Electric Alternative to Immersion Hot Water

Fyne

We have an Ariston Primo 200l unvented immersion cylinder, 3w + 3w. We are an electric only house with no access to gas. The householder before left the immersion on 24/7 and we have continued to do the same. We have an electric shower and almost never have a bath, so we use little hot water. Would an instant hot water heater be a good replacement, we need hot water in kitchen and 2 bathrooms. Oh, should add we are on the Total Heating Total Control tariff with SSE, getting 24/7 cheapish rate for underfloor heating, hot water and towel rails.
Any advice on alternatives to the massive cylinder appreciated.

FelineFunk

Fyne wrote: »

We have an Ariston Primo 200l unvented immersion cylinder, 3w + 3w. We are an electric only house with no access to gas. The householder before left the immersion on 24/7 and we have continued to do the same. We have an electric shower and almost never have a bath, so we use little hot water. Would an instant hot water heater be a good replacement, we need hot water in kitchen and 2 bathrooms. Oh, should add we are on the Total Heating Total Control tariff with SSE, getting 24/7 cheapish rate for underfloor heating, hot water and towel rails.
Any advice on alternatives to the massive cylinder appreciated.

A kettle?
Or, as you suggest, an electricly powered, instant hot water heater.

Of course, a kettle (and probably an instant hot water heater) would use top rate electricity, rather than the cheap rate probably used to heat the water in the "massive cylinder".

But if the aim is to remove the hot water cylinder, irrespective of cost ... :cool:

coffeehound

Ariston quote about 2 kWh daily loss for this size of their current hot water cylinder, so if you cost that using your current kWh unit price, it shows the worst-case cost of having an unused tank of water for a day. I'm guessing that is small compared with the expense of buying and installing a new heater system.

Also that heat isn't wasted as such; in colder weather it contributes towards the home heating in the same way as your other heating sources.

Are you just using the upper immersion heater at present? This would make sense for limited hot water requirements. Also have you checked that the elements' thermostats are set to 60 degrees?

Your current system gives you good flexibility for varying requirements for if you have visitors, etc. I would stay with it.

ETA: If not already done, you might consider insulating the hot water pipes where accessible.

.

AndyPK

do tell me.


Do you have a switch each, for each 3KW immersion?


What I would do.


1) turn off the bottom immersion. See if that gives you sufficent hW for your needs.
2) buy a timer, About £55 for timeguard. connect up to the primary heater you wish to use. set for 1 hour in morning, 1 hour in evening.
Some have a boost function, and this could be connected to the other immersion

Fyne

Thanks for your advice, will look to install a timer and switch the bottom thermostat off and see how that goes. Space is not the issue.

jk0

Isn't the lower immersion controlled by a switch in the meter though? A timeswitch won't work properly if you connect it to that supply.


Nor will putting a timeswitch on the top immersion save you any money compared with leaving things alone, if the top immersion consumption is at a higher cost per kwh than the lower immersion.

coffeehound

jk0 wrote: »

Isn't the lower immersion controlled by a switch in the meter though? A timeswitch won't work properly if you connect it to that supply.

Nor will putting a timeswitch on the top immersion save you any money compared with leaving things alone, if the top immersion consumption is at a higher cost per kwh than the lower immersion.

That's a good point. I'd assumed all water heating would be on the 24/7 cheap rate but perhaps the top element isn't. Worth the OP checking.

Would there be any need for a meter-controlled contactor when the reduced rate is 24/7 though?

Fyne, can I ask what your unit prices are?

AndyPK

The way I read it the op did not have E7, but a flat tariff


"Oh, should add we are on the Total Heating Total Control tariff with SSE, getting 24/7 cheapish rate for underfloor heating, hot water and towel rails."

Fyne

Daily standing charge - 25.81p
Standard cost per kw - 18.76p
THTC cost per kw - 12.94p

Will need to check if both top and bottom immersions are on the THTC meter, which is flat tariff 24 hours a day

coffeehound

Thanks. Rough calculation: if each of three instantaneous heaters cost £250 to buy and install (at a guess, could well be more) = £750.

Compare that with the top immersion being run full time on low rate, and assuming the tank then lost 1.5 kWh per day = 13p x 1.5 x 365 = ~£70/year in 'losses'.

So around a decade to break even on the cost of installing the individual instant heat units in that case. The instant heaters might save a little more in water and lack of hot water left sitting in pipes. But also the heat from the big cylinder isn't wasted for most of the year, as said.

ProDave

Fyne wrote: »

Daily standing charge - 25.81p
Standard cost per kw - 18.76p
THTC cost per kw - 12.94p

Will need to check if both top and bottom immersions are on the THTC meter, which is flat tariff 24 hours a day

That is a legacy tariff that is VERY expensive.

By way of comparison my standard tariff for single rate electricity with Octopus is 14.8p per unit.

you would have to use a LOT of the THTC units that are less than 2p cheaper to make up for any standard rate units you use that are nearly 4p dearer.

If you use storage heaters, switch to Economy 7 or even economy 10 and shop around for the best deal. You are stuck with SSE as long as you stay on THTC