Smart thermostats

We’ve seen some really great discussion on the community about smart thermostats, which has got us thinking. We’re thinking about offering smart thermostats to members to help households reduce their carbon footprint and save on their bills. What does everyone think?

An exciting thinktank called the Behaviour Insights Team has done rigorous research into smart thermostats, and the results are striking. They found that smart thermostats save homes about 6-7% of annual heating-system gas use. For the average home, this means saving £26 a year. And they found that the comfort level was the same, or better, with smart thermostats.

This sounds great to us. We’d love to help our members save energy (and money too). A large proportion of households’ energy is used on heating the home, and it makes sense to use a smart thermostat to control the temperature at a sensible level while conserving energy.

Looking at various smart thermostats on the market, we’re especially excited about Nest and Tado. Do you agree, or are there other models people are excited about? Is there a clear favourite?

Most importantly, we’d love to hear what you think about the idea of Bulb offering a smart thermostat. Is this something you’d like Bulb to offer?

We can’t promise anything yet, but we’d love to try and offer a smart thermostat to our members at a slight discount on their listed retail price. On this note - do you have a preference for buying the product outright, or would you prefer to pay off the thermostat over a period of time (say, 1-2 years)?

Thanks in advance for everyone’s thoughts on these questions.
@“Owen at Bulb” , @“Alistair at Bulb” and @“Andrew at Bulb”

Firstly I’d be interested (in a second one as I already have a Nest)

I think if you can offer them at the same price or slightly cheaper, as an add-on to your bill, they will likely be quite an attractive proposition.
Buying them straight off, unless you can do a really good deal on installation is probably no better than local purchase and installation though.

My preference would probably be for the Nest but that’s mostly because the tado system is more expensive for the same functionality if you require hot water control or want it to be wireless (£199 plus £79 for the extension unit).
If the Tado system was a more competitive price, I’d be interested in trying one out.

However, at your suggested saving of £26/year, it’s still going to take 10 or more years to recoup the cost (Nest plus installation being around £260). The device will also likely have died by then but the tado may fair slightly better in this regard due to its lower display complexity and lack of inbuilt Li-ion battery.
So I stick to my previous comments regarding them not actually saving households any money…
I still don’t know how tado are still getting away with this statement:

Pays for itself in the first year

I’d also worry that Bulb would get stuck with supporting these devices if they did offer them, and that might sound the death knoll for any such scheme as support’s tricky and expensive.

On a related note, I wonder how much embedded energy there is in a smart thermostat and what the whole-lifecycle footprint of the product is.
A couple of old articles and a newer IEEE one:
http://www.lowtechmagazine.com/2009/06/embodied-energy-of-digital-technology.html
lowtechmagazine.com/2008/02/the-right-to-35.html
https://spectrum.ieee.org/energy/environment/your-phone-costs-energyeven-before-you-turn-it-on

Add the datacenter power consumption, the embedded energy of all of the servers and devices required to make these smart thermostats actually operate (no, the data does not go from your thermostat to your phone, it goes across the world and back first), and they’re not actually looking very green at all.

@mowcius

You raise some good points.

For the average UK household, smart thermostats have been shown to save around 4.7% of a yearly household gas bill, rising to 8% for Nest thermostats that utilise their ‘Seasonal Savings’ function. We were being fairly conservative when quoting potential savings in our original post; for the majority of Bulb members, the savings are likely to be higher and this would make smart thermostats a more attractive proposition.

The lifespan of each thermostat is definitely something we’re looking into. We wouldn’t want to recommend a product that wasn’t likely to recover the purchase value before breaking.

Your second point regarding the embedded energy cost of these thermostats is such a good point. It would be interesting to convert this value into the carbon intensity of manufacturing and running the back-end services of a smart thermostat and compare this to the potential carbon savings a thermostat offers when heating your home more efficiently.

Out of interest, what convinced you to go with a smart thermostat?

Out of interest, what convinced you to go with a smart thermostat?
I moved into a new house that had no thermostat at all, so going for a smart one when I replaced the boiler just made sense. The additional cost was not ludicrous (at least not when compared to the cost of the new boiler!).

I really like the idea of getting a smart thermostat via my energy supplier and then paying for the thermostat over a year, or twos, period of time. However, it would be good if the brand/ model of thermostat offered would not only be able to control the central heating and hot water, but also be able to control specific radiators around the home.

I’d certainly welcome a smart thermostat. We’re currently looking at Nest, having ruled out Tado for the increased cost with no additional functionality.

