Electric immersion tanks

Dee_cb

Hi, I'm really sorry if there is already a thread about this. I live in a 1 bed room ground floor flat. I only have electric, my landlord told me to leave the immersion tank on all the time. I'm paying about £60 a month in electric. Can someone tell me if its cheaper to leave it on all the time or if I should keep it off untill about an hour before I need to do the washing up or when I need a shower?

Thanks for your help

Man_Overboard_2

Dee_cb wrote: »

Hi, I'm really sorry if there is already a thread about this. I live in a 1 bed room ground floor flat. I only have electric, my landlord told me to leave the immersion tank on all the time. I'm paying about £60 a month in electric. Can someone tell me if its cheaper to leave it on all the time or if I should keep it off untill about an hour before I need to do the washing up or when I need a shower?

Thanks for your help

Defo, switch it off when it is not needed. Shower less often, and use the kettle to heat up water for washing up.

Richie-from-the-Boro

Dee_cb wrote: »

Hi, I'm really sorry if there is already a thread about this. I live in a 1 bed room ground floor flat. I only have electric, my landlord told me to leave the immersion tank on all the time. I'm paying about £60 a month in electric. Can someone tell me if its cheaper to leave it on all the time or if I should keep it off until about an hour before I need to do the washing up or when I need a shower?

Thanks for your help

- when its on it costs
- when its off it doesn't cost
- treat it like a big kettle, that's exactly what it is

pamel

Find out whether it is on Economy 7.
If so then it will be on about 5 hours at night on lower rate electricity and it will turn off during the day anyway.
If you have Economy 7 then you have two dials on your electricity meter

Alternatively read the meter, leave the immersion on for 24 hours and read the meter again.
Then turn it off and just turn on when needed, read the meter straight away and then again after 24hours.
See what the difference is.
Make sure the two time periods are similar in that you are either in all day or same part of the day for proper comparison.

Be aware that it will take a while to reheat a whole tank from cold and if you only turn it on for a short while the hot water will be at the top from where it will be drawn when you use it.
However if you use the kettle for small amounts that will reduce how much you need to heat

[Deleted User]

if the stat on the tank is set correctly there is an argument that says its cheaper to leave it on,as you are then never heating a full tank from scratch

Cardew

It is quite clearly more expensive to leave it on 24/7.

However provided the tank is well insulated with a foam jacket, it won't cost a great deal extra.

Andy_WSM

Cardew wrote: »

It is quite clearly more expensive to leave it on 24/7.

However provided the tank is well insulated with a foam jacket, it won't cost a great deal extra.

To agree with Cardew & quantify that further. A well insulated tank will "lose" about 2-3kWh of energy in a 24 hour period, which in an all electric property the heat is "lost" to the surroundings, i.e heating the flat. So the actual "loss" this time of year from leaving the tank on is nothing as it's providing heat you'd pay the same rate for anyway.

cwalsh9695

To heat a tank from cold takes about 7KW hours about 90pence on current rates.
To leave the immersion on 24 hours, once it is up to temperature and the immersion cuts out, it will not start to heat up again until the temp has dropped by about 10 degrees.
So after a bath/shower you will spend 10-20 pence to heat it up again and during the day as the tank temp drops the immersion will kick in again ang again as the temp drops.
Being an Electrician I have come across this question many a time. The answer is about usage, if you use alot of water, leave it on.
Heating warm water is cheaper than heating from cold.
Low usage turn it off.
If you have night and day rate (night rate normally from 11pm till 7am).
Heat your water for 45 mins during the last hour.
The water will stay hot Most of the day.
If you shower in the evening, give it a quick blast for 15 mins. Should keep your costs under a £1 per day

One for yourself!

Richie-from-the-Boro

Assuming a non-E7 tariff.

The O/P's described use was """washing up or a shower""" whichever way you debate UFactors or thermal insulation, leaving it on 24/7 throughout the year is madness.

An immersion element will give a maximum of the 25% of a cylinder, that in turn will be cooled only to be reheated by convection, that constant cycle of cost to heat and cost to reheat again is caused by a convection current. Liquid, such as water, is heated from the bottom, the layer of water closer to the heat source expands and hence becomes less dense compared to the water layer above it. Expanded water is less dense than the surrounding water and therefore it rises. The cooler regions of the water in the upper part of the flask, being denser, sink. This movement of liquid due to a difference in density sets up a convection current.

So the heated [ hot ] water pushes up and forces the cooler water down over the thermostat which in turn is heated until the whole volume of the tank reaches your pre determined setting then the stat switches the leccy off. Its a bit atomic science and the random motion of atoms and all that, but sufficient to say that's why the top / immersion element is rubbish at heating water. The argument saying its cheaper to leave on has no science behind it no matter how well insulated it was. The only exception to that rule would be the 'lifestyle' one. If the tank was (1) oversize (2) uber insulated and a (3) bottom stat & element and (4) a family with 4 kids each wanting a bath / shower every night of the year with a family of 6 hot water needs and able and willing to afford the cost - that would be an exception.

grahamc2003

woodbine wrote: »

if the stat on the tank is set correctly there is an argument that says its cheaper to leave it on,as you are then never heating a full tank from scratch

I suppose some would argue that, but I'm afraid such an argument is total nonsense.

macman

Your landlord is clueless. Fit a timer and put it on for a couple of hours (early in the morning during cheap rate if you are on E7).
If the tank is properly lagged it will keep warm all day.