/ Home & Energy

Tricky thermostats – is your central heating out of control?

Some tiny plumbers fixing a radiator thermostat

Keeping our homes warm during those chilly winter months is essential to most of us, but are you spending more money on heating than you need to? Are you in control of your thermostat?

In our recent heating survey we found that around two thirds of people with central heating have a timer to turn the heating on or off. But only half have thermostatic valves on at least some of their radiators. And less than half have individual room thermostats.

To get the best out of your heating system and save money, each house should ideally have a full set of controls:

  • A timer or programmer to set when your boiler should turn on and off.
  • A room thermostat to set the temperature you want your heating to achieve.
  • And thermostatic radiator valves to control radiators in each rooms.

The Energy Saving Trust estimates that you could save £70 per year on average if you were to install a room thermostat (in a typical three-bedroom semi-detached home heated by gas).

A flexible approach to heating

As David W put it in a previous Conversation about heating:

‘What one really needs is a device that compares the ambient temperature with a pre-set ideal and switches on the heating if (and only if) it’s needed, summer or winter. Because if it’s cold, it’s cold, whether it’s August or December.’

A letter we received from Mike Astill suggested the use of portable wireless thermostats. He moves the thermostat from living room to bedroom etc as he moves around the house. He also turns down the radiator valves in the rooms he’s not occupying.

Confusion over complex controls

But even if you have a heating timer, do you know how to use it? Some are quite complex and not at all intuitive. One in five people who have a timer and don’t use it, say it’s because the timer is too complex to use or they don’t know how to use it.

When first installed, your heating engineer should explain how to use the timer and the thermostat, but do they? In detail? And what about if you move into a house that already has a timer, but the previous owner has not left any instructions for the boiler or controls? How do you find out how to use them?

Our research also found that almost one in 10 people who don’t use a timer for their heating say it’s because they believe it’s more efficient to leave the central heating on all the time.

Do you have a full set of heating controls in your home? And do you know how to use the timer? Do you have any tips on how to make the best use of heating controls to save money while still being comfortable in your home?

richard says:
6 February 2013

When I installed central heating in my six bedroom house in 1980 – I installed thermostats on all radiators and a central thermostat – May explain why my winter heating bill is under £25 a month. It is easy enough to work out how to use the controls – a day trying various settings will give you the idea – I’ve done it for a couple of friends. The trouble is too many people won’t be bothered.

The concept that a central thermostat can decide when the boiler needs turning on to provide heat to any room seems absurd especially in older houses and where all the rooms are not used all the time.
Although I have one fitted I only use it turn the system on and off at night and when we are out during the day, the room where it is fitted is now controlled by radiator thermostats. The boiler itself has enough logic to stop “short-cycling” operation.

What is really needed is thermostatic radiator valves which can individually call for heat ( switch the boiler on) as required. Although they are now available the cost is prohibitive.

My biggest cost saving is to make sure the house isnt heated when we are out and to spend more time out of the house !!

It used to be common to put a room thermostat in the hall. I assume that current practice is to put thermostats in room(s) where people spend most of their time, but there are still plenty of houses with a thermostat in the hall.

Unfortunately, thermostatic radiator valves are still with us. When I was a schoolchild I knew that it was not a good idea to put a thermostat next to a source of heat. A TRV will increase and decrease the heat output from a radiator but to achieve proper temperature control it is necessary to have the temperature sensor distant from the heat source.

You are correct about room stats, they always were put in the hallway and that is not the best place for them. Remember the room stat is the overriding control which when the set temperature is reached switches the boiler off. When this happens it makes no difference at all what you’ve set your rad thermostats to, the system is off.

My approach is to put the room stat in the room you use the most or want the warmest. Use a wireless room stat and you can if you wish vary the warmest room. Also it you have rad stats on all rads make the one set wide open (there has to be one or you need a bypass valve) the one in the room you put your room stat.
Rad stats on all other rads in other rooms control the temperature in those rooms (or actually flow of hot water through that rad) but that temp will always be no more than your warmest room.

As for rad stats not being any good because they are so near the rad, well yes and no. A remote room stat would work better but would not be economically viable.
Simple rad stats work because they are not calibrated in temperature, rather they are scaled in simple numbers usually 1 to 5. In this way through a bit of trial and error it’s possible to set a maximum room temperature using a simple cheap temperature sensitive flow control valve.

So in summary my tip for most economical heating is.

Room stat in warmest part of the house and set it a couple of degrees lower than you want the room to be. Warm rads still give out heat for a while after the boiler stops boiling.

