Will Smart Raiator Thermostats help reduce my heating bills, are they worth it?

Sterlingtimes

wild666 said:

I have to agree with Dolor STRV's only cost more and offer no more of a saving over TRV's that you can set and forget about. STVR's are, IMO, for those with more money than sense.

That's pretty final given you hold yourself out as having more "sense" than me.

Petriix

wild666 said:

I have to agree with Dolor STRV's only cost more and offer no more of a saving over TRV's that you can set and forget about. STVR's are, IMO, for those with more money than sense.

That's a totally illogical conclusion. 'Set-and-forget' means they're permanently set to be heated to the same temperature whenever the heating is on at all whereas smart TRVs can be programmed to not heat the room while other parts of the house are heated. Demanding less heat objectively uses less fuel and therefore costs less.

Most bedrooms are empty most of the day and only really require heating for a short period before you get up and again before you go to bed. Living rooms are typically used in the evenings while it might just be a home office in use during the day. By heating only the spaces actively in use, fuel bills would definitely be lower.

The manual workarounds are labour intensive. Last winter I effectively created a separate heating zone for the living room and home office (which are joined on one side of the downstairs in Petriix Towers) by lighting the woodburner and turning the gas heating down to 16 degrees on the kitchen/diner side. It saved a chunk of money, but only because I laboriously collected, sawed and dried the wood.

Achieving similar by turning the heating off in the rest of the house while just heating those rooms would have cost slightly more, but saved a huge amount of work. However, I think a better solution would be to have an air to air heat pump (probably multi-split) for both sides of the downstairs which, crucially, would allow separate schedules for heating each zone. Then it's down to persuading people to keep the doors shut... 

BUFF

Petriix said:

wild666 said:

I have to agree with Dolor STRV's only cost more and offer no more of a saving over TRV's that you can set and forget about. STVR's are, IMO, for those with more money than sense.

That's a totally illogical conclusion. 'Set-and-forget' means they're permanently set to be heated to the same temperature whenever the heating is on at all whereas smart TRVs can be programmed to not heat the room while other parts of the house are heated. Demanding less heat objectively uses less fuel and therefore costs less.

Most bedrooms are empty most of the day and only really require heating for a short period before you get up and again before you go to bed. Living rooms are typically used in the evenings while it might just be a home office in use during the day. By heating only the spaces actively in use, fuel bills would definitely be lower.

It's not simple & it's going to vary for every building & user according to their heating system, needs, schedule etc.

Most people will heat bedrooms to a lower temperature than living spaces so even whilst those are still being heated TRVs in bedrooms may have already shut off.
If you take e.g. my house then the condensing boiler can only modulate down to 6kW. None of my rooms take even near 6kW to heat, if I only heat one room or even 2 then the boiler will cycle which is not efficient ...

& then there may be potential long term effects on the building fabric (especially in older, less well insulated properties e.g. interstitial condensation).

As I mentioned earlier the 1 major study that I read put smart TRVs as saving ~3% on average (& massive variation) over a standard TRV but the high cost of smart TRVs (typically ~£50 for the sensor head for the most well know brands/systems & which may also require a hub,  especially if you want to tie in boiler control) means that it can take many years to recover the capital cost of the smart sensor head - especially as you will also have to replace batteries in them on a regular basis.

Bendo

Like I said earlier in the thread.  I've reduced my own usage by  approx 3000KWh a year from 13000 to 10000. Used rooms heated to about 22 due to wife's Fibro being impacted by cold.

The beauty of logging all temperatures, calls for heat and smart meter data into Home Assistant it makes it pretty clear what works and what doesn't.

Qyburn

BUFF said:

Qyburn said:

One thing I don't think I saw mentioned is that turning down normal TRVs won't switch the boiler and pump off.

that is the role of the room 'stat(s).
having run a system with a programmer+TRVs but no room 'stat I definitely recommend investing in a room 'stat too - it will pay for itself. 

Yes a roo stat will do that, if it's placed appropriately and the room it's in does not have TRVs on the radiators. But what was being suggested is that going round the house adjusting manual TRVs has the same effect as smart TRVs, and its the lack of room by room interlock that means that's not correct.

Let's say in the morning I want to heat kitchen and bathroom, in our case that's the N of the house. And in the evening heat living room and bedrooms at the South instead. If you do that by adjusting manual TRVs morning and evening, how can you have a room stat that works in both scenarios?

Or let's say a spare bedroom, normally unheated but we have guests staying. So whack up the TRV in that room, but that won't help if the room stat "somewhere" decides the house is up to temperature.

Petriix

Qyburn said:

BUFF said:

Qyburn said:

One thing I don't think I saw mentioned is that turning down normal TRVs won't switch the boiler and pump off.

that is the role of the room 'stat(s).
having run a system with a programmer+TRVs but no room 'stat I definitely recommend investing in a room 'stat too - it will pay for itself. 

Yes a roo stat will do that, if it's placed appropriately and the room it's in does not have TRVs on the radiators. But what was being suggested is that going round the house adjusting manual TRVs has the same effect as smart TRVs, and its the lack of room by room interlock that means that's not correct.

Let's say in the morning I want to heat kitchen and bathroom, in our case that's the N of the house. And in the evening heat living room and bedrooms at the South instead. If you do that by adjusting manual TRVs morning and evening, how can you have a room stat that works in both scenarios?

