Is it more cost effective to leave the immersion on all the time?

DarnIt_3

Can someone please clarify whether it is more cost effective to leave the immersion on all the time?

Cardew

It has been asked a hundred times!

No! it's cheaper to have it timed!

Would you leave your kettle simmering all the time - exactly the same principle!

DarnIt_3

Thank you! This is what I said, OH said its cheaper to leave it on! I couldn't see the sense in that belief, so thank you I have just won!

gordon2

Would you leave your kettle simmering all the time

But would the immersion be simmering all the time?

Is it not switched on and off with a thermostat?

Mine is timed but when the water heats up the immersion is switched off by the thermostat, even although the timer says it is switched on.

Pincher

I have just swapped out a dead immersion element thermostat.
The resident had it on permanently for three years since the cylinder was put in, so it was probably clicking on and off every 15 minutes. On the other hand, I have a twenty year old cylinder still on its first thermostat, because it only goes on and off twice a day.

The thermostat is cheap, it's the plumber call out that is the expensive part. So if you are handy, a new thermostat every three years is £5. If you are not, it's £100 every three years.

Cardew

gordon2 wrote: »

But would the immersion be simmering all the time?

Is it not switched on and off with a thermostat?

Mine is timed but when the water heats up the immersion is switched off by the thermostat, even although the timer says it is switched on.

True, but what is your point?

The thermostat will keep the temperature at, say, 65C.

Let us take a extreme example.

You go abroad for 2 years and leave your immersion heater on all the time. Presumably you will concede that it will use more power than if you had switched it off?

So how about 1 Year? - A month? - A week? - A day? A Hour?

Put it this way, at what point do you feel the laws of thermodynamics cease to apply?

gordon2

You go abroad for 2 years and leave your immersion heater on all the time. Presumably you will concede that it will use more power than if you had switched it off?

Is that not a bit silly?

The OP asked about leaving his immersion on all the time when he is occupying his house, not when he is going on holiday.

HappyMJ

gordon2 wrote: »

Is that not a bit silly?

The OP asked about leaving his immersion on all the time when he is occupying his house, not when he is going on holiday.

It's only because this question has been asked one million times (ok that number is a bit silly but it is a lot). Will you save money by turning the immersion off for 17 hours. The answer is yes. You will usually have enough hot water from the E7 heated water from midnight to 7am to last all day. That'll cost 30p a night (6kWh*5p) compared to 72p for all day electricity (6kWh*12p). It will actually use nearer to 7kWh maybe 8kWh as it heating water for immediate use but I won't go into that. The 12p rate I used is not the peak rate on E7 but the normal rate for non E7. My peak rate for E7 is 14p. The £150 annual savings make it worth it to switch to E7 just for hot water.

Cardew

gordon2 wrote: »

Is that not a bit silly?

The OP asked about leaving his immersion on all the time when he is occupying his house, not when he is going on holiday.

No it is not silly.

I was making the point about the law of thermodynamics applying.

If that law applies to 2 years, it applies to 2 hours.

gordon2

Oh I agree, switch it off or have it timed. I just think the comparison that Cardew trots out is a bit missleading.

I have an immersion but it has not been switched on for years, last time was when I wanted to see if it would be cheaper to heat my hot water by gas or electricity, as I have a hot water system that has a pilot light on all the time which uses 4 kWh of gas a day and there is no timer to switch the gas on and off so my hot water is on all the time.

My conclusion was to leave my pilot light on and the hot water on all the time as it was still cheaper than using an immersion.

In the summer with no heating I use about 20 kWh of gas a day for hot water and cooking.

HappyMJ

gordon2 wrote: »

Oh I agree, switch it off or have it timed. I just think the comparison that Cardew trots out is a bit missleading.

I have an immersion but it has not been switched on for years, last time was when I wanted to see if it would be cheaper to heat my hot water by gas or electricity, as I have a hot water system that has a pilot light on all the time which uses 4 kWh of gas a day and there is no timer to switch the gas on and off so my hot water is on all the time.

My conclusion was to leave my pilot light on and the hot water on all the time as it was still cheaper than using an immersion.

In the summer with no heating I use about 20 kWh of gas a day for hot water and cooking.

How much? 20kWh a day is a lot. 7300kWh per year. That's just a bit less than half of the average usage including heating. Are you sure it's 20kWh. I use energy for hot water and cooking and it's nowhere near that. I use about 1kWh for each 6 minute shower and about 1kWh for 30 minutes of cooking maximum per day. My bath water is heated by the immersion which is used on the weekend only when I also wash clothes and dishes as well with the hot water that's 6kWh per week. Are you cooking for a restaurant?