Immersion Heater ... on 24/7 or only when required ?

zappster1966

Dunno what to do.

Use the electric immersion heater only for washing the dishes & shaving, washing hands etc. We have a bath once or twice each week, rest of the time rely on the electric shower.

The "older folks" in the family say it's cheaper leaving the immersion heater on 24/7, rather than continually switching it on & off ("you're always having to heat a whole tank of cold water every time you switch it on ... wasting electricity").

Thoughts ?

aamuk

I would go with the only switching it on when required option. You will have to learn how long before you want to use it you have to switch it on to give enough hot water for the particular use, say 30 minutes or an hour before.

To prove the point, try it both ways on different days that have similar useage and look at the meter readings (take into account other electricity use when the average use would be similar for a day).

Cardew

This has been covered dozens of times on this forum, and the answer is that timed is cheaper. No question - not even worth debating!

The analogy normally used is that if it is cheaper to leave something on 24/7, rather than heat up from cold, then why not keep your kettle simmering 24/7? It really is exactly the same principle.

That said, the difference betwen timed and 24/7 is not as large as many people think. A well lagged tank will lose between 2kWh to 3kWh in 24 hours, and even a timed tank will still lose heat. So probably 1 to 2kWh a day loss for most people. That lost heat is also not wasted for much of the year as it warms the fabric of the house.

skelly01

I have just done this exercise and switched off from always on to timed only. I am saving 6 units (Kwh) over a 24hr period.
I have a new (18 months old) tank, which is manufactured by saniflo.
All adds up to quite a saving!

Magentasue

skelly01 wrote: »

I have just done this exercise and switched off from always on to timed only. I am saving 6 units (Kwh) over a 24hr period.
I have a new (18 months old) tank, which is manufactured by saniflo.
All adds up to quite a saving!

Thank you for this. Last time we had an immersion heater, we found similar, yet most people on here think the difference is insignificant. I'm sure it varies according to when and how much hot water is used, but for a large family like us, it was much more expensive to leave the immersion on, even though the tank was well insulated.

Cardew

skelly01 wrote: »

I have just done this exercise and switched off from always on to timed only. I am saving 6 units (Kwh) over a 24hr period.
I have a new (18 months old) tank, which is manufactured by saniflo.
All adds up to quite a saving!

Whilst, as I posted above, there will clearly be a saving, I really have to question those savings - at least for the majority of people.

All HW tanks are tested to a British Standard and the losses should be available - you should have a sticker on your tank.

I have not seen a modern tank(with the foam type insulation) that will lose more than 3kWh in 24 hours. This is with a full tank at 60C.

Given, that even when timed heating is used, there will still be hot/warm water in the tank for some periods - and consequent losses - it is difficult to envisage losses of more than 2kWh a day.

May I asked how you measured those differences?