Any idea when this might happen? I take it there are no issues with smart meters and smart thermostats working together? Not really read about that so no idea personally.

I’d certainly welcome a smart thermostat. We’re currently looking at Nest, having ruled out Tado for the increased cost with no additional functionality.

Any idea when this might happen? I take it there are no issues with smart meters and smart thermostats working together? Not really read about that so no idea personally.


Hi @Tomd1984, I really wouldn’t hold your breath on getting a Smart Meter for cheap/free/monthly from Bulb as they’re still currently working on the Smart Meter rollout and a variety of other things no doubt.
As winter is quicky approaching, now might be the ideal time to get one installed though.

Smart meters are however independent of your power meter (smart or otherwise) so there should be no issue with having (or not having) both. The main thing to consider is just that most smart meters require a WiFi signal and a power socket near to the room thermostat part (although there are exceptions to both).

I’d recommend getting a Nest to anyone that’ll listen =)

I got mine from using my Bulb referral credits to cover the cost - with the hope that the Nest would help lower my usage and make the rest of my credits stretch further.

It’s certainly helped lower our useage. And freed me up from over-zealously making timer adjustments.

Having gone from no thermostats, and a timer only on the boiler, I reckon my savings are much more, somewhere in the region of 25-50% less gas used depending on the weather. The nest is also in a more convenient location for setting the temperature. The heating is on far less.

Going from having a thermostat to a smart thermostat will have much smaller cost saving.

This sounds like a fantastic idea. Obv issues around slelcting a brand of smart thermostat could be an issue, as many have various limitations and functions which may or may not meet bulb customer needs.

The offering of the smart thermostat at a discounted prices from Retail is a very attractive idea, I would go a little further by offering it customers on a contractual payment plan. Offer the smart thermostat on contract, like a mobile phone contract, and charge an additional x amount on daily charges and unit price. I am sure many would b happy to pay for the device through an increase in their tariffs.

I’ve just fitted the Wiser system from Drayton. Very affordable and they do a true 3 circuit (DHW and 2 x CH) unit. Their radiator valves can even call for heat. Using room stats and their thermostatic valves you can set up zones to maintain different temperatures in different areas of the home. It’s pretty impressive.

@LancasterLad, I’d not heard of that one before but the TRVs are familiar.

I do wonder how accurately they can guess the temperature of the room though with being so close to the radiator. In an ideal world I suppose the temperature sensor would be located elsewhere, but that’s just another device that needs batteries then.

How long are the batteries in the TRVs supposed to last?

Let us know how you get on with the system over the winter!

I haven’t invested in the TRV’s as yet - just two room stats, one for each CH circuit. More here - https://wiser.draytoncontrols.co.uk/radiator-thermostat

I use the Heatmiser system in my home and have thirteen smart thermostats to control hydronic underfloor heating warmed using a air source heat pump. In programmable mode the thermostats have a learning function which calculates how long (up to five hours) it takes to bring a space to the required temperature. No doubt this is a feature of other systems too.

I personally use the system in non-programmable mode and leave all rooms at a constant temperature of 22 degrees centigrade 24 hours a day. Contrary to popular advice, I find that this gives the best balance of comfort and economy with a heat pump and porcelain tiled floors as the heat source in a very well insulated home. The circulation temperature of the water is 27 to 32 deg C and varies with the weather compensation of the heat pump.

@mowcius I have been reading this thread about thermostats and wonder if you would give me your opinion on my set up here. I am in a very old listed cottage which has a good (I am told) Worcester combi boiler. I can set the times for on/off and each radiator has a 1-5 level of heat, but despite those settings I find the house warm and cold at the wrong times and I am forever adjusting it.

I saw the mention of Nest and have looked at that onliine. Am I right in thinking that if one of those was installed in the living room which is central in the cottage, that it would control temperature better than I am able to now? My broadband router is in the living room. Would I need an electrician or the people who service the boiler to intalll?

I hope you dont mind me asking you. I know you don’t have a crystal ball but I need some understanding before I speak, for example, to the boiler people as they will want a larger sale out of it.

@mowcius I have been reading this thread about thermostats and wonder if you would give me your opinion on my set up here. I am in a very old listed cottage which has a good (I am told) Worcester combi boiler. I can set the times for on/off and each radiator has a 1-5 level of heat, but despite those settings I find the house warm and cold at the wrong times and I am forever adjusting it.

I’m not @mowcius, but the first question I’d ask is do you have any kind of thermostat at all? I know you’ve said you have the thermostatically-controlled valves (TRVs) on the radiators, but do you have a central thermostat?

