How smart thermostats can save you fuel and money

As well as turning off your hot water or boiler as you leave home, some can offer to heat only rooms that need it

With the return to the office in full swing and fuel prices rocketing, smart thermostats offer one relatively easy way to help reduce your energy use without big changes to your central heating system.

These are direct replacements for traditional timers and thermostats that give your boiler a hi-tech upgrade without cancelling out any of its features.

Most work with a large range of gas, LPG, oil or electric boilers, including those with hot water tanks, and many will work with biomass or heat pumps, too.

The majority consist of a control unit that is wired to your boiler and a wired or wireless thermostat that you place in the centre of your home. Many also require a hub that is wired into your router for online or phone-based functions.

Smart thermostats come in all shapes, sizes, prices and capabilities from a range of different manufacturers.

What can a smart thermostat do?

While features vary depending on the model and manufacturer, most give you more control over your heating, hot water and boiler than comes with a standard system.

A thermostat scheduler app
On the Nest app you can create a schedule of when you want the heating to go on and off. Photograph: Samuel Gibbs/The Guardian

You can adjust their temperature setting, set timings and turn the heating on and off via an app on your phone or using Amazon’s Alexa or Google’s Assistant smart speakers. It is a lot easier to create a detailed schedule of when you want the heating to go on and off in an app than it is on the pokey display of a traditional timer but most smart models will also allow you to adjust their schedules directly on the thermostat’s screen.

Some, such as Google’s Nest thermostats, can learn your habits and automatically adjust your heating schedule to save energy when you don’t need it. Many learn how fast your home heats up, too, so they can turn on at the right moment to hit a certain temperature at a set time. The best models also take into account the outside temperature and the impact of the sun on your building, so you don’t end up paying to heat your home when you don’t need to.

Automatically turns off when you leave home

One of the best features of a smart thermostat is the ability to automatically turn off the heating if you are not home. Most can use your phone to track where you are, if you opt in, and can turn the heating off automatically or send you a prompt to do so when you leave home and back on when you return.

Hive heating thermostat being turned down
A Hive heating thermostat.
Photograph: Kay Roxby/Alamy

Some also offer presence-sensing directly on the thermostat – it will detect if anyone walks past it, which helps to avoid the heating turning off if someone is still home even if you are not. Others can be linked to smart door and window sensors, so the heating is turned off if a window is open or you have exited through a door.

Heating history

Another useful feature is the ability to see a history of your heating use during the day, week or month, and to view it in charts comparing your use with the outside temperature. Some allow you to tell it your energy tariff, which allows it to show roughly how much money you have used on heating to help budgeting.

However, some manufacturers, such as Hive, charge a monthly or yearly subscription for access to view your data.

Zonal heating

Some of the smart thermostats can be linked up with smart thermostatic radiator valves to let you control the temperature of individual rooms. They turn each radiator up and down as required and can fire up the boiler when needed.

They promise to increase comfort but also energy efficiency by heating only the rooms that need it. But these smart TRVs are not cheap at £40-60 each and need to be fitted to every radiator, meaning the costs quickly add up.

How much do they cost?

There are lots of smart thermostats to choose from, and most cost between £100 and £200 without professional installation. Hive’s latest Thermostat Mini is one of the cheapest, at £119, including the hub that connects to your router. Installation by Hive costs £100.

Google’s DIY Nest Thermostat E costs £199 or less from third-party retailers for only heating, or the main Nest thermostat for hot water tank control, too, costs £219. Installation costs under £100.

Tado’s wireless Smart Thermostat V3 costs £200, with installation costing under £100.

Make sure to check the compatibility with your central heating system on the thermostat manufacturer’s site if buying for DIY installation.

How do I get one?

Most models can be bought direct from the manufacturer, from online retailers such as Amazon or through DIY shops such as Screwfix and Toolstation. But for people requiring installation, too, many small local and large national heating firms offer the service.

Can they save me fuel and money?

In theory, yes. Google’s Nest estimates that UK customers can save between 8.4 and 16.5% of their heating’s energy use, Tado estimates up to 31%, while Hive says up to £110 worth at pre-crisis prices.

However, in practice it depends on what it replaces, how you use it and how much energy you currently use.

Being able to automatically pause a heating schedule when you leave your home can save considerable amounts of energy if your schedule is unpredictable. Systems that identify when you can turn down the heat and save money without affecting comfort too much can also help.

Simply being aware of the current temperature and heating history can help you save the most money, as turning down the thermostat is still the most effective way of reducing fuel use without modifying your home.


Samuel Gibbs Consumer technology editor

The GuardianTramp

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