while people are in other areas.

So if you usually watch TV in the evening, you can keep your living nice and cosy while you turn the heating down or even off in any rooms you're not using. 

To use this feature, you'll have to buy either an extra thermostat or another device for each area you want to use different settings for - so with two thermostats you could have different settings upstairs and downstairs. The extra thermostats or other devices aren't always cheap, though - some cost as much as the first thermostat you buy - so you'll need to weigh that cost against the potential energy bill savings you could make by not heating parts of your house which don't need heating.

Typically, though you'll need an existing multi-zone heating system to be able to do this. The Honeywell Evohome is the only smart thermostat we've tested which allows you to control different areas of your home without a multi-zone heating system.


Some smart thermostats claim to be able to learn your routine and preferred temperatures, and program themselves accordingly. 

This saves you the trouble of having to program a schedule yourself, but it does reduce the amount of control you have over your heating. 

However, learning functions can be turned off. So if you don't like the schedule the smart thermostat has come up with, you can switch back to manual control and program it yourself.


Smart thermostats with a weather-responsive function can adjust the internal temperature according to the weather forecast and the temperature outside. 

So if a cold snap is on the way or the sun is about to come out, the thermostat can adjust your temperature settings to reflect the fact that the temperature is about to change.

Motion sensors and GPS tracking

The purpose of both of these features is to detect when you enter and leave your home and adjust your heat settings accordingly. Turning the heating down when you've left, and pre-heating your home when you're on your way back so that it's at the right temperature for when you open your front door.

The Hive's geolocation feature works slightly differently - it alerts you when you’ve left the heating on and you’re away from home, or when you’re coming back and the temperature’s set lower than you’d like. But it won’t adjust the settings automatically.

This feature is most useful if you're in and out of the house at irregular times - as otherwise, you can just rely on the schedule to turn the heating off when you leave and back on in time for your return home.

Check out our smart thermostat reviews to find out which smart thermostats have the features we've talked about here.


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