The belligerent can ignore this, but having seen the install – which takes about an hour – I can’t argue with Honeywell’s logic.
The good news for those building their own systems is that fitting a TRV simply involves unscrewing an existing radiator thermostat, screwing in the TRV, and syncing is simply a matter of a button press. As a result, expanding the system can be done easily and will allow users to spread the cost over time.
In addition to the TRVs, the Evohome also requires a wireless relay to turn your boiler on and off. You'll need a second relay if you want to operate a secondary hot water heating system.
So how does it all come together? As you might expect, at first the going is slow – but the experience improves rapidly thereafter.
The reason for this is down to the user. Quite simply, it's hard work trying to break down your heating schedule. What do you need on a Saturday at 11am versus 3pm? Can you turn the heating down from 7pm until 9pm on Tuesdays while you’re on a course, or is that only every second Tuesday? The combinations are endless.
Consequently, I found that you'll adjust your basic schedule regularly before settling on one that works for you and your household. Since you tend to then leave the system alone, it's also easy to forget to set quick actions such as "Heating Off" when you go away, or to turn it back on when you return. The Tado and Nest systems do this better, although Honeywell's IFTTT channel at least means that you can ape these features.
That said, the Evohome is a far more powerful system than any of its rivals because of its sheer level of control. There's great satisfaction sitting in the living room in the evening at the ideal temperature, while seeing that the rest of house is off but knowing each room will be the right temperature when you need it. Then, when it's time for bed, the bedroom is perfect and the rest of the house will cool.
Manual control is extremely advanced, too. You can set a temperature from the controller or app, with a choice of whether you want the change to be permanent or to last until a set time – the default time is the next switch point. Changing the temperature from the TRV defaults to the mode set by the app or controller.
Evohome's TRVs are also the most intelligent I've reviewed, with a built-in window mode. Open a window, and the TRVs measure the temperature drop automatically, and then switch off the heating. It works really well and means that you're not wasting resources trying to heat the outside as well.
With time this makes other systems and their heating on/off approach feel crude by comparison. Zoning is quite simply more efficient, and it was clear the boiler was switching on less often and for less time when it did.
The mobile apps are also smart, stable and well designed. Honeywell has clearly arranged the app so that it's clear to see, at a glance, your entire home's status. In comparison, Tado's app makes multiple zones rather more clumsy to control.
Grumbles? I do have some.The controller’s colour touchscreen is a resistive rather than capacitive panel in the way of modern smartphones, so it's occasionally slow to react. It also doesn’t offer great battery life, lasting about an hour unplugged before low battery beeps begin – and the battery indicator doesn’t always reflect this.
By contrast, the TRVs last 2.5 years on their batteries, which are then easily swapped. However, they do need to adjust their valves once per day to keep them loose, and this fairly quiet and short noise – a few seconds – can catch you off guard. Following a few weeks, I tuned the noise out.
TRVs can occasionally report the wrong room temperature, particularly if they're installed in an enclosed space or behind furniture. There are a few ways round this problem.You can use the offset feature of the TRV to change the reported temperature (+/-3C). Or you can instead use the controller or a separate Honeywell wireless thermostat to measure temperature in a room.
I had few problems with my installation and only had to use the controller as a sensor in the living room, due to the TRV being behind a sofa.
Honeywell was one of the first manufacturers to add IFTTT support, letting the Evohome interact with other smart home devices. Currently, the system has no Triggers and only Actions: turn hot water on or off, enable or disable a Quick Action, or set a Zone temperature. Still, it means that you can turn your heating on and off automatically, by using IFTTT's location service. For houses with more than one occupant, you'll need to use a third-party IFTTT tracking service, such as Life360.
An Alexa Skill lets you control Evohome using an Amazon Echo. When the Skill first launched, temperature changes were handled rather randomly, lasting until a seemingly random time later. Fortunately, this has been fixed and now changes made through Alexa either last until the next switch point or permanently if the room has been set like this.
Apple HomeKit support isn't available, and it doesn't appear to be on the horizon, given that the change would require new hardware with a built-in encryption kit.
The bigger question probably concerns whether you're prepared to pay the amount required for the Honeywell Evohome? Logic would suggest the larger the home and the more TRVs required, the more likely that person is to be able to afford them – but, obviously, that isn’t always the case. And for those with older central heating systems without temperature controlling valves already installed, the cost and hassle of upgrading is significant.
Personally, we’d like to see either a reduction in their price or a couple of TRVs bundled to get users up and running, as supplying the controller and gateway without any makes the pricing deceptive.
Then again, if you're prepared to invest in the Evohome, it is without doubt the most comprehensive and accurate system I've seen – plus it can be expanded slowly for those who can’t afford everything up-front.
As for the savings, it will require a full calendar year to weigh up all the benefits, but there's no doubt that being able to control your temperature automatically room-by-room, day-by-day and hour-by-hour makes more sense than an everything on/off system.
The bigger the home, the more the up-front outlay, but also the faster you should see a return on your investment. Honeywell claims the Evohome will have paid for itself within 2.5 years and – your individual tariff aside – I see no reason to doubt that.
The Honeywell Evohome is the Rolls Royce of smart thermostats, but that metaphor applies to cost as well as performance. Small flats can expect to pay around £500 and bigger homes around £1,000, but if you can stomach the cost then you're buying a far more advanced system than the on/off alternatives from the likes of Nest, Tado and Hive – and it should recover its costs more quickly.
Even when you kit out Tado with Smart Radiator Thermostats, Evohome has the edge, since its app and controller are better designed for multiple zones, and its TRVs are more intelligent. The mass appeal of Nest, in particular, is unlikely to be dented by Honeywell, but Evohome owners will feel rightfully smug.
Related: Nest Protect Review