Smart Heating Controls - My Experience with Honeywell Evohome - Part 1

Introduction

During lockdown in 2020 it seemed like a good idea to get better control of our heating. My focus was better comfort, but saving energy would also be good. We had Evohome installed in September 2020.

 

So, with the perspective of 3.5 years after installation (Jan 2024), how has the system performed?

 

Note: when I wrote this review it grew and grew...

...I have therefore split it into two: in this post I have attempted a less technical overview and in an upcoming Part 2 I will focus on technical points.

 

What Did Evohome Replace and What Were the Problems

We had a simple dial thermostat in the hall; a 7-day programmable timer in the kitchen with traditional (1-5) Thermostatic Radiator Valves (TRVs) on each radiator:

• The 7-day programmer was a bit of an effort to set up. It was set to go on in the morning and evening during the week and all day at weekends. We hardly ever adjusted this over many years, other than on initial set up.
• We controlled temperature day to day by:
• Adjusting room thermostats (often to maximum or minimum)
• Adjusting the hall thermostat (often by quite big increments to get the 'click' of the contacts to 'kick' the boiler on or off)
• 'Advance' on the timer, eg in the evening, if we were staying up past the time when the timer went off.
• The bathroom was set to be always on (ie if there was hot water flowing to the radiators then the bathroom radiator was on) - it was explained to us by the installer that this was necessary as a pressure release if all the TRVs are off and the boiler is on.

All of this resulted in quite wide swings in temperature, a few household arguments and a few times waking up with a hangover, dehydrated and a really hot house because the heating had been on all night with radiators at maximum, after a late night drinking!

 

Selection & Installation

At the time I read various positive reviews of the Evohome system and it looked to be the only system to give individual radiator control.

 

The Evohome website gave me a local installer who quoted me based on photos of the existing TRVs, so that he could confirm there were no issues in the retrofit:

• 11 rooms/radiators to be fitted with a smart TRV
• 1 x hot water tank thermostat
• The price, with installation, was ~£1800. This included for an Automatic Bypass Valve (ABV) to allow all radiators (including the bathroom) to have Evohome TRVs (see part 2 for more details).

 

Installation was mostly straight forward and took one day; however there were a few gremlins. See part 2 for more details, but these would have been fixed in a couple of weeks / 2 visits by the installer, except that we had a pre-existing wiring fault, that credit to the installer, he tracked down and fixed (at additional cost).

 

By the end of October installation was complete, the system was now working well but our confidence in the Evohome system was low  (especially for my wife who just wanted a working system!) We had seen repeated gremlins and, even excluding the wiring fault, I had to resolve several issues during the first couple of months. Limited online support materials meant that this was somewhat trial and error (ie there may have been very few issues, but perhaps I initially caused more as I learnt how to trouble shoot).

 

Lessons learned:

• Ask the installer how many systems they have installed and if your installation has anything that they have not tackled before or that they see as a problem.
• Get a fixed price and defined scope of work (eg what happens if there are problems). Agree upfront the hourly rate for fixing problems that are outside of this scope. I had done this & so the agreement on extra costs (ie wiring fault) was transparent and there was no argument.
• If there are tricky issues then you need an installer who will stick with it and not give up. I got that in this case, but I am not sure how to judge this other than a sense of if you trust the installer. I think that to my benefit this was a smallish local company and I always got Mike to come and look at problems. I can imagine that  with some (larger) companies you might end up being passed around from person to person.
• I strongly recommend that anyone having Evohome installed takes an interest in the technology and any issues - I ended up learning more about central heating and Evohome than I really wanted to, but this ended up being useful longer term (see below and  part 2). It also gives a lot of materials for a very long blog post!
• Plan on an early summer install. Why? You will have plenty of time to learn the system and resolve issues before you really need Evohome to be 100% functional in winter. In addition, your installer/heating engineer will have better availability and may have lower hourly rates. My September install got into reliable operation just in time for the onset of winter proper (end of Oct), but I had to pay winter rates for some of the additional work.
• After the initial gremlins the system settled down and our confidence grew.
• Evohome has been working pretty smoothly for over 3 years now. Part of this is because when we do get issues (every few months) I have learnt enough to resolve them myself. This is much like other home technology that we have (eg phone, laptop, printer, etc) other than there is less material on YouTube to help.

 

Evohome Software

The software is pretty easy to use:

• Programming a new schedule is reasonably simple. It is much easier than our old 7 day controller.
• There is space for 1 extra schedule.
• The radiator temperature control is intuitive; it overrides the scheduled target temperature and then at the next scheduled temperature change the radiator controller returns to the scheduled target temperature.
• The handset and phone apps have different interfaces. Neither is better or worse just different.

Hand controller scheduling interface	Hand controller temperature override interface
iPhone scheduling interface	iPhone temperature override interface

• There are controls for the entire system (eg for when you go away), but these are limited:
• App 'Eco' mode on: with scheduled switch off time resolution of 1hour - reduces room temp by 3 degrees (but seems to have a bottom limit of about 16degC)
• App Heating On / off: switch on time has one day resolution & this does not turn off the hot water.
• Hot water has to be switched off/on separately from the heating
• The handheld display is different, but not any better.

 

The Evohome software is easy to use and fine for day to day operation - if you are considering buying Evohome do not get put off by the details and recommendations for Honeywell in part 2.

