Energy myth-busting: Is it cheaper to have heating on all day?

malc_b

gadgetmind wrote: »

Because even the "cool" return water is hotter than the room, so thermodynamics does its thing. You address the issue of low radiator output by derating them when designing the systems, so effectively fitting "oversized" radiators.

Trust me, my return temperature is around 40C max and we have a lovely warm house. (OK, one room struggles, but that's because I've got some draft issues to address.)

So you are already running in continuously in condensing mode and you have the heating hours as short as possible. That's exactly what I said is the most efficient.

The point is that not everyone has oversized radiators and following the advice of running shorter would mean they would run in non-condensing mode. It's more fuel efficient to heat longer in condensing mode.

Cardew

gadgetmind wrote: »

I'm guessing they use something larger than 22mm!

Whilst I appreciate the benefits of an unvented HW system in domestic applications, along with Smiley Dan I also 'raise my eyebrows' at the thought of this system being used in a multi storey hotel.

Staying in a room on the 53rd floor when the occupants of all 7,000 rooms turn on their 'power showers' would require a pretty large water main!;)

malc_b

victor2 wrote: »

Over-simplified maths?
The above assumes the heat loss is linear, which of course it isn't, just as the leaky bucket doesn't lose water at a steady rate.

Again I point this out on the link and say this, for 8hr night is ~10% error. Simple maths are accurate enough to show the principle. 8% or 7.2% are the same ballpark. There is more inaccuracy on the end temperature which I've taken as 10C (my house I reckon 15C is more like it).

Plus, although it's been claimed I said a leaky bucket leaks at a constant rate I didn't said that. What I was trying to show with the bucket was, if is leaks 10ml per hour then you can either add 10m/hr continuously or 110ml once every 12hrs (assuming a 8% leak saving which would be for a cold house that fell to 10C overnight) . Can the boiler and radiators deliver 110ml worth of energy and remain in condensing mode or will this push them into less efficient non-condensing, in which case the steady 10ml/hr would use less fuel.

Biggles

There are so many contradictory statements on this annual thread (now resurrected for it's fourth successful season!) that I think the only thing I've learned that a fact is only really a fact when it is typed in capital letters. FACT.

Smiley_Dan

There will always be contradictory statements because the word "cheaper" is used in the thread title which refers to financially cheaper. There are many variables here and even the simplest thought experiment exposes them.

If the thread title simply said "use less energy" then there is a clear answer.

wattsupnow

Take a look at my video on YouTube: Home Heating: How the Market is Rigged to Favour Gas.

Ripped out our unreliable and noisy GSH years ago and fitted Dimplex Panel Heaters to every room. Chose their budget panel heaters range (not storage) cheap-and-cheerful and does the job.

We are retired, so leaving the heat on 24/7 suits our lifestyles. Switch them on in October and off about April. Annual costs about £800 for heating and hot water plus about £450 for everything else electric in the house 100% reliable, no maintenance or repair bills. A fit-and-forget solution to heating that keeps the whole house cosy 18-22C all day, every day.

I tried fitting timers to every heater to switch off during the night but honestly made little difference to the bills and not worth the bother.

Richie-from-the-Boro

wattsupnow wrote: »

Take a look at my video on YouTube: Home Heating: How the Market is Rigged to Favour Gas.

Ripped out our unreliable and noisy GSH years ago and fitted Dimplex Panel Heaters to every room. Chose their budget panel heaters range (not storage) cheap-and-cheerful and does the job.

We are retired, so leaving the heat on 24/7 suits our lifestyles. Switch them on in October and off about April. Annual costs about £800 for heating and hot water plus about £450 for everything else electric in the house 100% reliable, no maintenance or repair bills. A fit-and-forget solution to heating that keeps the whole house cosy 18-22C all day, every day.

I tried fitting timers to every heater to switch off during the night but honestly made little difference to the bills and not worth the bother.

Its common knowledge that 'home all day' group can divide annual electric kW and providing the consumption is the ± same kWh twixt any electric heating system @ say 22°C then the £ ÷ period will match up at around £1200pa for space & water heating. You were comparing a knackered old ineffective wet gas system with a low wattage 24/7 panel system my friend.

The heating / comfort profile of a couple such as yourselves with your panel system is totally reliant on the 24/182 running, this way the ∓ never varies by more than a couple of °C and has an added and very welcome comfort element often lacking in on / off stop / start / up / down heating. A reliable electronic thermostat and a timer in a decent standard insulated dwelling is all that's required on a radiant [not convector] panel to achieve good U-value calculations. Congratulations.

schiff

This may have been answered somewhere in this lengthy thread but I have waded through part of it and found nothing. So apologies if it has.

I have a flat in an apartment block from which I am absent for 7 plus days at a time twice every month. Heating is by storage heaters, which I hardly ever use, they are not plugged in (the insulation obviously must be fantastic) and the water is on Economy 7. So, while I am away the water is being heated overnight and never used. I've been told that it's better to leave it on - but I question that, without the necessary knowledge.

I use twice the electricity units on the Economy 7 than I do on everything else and bearing in mind I hardly ever use the storage heaters it seems disproportionate.

Are there any problems with switching the Economy 7 water heating off while I’m away? I’m obviously prepared to wait for hot water on my return.

orrery

schiff wrote: »

... So, while I am away the water is being heated overnight and never used. I've been told that it's better to leave it on - but I question that, without the necessary knowledge.
....
Are there any problems with switching the Economy 7 water heating off while I’m away? I’m obviously prepared to wait for hot water on my return.

It will depend on how good your insulation is on the tank.

Remember that heat leaking from the tank will help heat the building, but that isn't a good way to heat the building.

I'd turn it off, but also consider putting an electric radiator (or 2) with a built in thermostat set very low near to water installations (kitchen/bathroom etc) that may freeze. At least they'll only use power when really needed - probably never, from what you say.

You can answer the question of how much you use leaving it turned on by reading the meter when you leave and then when you arrive back to see what is used in your absence.

Leaving it turned on will reduce the life of the immersion and its thermostat.

schiff

orrery wrote: »

It will depend on how good your insulation is on the tank. (1)

Remember that heat leaking from the tank will help heat the building, but that isn't a good way to heat the building. (2)

I'd turn it off, but also consider putting an electric radiator (or 2) with a built in thermostat set very low near to water installations (kitchen/bathroom etc) that may freeze. At least they'll only use power when really needed - probably never, from what you say. (3)

You can answer the question of how much you use leaving it turned on by reading the meter when you leave and then when you arrive back to see what is used in your absence. (4)

Leaving it turned on will reduce the life of the immersion and its thermostat.

Thank you for that!

(1) I'm not sure there is any, the outside seems to be bare metal.

(2) It is always comfortably warm in the small room/cupboard the tank is in; I put towels etc in there when I leave, to air. The door is usually shut at all times.

(3) I think freezing is a bit unlikely, the flat is in a block and it's on the sea front. The area gets very little snow and frost.

(4) Did that today actually, so we'll see.

One of the reasons for not switching the system off - I've been told - is that the water level in the header tank diminishes. Can be easily checked and topped up though!