Which is best, hot water boiler on all day or once/twice per day? (merged threads)

toshkininny

Just out of interest has anyone worked out whether it is cheaper to leave the water boiler on all day, or turn it on and off as and when you need it?

wallbash

Will be killed by those that are green :rolleyes:
But ours are on 24/7 , tank is extremely well lagged.
Could never see the point of heating a tank..... allowing it to go cold only to then fire up the boiler again.
Suppose it depends on your life style. If you are out all day

Some bright spark will telll us about a combi boiler
But my house has warm air central heating. AND a power shower.:D

Barneysmom

We've got a combi boiler but even if we had a different sort, I'm too scared to put it on the way the gas rises are coming soon.
The shower's fab though.

toshkininny

I was always one to turn it on and off as and when required, but then my dad said he left theirs on and I started to wonder what's the cheapest way!

WestonDave

In simple common sense terms - if its going to go completely cold and stay cold for a time before being heated again its cheaper to turn it off because the time it is fully cold it is saving money. If its going to stay warmer than the room the cylinder is in, and then you heat it back up again before it gets cold then its probably borderline.

There is an argument that the hotter the water is the more heat it loses to the outside and therefore you are wasting energy keeping it that hot but that gets into complicated maths!

Barneysmom

I wonder if another layer, bubble wrap, would keep even more heat in?

toshkininny

you could try it and let us know?!!!

wallbash

If you are that way inclined, forget bubble wrap , just get another tank jacket. Well wrapped tank beats ANY other isulation cost wise. Quick pay back.

TimBuckTeeth

As mentioned above the hotter the tank (above room temperature) the faster the heat loss (wasted energy). Letting the water tank cool reduces the rate of loss of energy.
Also turning the water thermostat down to 65C (but no lower to prevent bacterial growth in the system) will save energy by reducing heat loss and water that hot needs to be mixed with cold anyway.

If the water in the tank goes cold during the night then better insulation is needed. The only time a tank full needs to be heated from cold is when it has all been used or the water heating left off for a couple of days.

It might seem to need a lot of energy to heat a tank from cold, but this is needed anyway if a tank full is used (baths etc.), keeping the water heating on uses the same amount of energy plus extra compensating for the heat loss.

For example, if the tank cools from 60C to 40C during the night then the amount of energy used to heat it up to 60C again in the morning is less (due to the lower rate of heat loss) than the amount of energy needed to keep it at 60C all night. If the hot water is all used up (cold tank) when the timer switches off then no energy is lost during the night.

It is impossible to use less energy keeping a water tank hot all the time, that is why timer switches are used for water heating. It is convenient to have hot water always available but it is more expensive, how much depends on the boiler efficiency and system insulation (tank and pipework). Combi boilers are popular because they are more efficient as they only heat water as it is needed.

totalsolutions

Electric hot water tank?? Use a dual element immersion heater 27" and 11". The short one can be controlled (on/off) by built in thermostat and the long half can be switched (timer) on over night (cheap rate electricity) for a full tank in the morning.

amcluesent

CH/HW controllers are getting more sophist acted, now you can get a weekday/weekend/3-event job you can pretty much define exactly when to ignite the boiler to give just the HW needed each day.

Plus lag the tank well of course!