Despite this, it’s come up with a brilliant product that does exactly what most people want from a smart heating system, primarily the ability to control temperatures in individual rooms and only heat those you want to heat. That’s in contrast to the Nest Learning Thermostat – and others – which use a single thermostat and heat all rooms based on the temperature at a single point in your home. WundaSmart isn’t the first smart heating system to provide room-level control – and kitting out your rooms will cost you a pretty penny – but in the long run it will undoubtedly save you money. And with energy prices rocketing, this approach is really starting to make a lot more sense than it used to.
Features
Uses separate thermostat to TRVs for accurate readingsNo data stored in cloudWorks if internet connection drops out
If you go for the most basic WundaSmart Starter Kit, which costs £199.99, you get a thermostat with a monochrome display, a smart TRV for one of your radiators and the HubSwitch which connects to your boiler. This compares reasonably well with the Nest, Hive and other thermostats. But if you’re going to choose WundaSmart over the single-thermostat systems, you’ll want considerably more kit than that. In order to control the temperature in specific rooms, you’ll need a smart Radiator Head for each radiator in those rooms, and one thermostat per room. That’s because – sensibly – WundaSmart doesn’t record the temperature at the Radiator Head. Instead, it uses a combination of that temperature and the one measured by the room thermostat for a more accurate reading of how warm the room is. You have a choice of two thermostats. You can go for the same thermostat as in the Starter Kit (£70) or a screenless version (below) for £50. The latter has no buttons so isn’t used for control: only measurement. It also has terminals for an optional floor probe if you want to measure the floor temperature. Both thermostats measure humidity as well. Although the app allows you to choose two different types of Radiator heads when adding them to a room, only one type is sold: the one with buttons. This, unlike many rival smart TRVs, has no display so it isn’t possible to see what temperature you are setting when using the + or – buttons. This is a shame considering they aren’t cheaper than those rivals, but guests can at least increase or decrease the temperature without needing to ask the homeowner to adjust it in the app. Any changes last for two hours, unless they’re overridden by a change from another source: the app or your existing heating schedule. The system supports up to 50 radiators and 30 rooms, which is plenty for homes and more than competing systems. It’s also partly aimed at office use, where those high numbers could come in handy. As you’d expect, there’s also support for under-floor heating and a controller unit costs £99.95.
Schedules and geo-fencing
You can set up heating schedules in the app, per room, and there’s the option to use ‘adaptive startup’ which, instead of starting heating at the times you’ve chosen, the system will learn how long a room takes to reach temperature and will pre-heat to get it to that temperature by the times you’ve set. You can use geo-fencing so that heating is turned off and on based on whether or not someone is at home. This avoids heating specific rooms when no-one is in them. There are lots of options here, and you can set different rules for each room. You can register multiple phones so that, for example, when a teenager leaves the house, heating in their room is turned off. For communal rooms like the kitchen and lounge, you can choose what happens when the last registered user leaves, including “Set off until first User returns”. In other words, don’t heat the kitchen until one of the family members returns home. There are also choices for what happens when someone is back home: resume the heating schedule, go to Eco mode until the next scheduled heating period or set the Comfort mode until the next scheduled heating period. Setting up geo-fencing can be quite confusing. First you need to register phones: otherwise the user list is empty and there’s no option there to add anyone. When registering, you can choose how far from home you need to be before you’re seen as “home” or “away” – the default is 0.3km. Once set up, it works very reliably.
Modes and options
Near the top of the Home screen is Quick Switch. This allows you to override your schedule and change the temperature in all (controlled) rooms to Comfort, Eco, Reduced or Off. You can choose a temperature for each mode, so you have full control over what each does. Plus, after choosing a mode, you then pick whether it will apply until the next change in the schedule or until someone manually changes the temperature. Along similar lines is the Boost function. A bit like Hive’s similar feature, there are two buttons on the HubSwitch marked Boost 1 and Boost 2. In the app you can set what these do, which means choosing which rooms to heat and for how long. Then, when you press one of the buttons, those specific rooms will get heated to the Comfort temperature. You’ll just have to remember which rooms each button controls if you’ve set each differently. Oddly, there are no virtual Boost buttons in the app which is a bit frustrating if, like mine, your HubSwitch isn’t easy or quick to access. Energy-saving options include open-window detection. This needs to be enabled for each room and will spot a temperature drop and automatically turn off radiators if it thinks a window has been opened. You can choose how much of a drop there needs to be (measured over two minutes) to activate this mode and how long to stop heating for. Another is Holiday Mode which is buried deep in the settings and offers no explanation of what it does. You can set start and stop dates, but there’s a separate setting to turn Holiday Mode on and off manually. Looking to the user manual, it “pauses your heating and hot water schedules until the end date. It will revert to antifreeze settings. If for any reason you want to turn on your heating or hot water during a holiday period, you can boost either for a period of time using the app.” If you’re concerned about installing a wireless system, which this is, into a large home or period property with thick walls, the good news is that the radio “Seeker Signal” that WundaSmart uses offers a bigger range than Zigbee or Z-Wave – two commonly used alternatives. I certainly had no issues, even though my boiler – situated at the very back of the house – was over 50 feet away from the radiator heads at the front, with quite a few walls in the way. It’s so confident it will work in homes of any size or construction it doesn’t offer repeaters: it simply doesn’t need to. The final feature of note is that none of your data is stored in the cloud. WundaSmart opts instead for storing that data locally, encrypted, “in your system”. This also means that it will continue to work even if your internet connection goes down. But, naturally, you wouldn’t be able to control it remotely if that happened.