Or let's say a spare bedroom, normally unheated but we have guests staying. So whack up the TRV in that room, but that won't help if the room stat "somewhere" decides the house is up to temperature.

Surely we're talking about an integrated system with a smart room thermostat coupled with smart TRVs? The smart TRVs on their own would be pretty pointless without for the smart thermostat.

With an integrated system, you can set specific temperatures and times for each room. The smart TRVs can call for heat even when the main thermostat is up to temperature. 

Qyburn

Petriix said:.

Surely we're talking about an integrated system with a smart room thermostat coupled with smart TRVs? The smart TRVs on their own would be pretty pointless without for the smart thermostat.

With an integrated system, you can set specific temperatures and times for each room. The smart TRVs can call for heat even when the main thermostat is up to temperature. 

I think there's a bit of misunderstanding. I was responding to the suggestion that a smart TRV system could be fully emulated by changing manual TRV settings at different times of day.

Aside from that the smart TRV systems that I have looked at have boiler interlock integrated, each TRV will call, or not call. The boiler/pump will come on if any valve is calling, and go off when none are. No necessity for a separate "main thermostat". 

BUFF

Qyburn said:

BUFF said:

Qyburn said:

One thing I don't think I saw mentioned is that turning down normal TRVs won't switch the boiler and pump off.

that is the role of the room 'stat(s).
having run a system with a programmer+TRVs but no room 'stat I definitely recommend investing in a room 'stat too - it will pay for itself. 

Yes a roo stat will do that, if it's placed appropriately and the room it's in does not have TRVs on the radiators. But what was being suggested is that going round the house adjusting manual TRVs has the same effect as smart TRVs, and its the lack of room by room interlock that means that's not correct.

Let's say in the morning I want to heat kitchen and bathroom, in our case that's the N of the house. And in the evening heat living room and bedrooms at the South instead. If you do that by adjusting manual TRVs morning and evening, how can you have a room stat that works in both scenarios?

Or let's say a spare bedroom, normally unheated but we have guests staying. So whack up the TRV in that room, but that won't help if the room stat "somewhere" decides the house is up to temperature.

As I said, bedrooms tend to be heated to a lower level than living areas so with a room stat in a living area (or a known temperature offset to give a desired temp in a living area if the room stat is not there) then the bedroom TRVs tend to close before the TRVs in the living areas or the room stat shuts off the boiler. Therefore whilst the boiler may run to heat the living areas the bedrooms are not being heated for all the time that the boiler is running. This is actually pretty close to what I have in my house.
I also said that it's going to vary for every installation/user. Once you really know your system & how the house reacts you can either fine tune or come up with the best system upgrade for your particular house, your typical schedule etc..

Unless you have a massive room to heat & a boiler with a very high modulation ratio/low heating output capability you don't want to be heating a single room only or even 2 as it will cause the boiler to cycle which is inefficient & not good for it's longevity.
The cost of running a heating system in a house is not just the cost of fuel - you can save on fuel but increase costs elsewhere.
Like I also said, it's not simple. Especially as some people respond to efficiency savings by increasing levels (this has been found in studies of both heating & lighting) rather than taking the monetary savings.

Not all "smart"/eTRV* heads have boiler communication/control & some of those that do (e.g. Tado) can still be used/run without that.
You will also find that e.g. Tado & similar offer you the opportunity to use individual room temp sensors in conjunction with their eTRVs because they acknowledge that, by dint of their location right beside the heat emitter, eTRVs may not accurately reflect the temperature elsewhere in the room (I have a classic example of this in my 3rd bedroom, even though Tado allows you to set an offset).

I have a mix of conventional TRVs & "smart" TRVs in my house (more because of geeky interest than I expected them to save money & repay the investment in them). So I do have some actual, practical experience.


* there are different definitions/levels of what constitutes  a "smart"/eTRV

Qyburn

BUFF said:

So I do have some actual, practical experience.

So in your installation, when you want to preferentially heat some rooms at one time of day, and others at a different time, how do you set your room stat? Or do you move the room stat whenever you manually change TRV settings so the room stat is always in an area actually being heated?

BUFF

It's not a situation that comes up with my house, my heating system/the way that is run & my lifestyle.
As I said, my current boiler can only modulate down to 6kW which will heat both of my main rooms, the 3 bedrooms are above those rooms so gain some heat from below even with the radiators in those rooms off or their TRVs set lower. Just heating the bedrooms would have the boiler cycling & as it's a solid-walled house in a Conservation Area (so no EWI allowed) in the west of Scotland with one side directly into the normal direction for prevailing weather could potentially also cause issues with interstitial condensation.

My house is oriented NE>SW so as somebody mentioned is cooler on one side.
Room 'stat is wireless so can be moved but I have 15 years of experience of tweaking this boiler/heating system/house to a point that I just leave the programmer/room 'stat & TRVs to do their things & am comfortable. Only an unusual bout of cold weather would see me interfering with the set schedule/conditions.
Next upgrade expected to be a boiler & controls change when this boiler dies/is an uneconomic repair with one which will allow for higher modulation ratio, load & weather compensation.
That should be something like 5-10% more efficient but again I don't expect the savings from the to upgrade to pay for the capital cost over it's life.

It works for me but I keep coming back to it's not simple, there is no "one fits all" solution so it's going to vary for every building & user according to their heating system, needs, schedule etc.