Heating on low all day- experiment

[User129867588]

Not sure anyone will find this useful as I know we all have different houses and boilers etc, but I trialled having my heating on all day yesterday, reduced my thermostat to 18 degrees and I spent the same on gas as previous day when the heating was on 18.5 but only on for just over an hour in morning and then for 3 hours in evening! Both days the temp on my thermostat after boiler being off all night was 14.5 degrees 🥶

House is a 2 bed semi, mid 1980’s build. Double glazing that’s over 10 years old and some getting replaced soon. House had insulation added but again that was about 15 years ago.

As seen on pictures the main expense on the gas was when heating first came on and then around tea time. I cooked on my gas hob and then all 3 of us had showers and we use a mixer shower connected to boiler for hot water. I’m with EDF on the variable rate.

I’m doing it again today and if it stays around the same I don’t see any reason for me to work in a cold house in the daytime when it costs the same (or just a tiny bit more) to heat most of the day! I can manage with 18 degrees too and still wear a jumper and extra thermals. Last years 20 degree heat is but a distant memory…….

Just leaving this here in case it's informative to someone .It wasn't especially to me -seems so much depends ..
www.theguardian.com/money/2022/dec/05/a-hot-topic-in-an-energy-crisis-how-efficiently-are-you-using-your-boiler

Flow temperature dictates how hot the boiler heats water, and is usually set at between 70C and 80C when the combi boiler is installed. But this is too high for many boilers to operate efficiently, according to energy company EDF.

At lower temperatures, they go into condensing mode more frequently, so more heat can be captured and recycled into the system.

Combi boilers often work best when they heat radiators to 60°C or below, according to Nesta, the agency that promotes innovation. This does not mean the temperature of your home will be lower, but radiators will take slightly longer to heat up.

Some households leave their boiler on “long and low”, or permanently at a lower temperature for the whole day, so the machine has less work to do and spends less time in an inefficient mode trying to get up to a certain temperature.

However, Alsop says this has been shown to use more gas, and that a timed regime – where the boiler is switched on for set periods, such as two hours – is more efficient and can save £130 a year.

Has anyone else done the experiment? This is an interesting thread as we’re already seeing quite a big variation in results.

However, Alsop says this has been shown to use more gas, and that a timed regime – where the boiler is switched on for set periods, such as two hours – is more efficient and can save £130 a year

But who only has it on for two hours in winter? Either people who are up against it financially or people who don't spend much time at home. For people who have an additional £130 per year and spend a long time at home, then they could be in a comfortable temperature throughout the day for far less than they have been led to believe.

And it's not clear from the article if they are comparing the two situations, on for the day or in bursts, with the flow temperature running high or with the flow temperature down.

In 4 bed old house. Tried this and alot more to heat all day than for a few hours. It is true first hour most expensive so definitely better to do 2 hours in the evening than 1 in morning and 1 in evening.

We tried having it on all day at a low temperature when we first moved to this house. It’s an old house with poor insulation. The gas bill was eye-wateringly expensive after one month so we’ve reverted to a couple of hours in the evening ever since.

Fourtea - I don't pretend to grasp the intricacies of articles like Alsop's ,but I thought the reference was to 2 hour periods of time rather than only 2 hours a day .

But is she referring to a combi or not in that para?

I’ve been doing this since buying my house 10 years ago. Thermostat has always been set at 21 degrees at key times and 19 degrees at all other times, all year round.

Average consumption over the years has been about 13000 kWh per year, so not much above the average of the price cap for typical users. Two bed Victorian semi with a combi boiler.

It's less work on the boiler to fire up at full speed every day, just gently ticking over.

Boilers are on or off. What varies is the amount of time they are on. Gently ticking over surely means off.

At the moment it costs me £1 per day more on gas to have the heating on all day than just to have it on for two short periods. However I am still on a low cost fix. It will cost me more in January I expect.

What also comes on is the electric pump whcih pumps the water round.
So running a pump on and off all day is using electricity.
Seems a fan comes on too which comes on first and blows away any residual fuel from the burner. Then theres a woosh as the fuel ignites, the fan also runs as providing air for the burning.

I would be interested to know if you can run heating all day but turn off eg the upstairs radiators as not in use. Then maybe before bed time open the doors to the bedrooms to let the warm air in. So heating a few rooms all day not all rooms.

We have a separate thermostat upstairs which is very handy.

I had the heating flow rate turned down but found it took so long to reach the thermostat tempertature that I ended up having the heating on for longer to compensate. So I turned it back up. (I turned the hot water flow rate down a whileback and that's been fine).

I'm going to try to turning it down again, but having the radiators on for MUCH longer so that it can reach a steady state.

1920s semi, windy spot oop north. New combi boiler. Double glazing a bit old. Loft v well insulated but cavity walls not (I was accepted for a grant to get them insulated then was told that I shouldn't have it done as they're stone, and stone is less porous than brick so CWI in a stone house can give you massive condensation problems. Is this true?)