Installation
Professional installation recommendedDIY installation possible
For this review, and in order that I could properly test how a full system works, WundaSmart shipped over enough thermostats and radiator heads so that every room could be controlled independently. The only room I couldn’t use it in was the bathroom which had a towel radiator with no TRV. Theoretically, it would be possible to fit a valve, but this would require a plumber and more expense. As there’s no under-floor heating, I couldn’t test the Connection Box. Before you order radiator heads, it’s worth checking that your TRVs are all working properly, and are compatible with them. This isn’t a case of seeing if the existing TRV head turns ok: it must be removed and the pin beneath pushed to check it moves up and down smoothly. If not, and stuck-open valves are fairly common, you’ll need to try and fix them or have them replaced by a plumber. The Smart Radiator Heads will fit standard M30 x 1.5 TRV bodies, and it’s simply a case of unscrewing the old head and replacing it. WundaSmart will also supply plastic adapters for most other common types (on request) so you can still install the smart ones. I found around half my home’s radiators had the older M28 thread, but installing adapters took mere seconds: the kit includes various lengths of plastic pins so you can choose the one that fits best. There’s no option to pay for professional installation when you order, so while WundaSmart recommends this, you’ll need to arrange a fitter yourself. As the HubSwitch will attach to the common UK thermostat backplate, it is fairly simple to replace a traditional, dumb thermostat. However, if you do this, you’ll still need to check the wiring is correct to avoid damaging the HubSwitch. Plus, there are dip switches which need to set correctly for your heating setup, otherwise the system won’t work properly or at all. Like the radiator heads, the room thermostats are designed for DIY installation. Screws and wall plugs are provided, but no adhesive strips if you wanted to avoid drilling holes. The app guides you through the process of adding a thermostat and radiator heads, making the process even simpler. However, the instructions aren’t foolproof: it took me a few attempts to figure out whether it was asking me to press and hold a button to put each device into pairing mode, or just press and release, or press twice. Hopefully WundaSmart can update the app so there’s no ambiguity. Once paired, I had no issues with connectivity apart from with two screenless thermostats going offline almost immediately. The problem turned out to be that one of the two batteries had fallen out of place, presumably when slotting the unit onto its backplate on the wall. WundaSmart is now aware of this and will – again – hopefully install a foam strip to keep the batteries firmly in place.
Performance
When I originally wrote this review it was July, precisely the wrong time of year to test a heating system in the UK. But I’ve now spent a good few weeks evaluating it in winter. The good news is that it works very well, living up to the promise of being able to control room temperatures individually. Not only that: it largely manages to keep the temperature you’ve set very accurately, and you can see graphs of temperature and humidity, plus when the heating was on in that room, over the past week. For the most part it is utterly reliable, too. There were only a couple of problems which the tech support team dealt with efficiently over email, with replies arriving relatively swiftly. There’s a phone number as well if you need more immediate support during office hours. The issues appeared to be related to the RF signal, and caused the farthest radiators from the HubSwitch (around 60 feet away with several walls between them) to either turn on when they should have been off, or remain off when they should have been on. The former was in fact cured by increasing the ‘downforce’ for that radiator head in the app, which exerts more pressure on the valve pin, ensuring it turns off and stays off. The latter only happened twice and was resolved when the support team ran a recalibration at their end. Dig into the room settings and you can see the rough signal strength for each thermostat and radiator head. I’m told that even the lowest report signal is still enough. Unlike a single thermostat system where you can walk up to it and adjust the temperature, it’s more efficient to set up schedules with WundaSmart. The interface for this is quite confusing at first, until you realise that the temperature (or Off) you’ve selected for that period is displayed above in smaller text, rather than highlighting the setting you just tapped on. Adding multiple heating periods is easy, and you can set different temperatures for each if you want. You can then quickly copy that day’s schedule to other days, and other rooms, and edit them to remove heating periods, durations or temperatures. The manual alternative means opening the app and tapping on each room individually to selecting a temperature and how long to heat that room for. This is easier if you only want to heat a couple of rooms. There’s also the Quick Switch button at the top for setting all rooms to Eco, Reduced, Comfort or Off which can be useful, but is essentially the same thing as adjusting the temperature on a single thermostat system. Compared to the Nest Learning Thermostat I was using before WundaSmart, I also found the information shown by the thermostats (with screens) to be rather basic. They show the current temperature, but you have to press a button to see the ‘setpoint’, which is the temperature the room is being heated to or, as shown above, that it’s currently off. There’s