Radiator stats set to give the same or slightly lower temperature you want in all other rooms.

And leaving the boiler on 24 hours is not the most economical approach. Your house has a heat loss factor all the time heating on or not. Why feed that heat loss when you’re not there or are curled up in your warm bed?
Perhaps a compromise is to turn the room stat right down (15 degrees or even less) when you are out or overnight to prevent the house becoming too cold and taking a long time to warm up again. But trying to maintain your normal temperature 24 hours is a waste of money.

This is more or less what I do, Chris, though I updated my controls before wireless thermostats became available at a sensible price. My thermostat will turn on the heating if the temperature falls below a certain temperature when the system is ‘off’ overnight, though that does not happen very often.

Having a zoned system with two or more room thermostats is probably economical if you can do the job yourself rather than pay to have it done.

I’m afraid I’m one of those people who currently has a thermostat in their hall and, unsurprisingly, my hall is one of the coldest places in my house. We have the thermostat set to around 16 degrees and the hall never reaches that temperature.

so why not turn it up slightly?

David Knowles says:
19 March 2013

I see this as the correct place for it. All you need now is radiator stats and you then have control of the temperature throughout your house.

My controller programmes daily times for hot water and heating separately, with setting buttons, overrides and sliders, to give very flexible control. It does need a bit of effort to set it, but the cover tells you step by step exactly how to do it. As they say, if all else fails read the instructions.

I have a single thermostat in the living room – where of course we spend most time. The setting has been adjusted with a simple thermometer placed in different parts of the room initially so we have a comfortable temperature. Other rooms have thermostatic radiator valves that are, I believe, necessary to meet building regs on new or replacement installations? Better than nothing – again, by adjusting them and checking the room temperatures I’ve had acceptable results.

I confess, though, that my heating does not go off at night, partly because we are late to bed. Although the house is well-insulated, to get back to temperature in the morning takes a little time – and it is nice to have a warm house if you need to get up in the early hours. Clearly it would be cheaper to turn it off for 4 or 5 hours, but I have not worked out just how much we would save – reheating will eat up part of that saving. Afraid comfort wins over the pennies (soon to be tuppences).

My room thermostat incorporates a timer and I find it very easy to make changes to the operating times and room temperature when needed. When the heating is off overnight it will come on if the temperature falls below a certain temperature, but that rarely happens. If I am ill and might have to get up in the night, I increase the temperature. If I am going away it just takes seconds to lower the temperature to ensure that there is no frost damage, for example over Christmas when I am away. I use the programmer to provide more hot water at the weekend, when I run the washing machine and generally use more hot water. My favourite aid to comfort is a fan heater in the bathroom.

Not everyone gets on well with complicated times. At Christmas I swapped a sophisticated controller for a simple one, for a friend’s elderly parents.

I live in a Edwardian terrace, solid walls, single glazed windows (don’t get me started on the con that is double glazing). When we bought the house it came with ’80’s era central heating including TRV’s on nearly all radiators. Problem is most of those TRV’s don’t work properly and need replacing.

Cheap TRV’s have a habit of getting stuck or not working properly over time anyway so there must me thousands of homes in such a situation.

We have a new boiler and supposedly clever programmable Thermostat, but my partner often is at home during the day and as such has the heating on. Even though she’s only using the living room and kitchen, the whole house is being heated (not cheap in said house).

We do need to move to programmable TRV’s, but as has been said above these are expensive, up to 3x the cost of a good TRV. They are also not very well designed both in function and looks. What’s needed is a Programmable Thermostat that links to (affordable) programmable TRV’s with a simple room by room control system that average Joe and his grandmother can figure out.

Malcolm Duke says:
8 February 2013

TRVs do sometimes get stuck and not work properly. A few smart taps with a hammer will often get them working again.
Unscrew the plastic control unit, and tap or press down on the pin underneath. This should move freely. Sometimes a tap on the side of the valve will get the same result. I got this tip from my heating engineer, and it’s much easier and cheaper than getting a replacement fitted.

I rent a new build flat with underfloor heating. Each room has its own thermostat and timer, helping me to only use as much heating as I really need.

The only problem is that there’s no heating in the bathroom. It’s a tiny room, but it can still get pretty chilly!

