Immersion heater/boiler - how to optimally use on single rate electricity tariff?

Vergo777

3 of us have recently moved into a rented flat which is electricity only. In previous places we had a combi-boiler which heated water on demand for showering/taps etc. but in this place looks like we have an immersion heater/boiler which heats up water at specified times and then keeps it warm throughout the day. Specifically, we have a PulsaCoil Stainless 180, the manual is at: w_w_w.gledhill-spares.net/documents/PulsaCoil_Stainless_Manual.pdf

It seems like this particular heater is designed to work best with an Economy 7 tariff where all the heating would be done during the night at off-peak prices and it'd keep a flow of hot water throughout the day using that.

However in our case since we only have a single rate tariff I'm wondering if the current setting of heating during the night actually makes any sense or is it a waste of money? Would it make more sense to set it to heat for 2-3 hours early morning to have enough hot water ready for quick morning showers and then 2-3 hours again mid-day for evening showers + washing up etc? But then I'm not sure if that much time would actually be enough to heat up the whole tank.

So my main questions are:

1. Should we continue having the heating on from 12am-7am or is there something more optimal?
2. If yes, what exact times should we program it to come on for?
3. How long would it typically take to heat up the full 180L tank from cool? Does it make any difference that this seems to use a plate heat exchanger rather than just heat up the water that's meant to be used directly?

MRB

Vergo777 wrote: »

3 of us have recently moved into a rented flat which is electricity only. In previous places we had a combi-boiler which heated water on demand for showering/taps etc. but in this place looks like we have an immersion heater/boiler which heats up water at specified times and then keeps it warm throughout the day. Specifically, we have a PulsaCoil Stainless 180, the manual is at: w_w_w.gledhill-spares.net/documents/PulsaCoil_Stainless_Manual.pdf

It seems like this particular heater is designed to work best with an Economy 7 tariff where all the heating would be done during the night at off-peak prices and it'd keep a flow of hot water throughout the day using that.

However in our case since we only have a single rate tariff I'm wondering if the current setting of heating during the night actually makes any sense or is it a waste of money? Would it make more sense to set it to heat for 2-3 hours early morning to have enough hot water ready for quick morning showers and then 2-3 hours again mid-day for evening showers + washing up etc? But then I'm not sure if that much time would actually be enough to heat up the whole tank.

So my main questions are:

1. Should we continue having the heating on from 12am-7am or is there something more optimal?
2. If yes, what exact times should we program it to come on for?
3. How long would it typically take to heat up the full 180L tank from cool? Does it make any difference that this seems to use a plate heat exchanger rather than just heat up the water that's meant to be used directly?

Without looking at your boiler specs, having had to research the one that was in the property I bought (leccy only) - a good, reasonably modern immersion boiler will keep the water at the right temperature for a long time.

If you're on a flat rate, you're best having it heat the water up at a time closest to when you all shower, that way you're using freshly heated water rather than water that may have had a couple of top up heats (albeit small amounts for a well insulated boiler).

Heating up water on demand is very expensive as it's basically getting passed through heating coils which is the same as running a bar radiator (if I recall).

I actually have mine on 24/7 heating, with the boost button deactivated (It's a holiday let) and it works out not that expensive at all. It's cheaper to keep water hot than it is to heat up cooled water.

Owain_Moneysaver

1. You probably won't need the full 7 hours heating, but the tank will have a thermostat so it will turn off once heated. As these are designed to keep sufficient heat for hot water all day you shouldn't need an afternoon top-up.

2. How is your time currently set? What sort of controller is there?

3. I'd expect 2-3 hours. The stored hot water will probably be at a higher temperature than would be expected in a normal cylinder but that doesn't directly make a difference to you.

Extra questions:

What sort of space heating do you have? An E7 tariff will probably be advantageous if you have storage heaters.

What sort of shower heads do you have? If there are 3 of you taking 2 showers a day each you could save quite a bit changing to a low flow shower head.

Gerry1

Why not just switch to Economy 7?

