While most smart thermostat manufacturers have opted for a single box, Honeywell has chosen to go down a different direction with Evohome: room-by-room control with smart thermostatic radiator valves (TRVs). While the competition is slowly catching up, Evohome has stayed ahead of the pack with its more comprehensive control. Constant system updates, including Alexa integration and IFTTT support, means that Evohome remains the most powerful smart heating system.
Related: Smart Thermostats in the UK
The reason Evohome is the most expensive smart heating service is because of the design. Prices start from just £250, but this doesn't include installation, which typically costs £100. Evohome works using zones, and each zone requires a TRV that will set you back £59 – plus you can add an optional hot water controller for £70.
In the two-bedroom flat in which I tested the system, a combi boiler meant no hot water control was needed, but I still needed five TRVs (kitchen, living room, hallway, both bedrooms). You can add zones over time, but a complete system still costs north of £650.
The good news is both the TRVs and its dedicated controller look the part. The TRVs replace the mechanical temperature control on your radiators – assuming you even have these – and clearly display the local temperature, their battery life, sync status and a minimalist twist dial that lets you manually adjust the temperature of the radiator to which they're connected.
Build quality is rock solid, although the TRVs do look a little industrial; Tado's Smart Radiator Thermostats look much more modern and slick.
Unique to Evohome is a standalone touchscreen control. This gives the controller real gravitas and does away with the need for buttons altogether. It's battery powered, but charges on a simple stand; a wall-mount kit is available if you'd like to place the controller somewhere more central.
When Evohome was first launched, remote internet controller required a separate Remote Access Gateway – a rather sizeable box that had to plug into your router via an Ethernet port. Fortunately, Honeywell has updated the system, and the new controller has Wi-Fi built in, replacing the need for the Gateway.
Related: Nest vs Hive
Evohome's strength is in the way that it provides individual control over each part of your home, letting you set your heating schedule by zone. Zones can include one or more TRVs: multiple TRVs can be used for multiple radiators in one room, or to group multiple rooms together. I have mine set up to control each room individually.
Honeywell says that its system offers the best savings, since you're only ever heating the areas that you want. For example, you can turn off rooms that you don't often use – or at least set them to a low temperature. You can also control when the heating comes on, so you may want to have the bedroom come on early, and then have the kitchen warm up later, just in time for breakfast.
There's even control over how the heating should work. First, you can have your heating trigger at a set time, much like with a regular heating system. Or, you can set Evohome to learn the thermal properties of your home so that the heating turns on early enough to reach your set temperature by the start time you set.
The downside of this system is that you manually have to configure the schedules for each and every room. Schedules set temperature switch points: effectively, you tell Evohome what temperature you want at each point of the day; there's no real "off".
While this may sound a little complex, both the neat app and controller make configuration straight forward, and you can copy schedules between days (app and controller) and between zones (controller only). I found that it took a few weeks to get the schedule right in every room, tweaking as I went.
The good news is that Evohome includes Quick Actions such as Economy, Away, Day Off and Heating Off, and these can be applied via the controller or the Android and iPhone apps remotely – should you forget to change the system before going on holiday, for example.