Richard, can you give a fuller description of your property? £25 per month to heat a 6 bedroomed house in the winter is very economical. I guess you live somewhere in the South. of England, the house is a modern terrace and only a part of it is actually heated to 18-21 degrees C probably only in the evenings and weekends.
We have a 4 bedroomed detached 1980’s house with full double glazing, cavity wall insulation, 30cm loft insulation, condensing gas boiler with programmer, lounge thermostat and TRV’s on all radiators.About one third of the house is heated to 18-21 degrees C during the whole week excrept at night. Our December 2012 gas bill was £88.

David Knowles says:
19 March 2013

I don’t know about the south of England, more like the south of France

Scott says:
9 February 2013

I have recently replaced a 1980s boiler with a new condensing Worcester Bosch boiler and got an external temperature sensor fitted with the boiler. Instead of the thermostat inside the house you fit a weather compensation controller/timer in its place. The savings are massive!
The boiler reacts automatically to temperature inside and out, keeping the boiler in condensing mode(the most efficient mode) for as long as possible.
The heating also won’t come on when it’s hot outside.
You can also set the heating to holiday mode. This means instead of programming the heating to come on for a couple of hours a day when you are away (whether it is required or not) the boiler simply keeps an eye on the house and outside temperature and brings it above freezing if required. So no more wasting energy when you are away from home.
The only slight difference to a normal thermostat is the fact that the radiators run at a slightly lower temperature. Still keeps our big old house warm.
So if you want to take your efficiency to the next level you should look into getting weather compensation fitted to your boiler (if possible. Most of the high quality boiler manufacturers offer this)

Why doesn’t Which look into weather compensation systems on boilers?The price difference was minimal when we installed it as part of the boiler replacement instead of a thermostat and we have noticed huge savings.

I have thermostatic valves on the rads (except hall), but the best contribution is a programmable thermostat where the temperatures can be set to be different at different times on each day of the week. Cost about £20, took an hour or two to set up (probably 8 or 9 years ago now). I means we can reduce temperature at nights , but not turn off completely so on really cold nights it keeps a minimum temperature, Also different temperatures during the day if we are out working, but higher in the evenings and at weekends.

Also has a holiday button where you tell it how many days you are away and just keeps the minimum temperature in the house (I have set for 10 C) without full heating.

Mine is similar except that I cannot have different settings on each day and there is no holiday button. It’s older than yours and cost a lot more.

I have thermostat envy, Phil. 🙂

We, like Phil, have a programmable room thermostat, and can definitely recommend them. It was easy to install (straight replacement for previous rotary thermostat) and means we can set different temperatures for morning, daytime and evening as well as weekdays/weekends – and it has overrides for holiday, staying up late, and day off (the latter temporarily applies weekend settings to a weekday).

The really clever bit though is ‘Optimum Start’ which adjusts the time the heating comes on in order to reach the chosen temperature at the chosen time, depending on how cold it is. Clever stuff.

KJR Johnston says:
22 February 2013

My wife and I are retired so the house is usually occupied during the day. We live in a recently converted, open-plan cowshed with water underfloor heating. The original control was a complex unit with zones, multiple timing and temperature selection and numerous other options. We never got it working satisfactorily or really understood it. We replaced it with a simple thermostat and no timer. It works perfectly. During the night, when the temperature drops, the heating comes on and switches off at 18 (the thermostat setting). Heat continues to come out of the floor so that, when we get up, the temperature is around 20. It stays like this all day. The heating rarely comes on during the day unless a window or door has been left open. The only loser is our collie who dislikes lying on a warm floor and spends most of her time outside regardless of the temperature.

With a well insulated house there is much to be said for keeping the heating on 24/24.

fred morrad says:
22 February 2013

We have a zoned system gas fired central heating. The zones are pumped . The zones have individual thermostats and timers. We have a remote radio thermostat in the lounge. It has proved extremely effective and has the advantage of being programmable on a weekly and and a daily basis. The daily basis can be instantly altered if need arises, but is routinely set lower in the morning and higher at night. We are gradually installing TRV’s as we decorate, but have several installed already. As has been said, the combination of timers and (programmable) thermostats gives a flexible and effective system.

It sounds as if you have a very versatile system, Fred. I’m surprised that you are installing the TRVs progressively because this involves draining the system several times. It’s normally much easier to drain once and swap all the valves.

Mike Cowlishaw says:
22 February 2013

When replacing a failed boiler last autumn I also replaced the ‘dial’ thermostat with one that has timer capability. What a difference! We have ended up with boosting the temperature by just one degree in the early mornings and around mealtimes, and allowing it to drop by 8 degrees overnight. Net result: no longer shivering on getting out of the shower or while cooking/eating .. yet this January used 40% less gas even though the degree days up 30+% on last year. New boiler probably explains a third of that difference — but the key issue is significantly improved environment at less cost.