nothing to tell you at a glance whether the heating is currently on or not, and the E-Ink screens suffer from ‘ghosting’ which you can also see in the photo above where the temperature and humidity is still faintly visible. You use the + and – buttons to adjust the temperature you want, which is good for guests who won’t have the app, and family members who don’t want to use it. The same cannot be said about the radiator heads. Without displays, you’re left with only + and – buttons. Although it should be obvious that + increases temperature and – decreases it, the fact they display blue, green or red is confusing to anyone that doesn’t understand these relate to the Reduced, Eco and Comfort settings, and what temperatures those modes are set to. Put simply, I’d prefer it if they had displays like most rival smart TRVs. The motors in the smart TRVs are relatively quiet, making less noise than those in the Honeywell EvoHome system. It’s worth knowing that WundaSmart recommends you keep all internal doors closed for the system to work efficiently. Otherwise, the heat from one room could escape to a room or area you don’t want to heat. That won’t be practical for many living spaces – and impossible for open plan homes – but the advice does make sense. The worst way to use the system, then, is to leave all the doors open and ask just one radiator to heat one room. The other thing that WundaSmart can do is to control your hot water if, like mine, your heating system includes a separate hot water cylinder. It’s the same process as for central heating to set up a schedule for heating it. As with a lot of smart heating systems, hot water control doesn’t feel particularly smart. It’s a simple on/off control and there’s no way to see in the app what the temperature of your water is. If you want to know that, you’ll have to look at the cylinder itself, but often they have a basic thermostat that simply determines how hot the water is heated to, but does not show the temperature of the water inside.
Price & availability
WundaSmart is available in the UK, but you can also buy it and use it in any European country. It isn’t available in the US, Canada, Australia or New Zealand. The minimum you’ll need for it to work is the £199.99 Starter Kit, but as mentioned, if you’re only going to buy that, you could instead buy a cheaper single-thermostat kit. It only makes sense if you put smart radiator heads on all your radiators and you should purchase a thermostat for each room you want to control. If that’s too expensive, you should install at least radiator heads (they’ll work without a separate thermostat) on radiators in rooms you don’t want to heat all the time). For this review, five Smart Thermostats were installed and five Screenless Thermostats. Some rooms have two or three small radiators, which meant I needed 14 smart TRVs. Adding the Starter Kit, the total price was £1639.99. However, if you have a total of 10 radiators and decide not to go for separate thermostats, the system will cost you £799.99. It’s worth taking a look at Honeywell’s EvoHome system as well: some components (such as room thermostats and the UFH controller) are more expensive, but others, such as the Smart TRVs, are cheaper, despite having a useful LCD display. Similarly, Heat Genius is another worthy rival. It goes beyond WundaSmart, allowing you to add other smart devices such as plugs and motion sensors to the system. It can also monitor hot water temperature, which WundaSmart cannot. Heat Genius even offers a colour-matching service for radiator heads, which have LCD displays. It is, however, even more expensive than WundaSmart. A cheaper option is Drayton’s Wiser system, which uses smart TRVs for room-level control. The benefit with all these modular systems is that you can add to them over time. If you can’t afford an initial £1000+ outlay, you can begin with a starter kit and go from there when funds allow. For more alternatives, read our roundup of the best smart heating systems.
Verdict
WundaSmart may not be perfect but it is an impressive smart heating system that’s relatively easy to install and use. You could, if you’re competent, install the HubSwitch yourself, too. The app could do with some finessing, particularly the pairing instructions, the screen for setting up each heating period, and it would be nice to have some virtual Boost buttons to avoid having to go to your boiler. The screenless thermostats need special attention to make sure you don’t knock the batteries out of place while installing them. Of course, the big question for many people considering such a system is how much it will save them on their energy bill. If you have no desire to save money, then you’d have to question the value of paying so much to control individual radiators and rooms. WundaSmart quotes “up to 31%” savings, which is similar to rival systems. It’s almost impossible to calculate exactly how much you’d save because so many factors are involved, not least the fact that the weather is never identical from one year to the next. You can only use typical figures. However, the fact that this system allows you to heat only the rooms you want to at the times you want them to be warm could well lead to significant savings over the next few years as energy prices continue to rise. You can find out more on WundaSmart’s website about whether turning off radiators really does save money. Of course, you could go round your home turning radiators on and off manually throughout the day for free. But let’s face it, no-one wants to do that. Jim has been testing and reviewing products for over 20 years. His main beats include VPN services and antivirus. He also covers smart home tech, mesh Wi-Fi and electric bikes.
