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Nest reworks its Thermostat for the UK, on sale today

Google's Nest finally starts selling a tweaked version of its Thermostat outside of the US and Canada.

The new Heat Link box next to the Nest Thermostat and iPhone app Andrew Hoyle/CNET

Nest, the home automation company bought by Google for $3.2 billion, is today releasing its learning thermostat outside of the US and Canada for the first time.

The Nest Thermostat goes on sale in the UK today for $300 or $415 including professional installation. It will also be bundled with some of energy giant Npower's tariffs. The poster child for the growing smart appliances sector, the thermostat is designed to learn the temperature you want your home to be at different times of day and to change it for you.

It contains sensors that detect when people have left the house and whether the sun it out, adjusting your heating accordingly. It connects to the Internet for remote control via a smartphone app and uses all the information it gathers to provide you with a regular energy report to suggest ways of saving money, such as turning the temperature down by 1 degree.

CNET gave the US version of the product five out of five stars, with CNET Reviews Editor-in-Chief Lindsey Turrentine writing , "When a tech journalist pays $250 for a thermostat, you know it's a special kind of thermostat."

UK and US differences

It's taken Nest over two years to sell this product outside of the US and Canada. That delay is due to the differences between the heating systems the countries use, explained Lionel Paillet, Nest's general manager for Europe, in a briefing to CNET. Unlike the "forced air" systems widely employed in the US, Paillet said, the UK employs "radiant" systems, which in Britain mostly means gas boilers heating water to run through pipes and into radiators. In Britain, heating systems use high voltage (in the US, it's low voltage), and the regulations are different.

Nest's solution to is to bundle another box, which it calls the "Heat Link." This attaches to the boiler, replacing the programmer that typically controls the times the heating turns on and off. This box receives commands from the Thermostat, turning the heating systems on as needed.

Nest is selling a stand so you don't have to wire the Thermostat into the wall Andrew Hoyle/CNET

If a house already has a thermostat fitted, the Nest model replaces what you already have, using the same wires. If, like 40 percent of homes in the UK, you don't have a thermostat already, you don't need to wire the Nest in. A stand is available for $50, which means you can simply plug the Thermostat into a power point somewhere, and it will communicate with the Heat Link box wirelessly.

The software on the Nest Thermostat is mostly the same on the UK as on the US version, although it will probably come as no shock to learn there is no cooling setting. As in the US, Nest says it programs itself after a week or so: all you need to do is make sure it's put in a room where people come and go frequently, and turn the dial up or down if you feel hot or cold.

The Thermostat works out how long it takes your system to heat your house and uses weather-forecast information to light your boiler at the best time. On a mild day, for example, the heating may come on 15 minutes before you get up, whereas on a colder day it could switch on earlier. A green leaf appears on the display whenever the Thermostat thinks you're saving energy, and it talks to Nest's other device, the Protect , shutting off your boiler if that detects carbon monoxide emissions.

This unglamorous box replaces your existing boiler programmer Andrew Hoyle/CNET

How to buy and install

It is possible to install the Thermostat yourself in the UK, but Paillet says that in the interests of safety, Nest doesn't recommend it. The company has set up a network of 200 installers across Britain, with each receiving training from the company.

One of the companies Nest is working with is HomeServe. This home emergency and repairs company was fined £30m in February by the UK's Financial Conduct Authority for "serious, systemic and long running failings extending across many key aspects of its business" between 2005 and 2011, including the mis-selling of insurance policies and a failure to investigate complaints properly.

A postcode checker on the Nest Web site will show you which installers are available in your area, and you'll also be able to buy it from John Lewis, Amazon, Apple stores and B&Q. A guide on the site will help you work out if the Thermostat is compatible with your boiler, although Palliet says it will work with almost all the models used in the UK. If you're unsure, you can take a picture of your system and send it to Nest support for advice.

British Gas already has a similar product on sale in the UK for $85 less: the Hive. Palliet says there's no comparison: the Nest's learning features make it much more than a thermostat you control with your smart phone.

Another player in the market is German startup Tado, which uses an app on your phone to figure out when you're likely to arrive at home and turns your boiler on and off at the appropriate times.