 

Living with Evohome - How we use it:

• We are getting used to switching the heating off when out:
• If we are out of the house for a few hours we tend to use Eco mode as you can set the on time by the hour
• For longer than one day we switch the heating off and try to remember to switch it back on from the phone app several hours before we are home to allow for warm up time. We also have to remember to switch the hot water off/on.
• We have the schedule set to turn off several times in the evening/night, eg 10pm, 11pm and midnight. This allows for those late nights:
• At 10pm the heating goes off (target 5degC)
• If we are staying up we can turn up specific radiators (usually at the radiator)
• These go off again at 11pm...etc.
• This prevents the heating being left on all night, in every room and waking up dehydrated (as well as hung over) as with our pre-Evohome heating control system.
• We have the schedule set to nudge up the temperature in some rooms in the evening; not sure if this is the same for everyone, but 19degC/20degC seems fine in the daytime but cold in the evening.
• We keep lounge cool and use a nice and cosy gas fire. The gas fire is not the most efficient, but has a really nice log effect. My suspicion is that this saves energy (cool lounge for much of the day and in late spring/summer/early autumn we often just use the gas fire and extend the time when the central heating is off completely).
• Battery costs:
• Each TRV (& the hot water thermostat) take 2 x AA batteries
• Very roughly each battery pair lasts 18months
• On our system this is about 24 batteries every 18months or 16 per year
• Amazon price £8-99 for 40 pack of batteries, or around £3.60 per year.
• Central heating service - no change, we still use the same bloke to service the boiler (ie not the Evohome installer) and I do the Evohome (battery replacement + occasional trouble shooting)
• The radiator controller does make a whirring noise when it adjusts the valve. For me this has become a re-assuring 'all is OK' sound. In most rooms the sound level is similar to the boiler firing up (ie not very much). However, it is another reason for not having 'optimum start' configured - at 6am every morning the radiator TRV in our bedroom makes its small whirring sound and the boiler fires up a few seconds later. Often I sleep right through this, but sometimes I am stirring early and I know what time it is; I am not sure that I want this noise varying between, say, 5am and 7am depending on how cold the morning is (but I may still try it).

 

My view of Evohome after 3 Years

• Comfort:
• Consistent and controlled: improved comfort through the day
• Heating not left on all night; waking up dehydrated and hot never happens now.
• To start with my wife hated the faff of learning a new system and teething issues with Evohome (over the 1st couple of months), but after 3 years she now prefers Evohome to our older controller.
• Ease of Use:
• Straight forward. Most day to day operations are:
• Adjust a room thermostat (easy on the app if we are out, but even easier to just change it at the TRV)
  

Adjustment of room temperature using the TRV knob is easy and the temperature automatically returns to schedule at the next scheduled time point.

 

• Turn heating off when we go out and back on before we come home (or using Eco mode to turn it down and then back up)

• Reliability:
• No hardware failures in 3+ years
• After initial 2 months/teething problems, perhaps one fault very 3 or 4 months (mostly resetting a TRV, and one receiver reset) + battery replacement.
• Batteries last 18 months, but each TRV and the hot water thermostat has them, so with 12 sets of batteries I end up changing one set every month or two. The TRV error message for batteries going is clear; it comes up on the handset and gives good early warning. The hot water thermostat battery warning was obscure ("comms fault") and I only discovered that changing the batteries fixed it by trial and error.
• Note battery life on the hand held display is poor. You can take the handset out of its nest for a few minutes (ie the opposite of a mobile phone that needs occasional charging, but spends most time away from the charger).

 

Financial Payback:

Evohome probably saves us some money each year, but the data on money saving, in our house, is mixed up with lifestyle changes (See earlier blog post, eg working at home in the pandemic) and also mixed up with other energy saving measures (eg loft insulation - see future blog post). So the impact of Evohome is hard to measure on its own. I read of 10% savings quoted by others and I can believe that this is true. That would be ~£200/year for us at current energy prices, so a payback of a little under 10 years plus a more comfortable house. I also think that Evohome gives you more control on saving money Vs comfort, ie you have the control to fine tune the savings to be more than the quoted 10%, if you are OK with lower temperatures (in particular rooms/times).

 

Final Thoughts:

• Evohome works well and, for us, is working as promised. My sense is that a complete technophobe might struggle, not in day to day operation, but with the faults that do occur every few months. Reading recent reviews (eg https://www.techradar.com/reviews/honeywell-evohome) it sounds like Evohome is still one of the leading systems and also one of the most user-friendly. If that is the case (& if my system is typical) then my view would be that smart radiator controls are not ready for the mainstream quite yet:
• Better support materials required (3rd party and supplier)
• Better guided fault diagnosis and resolution within the system (eg my 5 year old, low cost, HP printer is great for this)
• Build in more fault tolerance (see part 2 for more on this)
• The length of this article tells you that, from knowing very little about central heating, installing Evohome has taught me more than I ever wanted to know.
• If you are moderately technology savvy (eg comfortable trouble shooting home wifi, printers, laptops, etc) and interested to learn, then you should be fine (I have an Engineering background, but I am sure that this is not necessary). However, if your first response to any technology error is to call someone else then you should anticipate a cold radiator or two, once or twice each winter while you wait for help to arrive! When help does arrive, if this person is technology savvy, but new to Evohome, then the lack of online support materials will be a hindrance.
• Evohome has given us a more comfortable home; we get a more controllable & consistent temperature. My wife was dubious early on, but now likes Evohome purely from a comfort/control viewpoint.