Vergo777

Owain_Moneysaver wrote: »

1. You probably won't need the full 7 hours heating, but the tank will have a thermostat so it will turn off once heated. As these are designed to keep sufficient heat for hot water all day you shouldn't need an afternoon top-up.

2. How is your time currently set? What sort of controller is there?

There is a controller which allows setting it to run in 3 phases. The previous tenants seem to have set it to run throughout the Economy 7 hours so this seems overkill. The controller allows us to run the bottom heating element for specific hours and also has a special boost button which runs just the top heating element to provide hot water quicker if needed.

Owain_Moneysaver wrote: »

3. I'd expect 2-3 hours. The stored hot water will probably be at a higher temperature than would be expected in a normal cylinder but that doesn't directly make a difference to you.

Does this mean if I just set it to run between 3am-7am it should be plenty to last for a quick morning shower and then an evening shower for everyone?

Owain_Moneysaver wrote: »

Extra questions:

What sort of space heating do you have? An E7 tariff will probably be advantageous if you have storage heaters.

We have electric radiators so Economy 7 probably wouldn't be much help.

Owain_Moneysaver wrote: »

What sort of shower heads do you have? If there are 3 of you taking 2 showers a day each you could save quite a bit changing to a low flow shower head.

Would love to do this but since it's a rented place not sure if the landlord would approve any messing about!

Gerry1 wrote: »

Why not just switch to Economy 7?

We're with Bulb who charge £120 to change meters so that would wipe out a lot of savings. Plus would have to get it approved by the landlord. Also if we have electric radiators rather than storage heaters I'm not sure if economy 7 would turn out to be much cheaper overall?

Owain_Moneysaver

Vergo777 wrote: »

Does this mean if I just set it to run between 3am-7am it should be plenty to last for a quick morning shower and then an evening shower for everyone?

Would love to do this but since it's a rented place not sure if the landlord would approve any messing about!

Should do.

You can get shower flow restrictors, they just screw onto the shower hose and then the existing head just screws back on.

https://www.victorianplumbing.co.uk/ultra-eco-flow-shower-flow-regulator-chrome-fr304

With that a 180 litre tank should give 30 minutes total of showering before needing reheated (or 6 x 5 minute showers).

matelodave

Get a flow restrictor as Owain suggests and learn to spend less time showering or take fewer showers so that that your hot water will last longer.

Everytime you run a hot tap, look at the amount of cold water that you waste before it gets hot and then consider that the same amount of hot water will then sit in the pipework and get cold. Rinse stuff in cold water (including your hands) and only use hot water when necessary.

Dont let hot water run down the sink, use a bowl or put the plug in the basin

macman

Gerry1 wrote: »

Why not just switch to Economy 7?

Because it's a rented flat, and the OP would have to bear the expense of rewiring and changing the metering, even if the LL agreed.
OP, remember that any heat escaping from the tank in winter is not wasted, as it serves to heat the property.

Gerry1

macman wrote: »

Because it's a rented flat, and the OP would have to bear the expense of rewiring and changing the metering, even if the LL agreed.

Not necessarily. They already have an immersion heater/boiler which heats up water and is set to E7 times, so it would only need a meter change. It seems some suppliers don't charge for this, Scottish Power being the most likely.

Theoretically they might have to change it back when then leave, but many suppliers will do this free of charge. It's not much of a problem anyway because many suppliers including Yorkshire Energy and Avro will happily just add the two readings together if you take a single rate tariff. They also tend to be competitive with relatively low usage at night.

doningtonphil

Hello
We are all electric and use an immersion heater to heat the water tank overnight. We were single rate and switched to octopus energy which offered a lower unit price than we previously had. Then spotted they have an agile tariff which needs a smart meter but the unit price changes every 30 mins through the day. Peak rate is tea time but overnight is between 3 and 5p per kwh. We are averaging about 10p kwh at the moment.

In fact, all parts of the day are a lower rate than octopus' standard tariff but 'tea time (1630-1900) is heavily weighted at between 20p and 30p per kwh

Can you switch supplier or are you stuck with bulb?

P.s. if you look at octopus and want to switch, let me know and I will give you a code where you get £50 credit on your account (as do I)