I’d love to have a heat pump and exchanger in the loft, but that is prohibitively expensive and almost impossible to duct and install. I know it’s anecdotal and can’t be proved, but I find that by keeping the house at a constant pair of temperatures – 20 degrees day and ten at night (ten pm -6-o-clock) the plasterwork doesn’t crack and the house is always warm and welcoming. I have a wireless control in the hall and rad valves on everything and a combi boiler. The heating comes on when it wants to all year round. The hotter it is outside the less often this happens. Occasionally it gets caught out by a cold summer start, but not often. If sendentary, (typing on Which Convo sites), I can boost the room with a fan heater, also thermostatically controlled. I’m afraid I’m too lazy to tweek controls and probably pay the price for this, but no-where in the house seems to be above the thermostat setting so there doesn’t seem to be a need to do so. My caring duties mean absences, and I like to think that the house remains stable and constant whether I’m there or not.

Michael Wild says:
23 February 2013

I have a multi-fuel stove in the living room that provides hot water and runs enough radiators to keep my old house warm. If it’s cold I put on another log or a shovelful of smokeless fuel. As far as the control system is concerned I take King Louis XIV as my inspiration i.e. ‘Le thermostat, c’est moi’.

AlanW says:
23 February 2013

I am confused as to why I have a Honeywell remote thermostat and fitted radiator thermostats in the same room.
The Honeywell remote controls the temperature very well with the added advantage of being able to allow for holidays and extending the ‘On’ time for social occasions. So why do I need individual radiator controls on radiators in the same room? Also what setting should I have them set to so as not to conflict with the remote control? I guess the radiator controls should be set to fully open but no-one gave any advice when they installed my new boiler and remote thermostatic control.

If your thermostat is a wireless unit that can be moved between rooms then that might be the reason why there is a TRV in the room that currently has the thermostat. If not then it suggests that the heating engineer was not very clever.

Colin says:
23 February 2013

To save hugely on energy and feel comfortable wherever YOU are, wear thermal underwear. A little Merino wool in your long sleeved vest and long johns will enable a 5 degree reduction on the ‘stat and a fresher environment. The lower temperature ‘head’ – (the difference between the temperature inside and outside) – will also greatly reduce heat loss to the atmosphere. Keep room doors closed. ‘Open-plan’ is a redundant legacy from the days of cheap energy. A door on the stairs, once standard practice, is a major contributor to comfortable conditions and efficient fuel utilization.

I live in a 3-floor 4-bed Victorian semi-detached house. We had TRVs and a single wall thermostat – very difficult to get good temperature control. I have now fitted HouseHeat wireless controllers. They replace the TRV head and each room has its own wall thermostat (apart from toilets, bathroom, shower room which still have TRV or conventional valves). Each room ‘stat is programmed separately with two temperature settings and time blocks for switching between the temperatures. The old wall thermostat has been replaced by a control unit which receives call-for-heat signals from the room ‘stats and then switches the conventional CH controller. The room ‘stats have also got manual override and holiday mode – they can be switched to stay at the low setting until the day we get back. We have not saved a great deal of money, but the temperature control is much better than previously.

It is interesting to read about the technology that is now available to control the temperature of our homes, but it does not solve the problem that many couples seem to suffer from – one is forever turning up the thermostat and the other turns it down.


The marriage guidance councillor may advise a cooling off period before taking action. 🙂

Malcolm Duke says:
24 February 2013

I’ve got a solution to the problem of one person turning the thermostat up while the other turns it down.
I heard of somebody who disconnected the thermostat in the hall (this is what his wife turned up) while he wired in another ‘hidden’ thermostat to control the boiler (which he operated). Everybody happy!

We have a Klimat K2007 it is so intelligent as it constantly takes four temperature readings outside, inside, the boiler the hot water tank(if you have one).
What temperature! you don’t notice the temperature change, even when it is minus 12 degrees outside, in fact you feel as though it is warmer. If you feel really cold then you can override the set temperature for 20 minutes, that only happens if we feel unwell, or stay up late.

Its brilliant and we are using only metered 165 units a year for central heating in the winter its on all day long. Having just checked the figures it looks like we are saving 30% we are amazed.
At the press of a button you can go on holiday , but has the bonus that the heating will kick in if it falls below a set chosen temperature. Who wants to feel cold.