Wireless / smart TRV's.....Are they worth it?

Will_I_Am

Hi
I'm trying to decide if it's worth the cost of installing wireless or smart TRV's on some of our Rads.

We have a conventional boiler (I don't think it's opentherm compatable) controlled by a Nest thermostat.  We have 4 bedrooms upstairs which are empty all day but either my wife or I are generally working from home downstairs so will want some heating on.  My thought is that installing wireless TRV's or the rads upstairs would mean I can effectively create a zone upstairs which I can turn off during the day, then back on again in the evening to warm the bedrooms a bit before the kids go to bed, but allow us to be downstairs in some degree of comfort.

However, I've heard suggestions that wireless TRV's are not really a money saving tool, and really just stop you being lazy....but as it stands I'm not going to go round the house every day turning each rad down whilst the kids are at school.  If I invest in 5 wireless TRV's at around £200 - £250, am I likely to see much impact on my gas bill?

Thanks for you suggestions

macman

Yes, it will reduce your consumption, but whether you'd ever get back the capital cost is impossible to say.

Astria

Considering the cost of them, I wouldn't suggest they are a cost saving currently.

Personally I prefer to turn down all the radiators in rooms not used much and simply leave the doors open, the heat from the rest of the house will bring the rooms upto temperature and then just close the doors when you are done with that room.

For example, a dining room which you might use for an hour, does it really matter if it's a few degrees cooler than the rest of the house?

mysteryUser

I've been using smart TRVs for many years. The first ones I got weren't hugely smart, standalone devices which you can set schedules on. I'm sure the marketing on those back then were that they could save 'up to 30%' off your bill. 

I now use Drayton Wiser stuff which I really like. Controls the boiler directly too, so if I want a boost of heat just in the bathroom to dry the towels or something I can just twist the TRV in there and it'll heat just that for an hour. 

I guess these things are a bit tricky to calculate savings.... let me do some educated guesswork....

If you've got 4 radiators with them and each radiator is 0.5kW output, then if they were all on max they'd be using around 2kW of gas I'd think. As an example, if they saved 4 hours of output each day at 2kW then you'd be saving 8kW per day. Over 90 days that's 720kW, or £108 at 15p per kWh. 

BUFF

There was a thread on this not long ago. Recent research suggests that, on average, it is only a few % saving over already having conventional mechanical TRVs. Of course, it all depends what you are coming from in terms of already fitted equipment,  your lifestyle & what changes you make to your behaviour  - some will save more, some will save less & according to the research some saved nothing at all as they chose to use the control/saving to increase their comfort level..

doodling

Hi,

A lot depends on how you use your house.

If you are out all day, come home and spend a few hours downstairs before going to bed then you probably won't save very much compared to normal TRVs and a thermostat in the most used room.

If you are working from home and just want to heat one room, or different members of the household using different rooms are on different schedules ,or you have a large house with infrequently used rooms then the savings can be greater.

I fall into the latter camp and went with Honeywell EVOhome.  The system cost around £1600 (excluding installation which I did) but it is a big heating system (28 radiators, (grossly oversized!) 60kW boiler) and the system appears to give me a 20% saving which on what was a £2k gas bill (now rather more!) giving a reasonable payback period.

Will_I_Am

Thanks all for your advice. We’re currently paying about 8p/kwh, and have the rads on about 2 or 3 normally so it sounds like it might not be worth it right now. That said, with energy prices going up, it may be worth it going forward.

ManMadeWays

Across 15 radiators I fitted 13 Drayton Wiser TRVs (Bathrooms were excluded) , Vaillant Ecotec 937 Combi.

I also tweaked the DHW temp down a bit and CH temp down a bit at the same time, 5 adults here with different patterns of use across bedrooms and living rooms etc.

And 3 WFH in seperate rooms.

Our gas was approaching 28,000 Kw/h, for a full year of use I am expecting to drop to 18,000 Kw/h, also Electric Kw/h savings as the boiler not on so long.

Savings Gas 10,000 Kw/h @24p K/w/h (my expected weighted average in 2023) is £2,400 (plus some leccy) , at a cost of about £600 that is some payback.

At only 6p a unit the payback is a year !

Your mileage may vary of course !

BUFF

Did you have existing TRVs where you have fitted the eTRVs? Did you already have a programmer/ room 'stat too? Was the Vaillant boiler existing or a new installation?
You have adjusted your  DHW & CH flow temps - how much of your hoped for 10,000 kWh annual saving do you expect that to account for?

It will be interesting to see if you get your hoped for saving (~35%). Please post your results achieved after a full year of use (when did you fit them?).

Petriix

If used properly and you isolate the rooms effectively then they will certainly save you money over just leaving the radiators on. Given that typical gas bills will be around £1500, a 20% saving will pay for the TRVs in the first year. 

BUFF

the recent research suggested that it was ,iirc, more likely to be on average ~3% over mechanical TRVs (again, some saved more, some saved less & some saved nothing at all because they used the increased control to make decisions favouring comfort ) .

But it is going to vary according to how people live in their houses & how their houses are built (probably more useful for more modern highly insulated buildings rather than older "traditional" buildings).