I was inspired by this thread to do a comparison. 3 bed house, detached (but very close to another house on one side). Cavity wall insulation, double glazing, curtains have thermal linings. Boiler is about 9 years old.

For Saturday - heating on for 4 hrs a.m. and 3 hrs evening only, not during day - used 52.7 kwh

For Sunday - heating set to be on throughout the whole day (thermostat set to 17) - used 62.6 kwh

So we did definitely use more with having it on through the whole day, however the price difference is quite low (on our current tariff).

Victorian uninsulated brick house. High ceilings. No heating at all in the kitchen.
It's 12/13 degrees in the house. We have tried heating 1 hour morning & evening. But it's so cold today. Might try putting it at 15 all day. (18 would bankrupt us.) We work from home, and there are no more layers we can put on 😩

There are insulants you can use...but there's nothing to stop the moisture passing thru the stone and crossing the "gap" (tech term "Cold Bridging) iyswim (DH is a surveyor).
The only alternative, really, would be some kind of thermal backed plasterboard on the inside of each external wall - which would make your house smaller.
Sorry.

Does anyone know if this works with oil heating? I always want to try leaving it on with thermostat turned down lower, but there’s not really any way of knowing how much you’ve used and this year it feels to risky to experiment with.

The whole thing is so poorly phrased that you can't tell.

I've been trying this too! I have fellow experimenters! Is that a word? 🤣

That's true of electric heating and old non-condensing boilers, but modern boilers have varying levels of efficiency and can also modulate themselves so that they put in a smaller amount of energy if required. I guess the key is whether the increased efficiency by running low and slow is outweighed by the increased energy loss by having a warmer house. Seems like there is no absolute yes or no and depends on the house, boiler, thermostat temperature (and probably outside temperature too).

I've turned it into a "keeping my heating on alllll the time" experiment.

My heating yesterday was at a min of 19 all morning from midnight/the day before, cranked up to 20 from half five and then down to 18 from ten pm.
It used 61kwh and cost me £6.24 up to midnight.

It's been left at 18° since then, and used 18kwh up to half twelve this afternoon, so £1.84.

I've just been speaking to Asthma & Lung UK, and I'd got my minimum recommended temps wrong for COPD. I thought it was 18 living room/ 15 bedroom - it's actually 21 living room/18 bedroom. Hells bells.

So experiment complete:
Large 3 bed semi built 1950's. Double glazing but this is 20yrs old. Deliberately did this over a weekend when 5 people are in the house both times (not at school/work which would be cheaper for electric). Gas central heating and water tank heated by gas. We have a multi stove in the lounge. No smart meter.
First 24hrs - 3x hour boosts of heating (to what ever temp it got to in that hour). Not on at all after 8pm. 2x water heating. Stove lit at 1pm. = £4.60 gas.
Second 24hrs - thermostat set to stay at 18' between 8am and 6pm then 19' 6pm - 8pm. Set for 16' 8pm - 6am then up to 18' again. 2x water heating. Stove lit at 1pm. = £4.60 gas.
Honestly the same price.
And this is direct meter readings at the same time then doing the sums.
I realised that the house actually holds the heat well and that the first boost in the morning was only getting the temp up to 16.5'. It took another hour to get up to 18'. But the house felt warmer and less condensation on the windows and was just more pleasant to be in. Obviously we are lucky to have the stove and by the evening, the heat is spreading around the house.

I also measured the electric and found that with everyone in the house all day, a teenager gaming, TV on all day, washing machine, tumble dryer and dishwasher all been on once it was £2.80..... both days, the same.
I measured the tumble dryer and it was 60p to dry the load. I'll take that rather than my house being a laundrette and additional damp issues that would cause!

Obviously if your house isn't well insualted it will lose heat faster and therefore your boiler will be on more to compensate, and also we aren't quite in baltic temps when the house temp will drop more, but 18' is the minimum temp to prevent damp and mould and just for better health.
So it's staying on.

Definitely worth people testing this theory rather than being miserably cold and risking health and property.

Are you sure they aren’t averages though. The chances of your gas use being identical both days are slim. The chances of both your gas and your electricity being identical both days are close to zero.

Interesting point....I will take the readings again tomorrow and report back.
To be honest, electric was actually 1 unit higher so and additional 34p, but gas was genuinely the same.
But how would an average work out when your meter is meant to go up as usage goes up? And at what point does it calculate the average if this is the case?
But it surely stands to reason that if both days were essentially the same, same things happening, that it would be almost the same both days?
If not, then there are bigger issues as to how people are being charged and how are they meant to budget and keep an eye on things?

My smart meter shows averages for periods where the communication has been interrupted. So I’ll suddenly get whole blocks where my electricity will show as £7.62 for example.