If not then installing any kind of programmable thermostat at all would be an improvement. It wouldn’t necessarily have to be something fancy like a Nest.

I have an old (11 years) Worcester DT10RF programmable thermostat. I don’t set times I want the system on or off, I set timed temperature targets. The heating is ostensibly “on” 24 hours a day all year round even in summer. The thermostat cycles through 4 different temperature phases each day: a warm phase for the morning, a low phase while we’re out at work, then again warmer in the evening and low overnight. During the summer the house never falls below the temperature set-point and so although the heating is “on” the thermostat never calls for heat and the boiler never fires.

Something like this would solve your problem of the house overheating. But you still need a regular schedule in order for the timed temperature phases to match what you need. If you are home some days and not others, or get up earlier some days and not other, it would be more tricky to prevent unwanted cold times. A learning thermostat like Nest might help with the cold times, but even then it’s not clairvoyant and wouldn’t help on a truly random schedule.

To summarise: A thermostat of some sort is essential to an efficient heating system, but you don’t necessarily need something expensive.

Also to add, your Worcester combi-boiler likely has a timed water pre-heat mode. Typically combi-boilers don’t have timed hot water, because they produce direct hot water on demand rather than heating up a tank full of water. However, some (all?) of the Worcester boilers do have timed water pre-heat, which is a function to keep the boiler heat exchanger warm and so enable hot water to be produced more quickly and reduce the amount of cold water run-off before hot water arrives at the tap.

My old DT10RF has two timers - one on the thermostat for the heating, and another on the boiler unit itself for the hot water pre-heat. It’s not clear to me what happens if I were to install a third-party thermostat such as Nest since presumably this wouldn’t handle the pre-heat function. If you don’t already have a timer for this it might not matter to you. The pre-heat is only useful in the summer in any case, where the boiler isn’t already hot due to running the radiators. However it’s something to bear in mind that you might need a specific Worcester thermostat if this function is important to you.

@Hooloovoo Thank you so much for your detailed response. First can i say I am totally the lay person as far as heating systems are concerned. I am retired, in my 70s, and so do not have an in/out of the house timescale at all.

The boiler is a Worcester Greenstar CDi, no idea how old it is. The control at the side of it is Drayton Lifestyle LP111 which seems to control radiator times only. I believe tap water is heated as I need it and this works well. I do not think there is anything timed to do with hot water. I have Economy 7 so run dishwasher or washing machine at night to benefit from cheaper rates. So I think the answer to your question do I have a central thermostat is No.

What you describe in your paragraph “I have an old (11 years) Worcester DT10RF” is exactly what I was used to previously, and hoped this system would do. The reason I looked at Nest is that it works via WiFi and I thought that would be easier to ‘install’. I am very restricted in what I can do here and cannot just bury wiring behind plasterboard. House dates from 1600 and there is not a smooth straight wall in the place, part of it’s charm of course, and I am lucky to be it’s custodian for now.

It all sounds as complicated as I feared.

What you describe in your paragraph "I have an old (11 years) Worcester DT10RF" is exactly what I was used to previously, and hoped this system would do. The reason I looked at Nest is that it works via WiFi and I thought that would be easier to 'install'. I am very restricted in what I can do here and cannot just bury wiring behind plasterboard. House dates from 1600 and there is not a smooth straight wall in the place, part of it's charm of course, and I am lucky to be it's custodian for now.

You can get wireless thermostats that do not use WiFi, but a different much simpler system. The old DT10RF that I mentioned is one such device, Worcester will have new ones that are designed specifically for your boiler. No matter what you decide to go for, whether it’s a simple wireless device or something that uses WiFi, they’ll both need a receiver to be installed in your boiler by a professional. If you were hoping for something you can just buy and connect yourself, then I’m afraid that’s not the case. Nevertheless there are lots of wireless options that wont require running cable, so don’t let that put you off.

It all sounds as complicated as I feared.

It’s not particularly complicated. It’s just slightly more work than you initially wanted.

Here’s the current range of digital controllers and thermostats from Worcester Bosch:

https://www.worcester-bosch.co.uk/products/boiler-controls#digital

They also appear to have their own Hive-like smart thermostat:

https://www.worcester-bosch.co.uk/products/boiler-controls#smart

NOTE: I’m not endorsing any of these products, I’ve never used them. I was just having a quick look at what Worcester themselves offer today. It’s been a long time since I bought my DT10RF!