Will it be cheaper to use immersion to heat water now

coffeehound

One other thing you might consider is to reduce the thermostat setting in the IH to 55 C.  If that still gives you enough hot water then it reduces standing losses.  I should add that 60 is the number recommended by some authorities but I doubt there would be any problem at 55.

RG2015

coffeehound said:

One other thing you might consider is to reduce the thermostat setting in the IH to 55 C.  If that still gives you enough hot water then it reduces standing losses.  I should add that 60 is the number recommended by some authorities but I doubt there would be any problem at 55.

55 degrees? Aargh, Legionnaires!

coffeehound

RG2015 said:

coffeehound said:

One other thing you might consider is to reduce the thermostat setting in the IH to 55 C.  If that still gives you enough hot water then it reduces standing losses.  I should add that 60 is the number recommended by some authorities but I doubt there would be any problem at 55.

55 degrees? Aargh, Legionnaires!

Yes it's a point of contention, but 55 should be good enough IMO.  

In fact, in the USA the official advice is 120 ºF, which is only 49 ℃, though they do tend to have water heating running 24/7.  

Also, if your system is unvented, then the water remains chlorinated throughout anyway.  Personally I'd use whatever setting gives 53 ℃ measured (accurately) at the furthest tap. 

Edit, except in a new-build where all taps now need to have mixing valves to reduce HW temperature at point of use in bathrooms, etc.

Rodders53

If Kerosene is bought at even 190p/l = 19p/kWh or 21p at 90% boiler efficiency.
That's still (just) cheaper than electric at 22p/kWh.

My SVR with EOn is almost exactly 21p now and over 29p from April so oil would need to go higher still to make electric immersion heating more "economic" for me.

I'll use my A-A-heat pump to warm some rooms if oil remains over 85p/litre as I reckon that'll be the 'magic number' (assume a COP of 4 in heating mode) for 30p leccy.  I do so anyway at certain times of the year as UFH via the boiler is so 'laggy'.

RG2015

Browntoa said:

Rough estimate 

3kw immersion , 2 hours a day , around £500-600 a year 

6kw boiler , 2 hours a day , around £1000- 1100 a year

I follow the IH cost calculation of 3 kW x 2 hrs  x 365 days x £0.23 = £503.70.

However I am lost on the boiler calculation.

Using you figures, I get 6 kW x 2 hrs x 0.1 litre per kWh x 365 x £2.00 = £876

In addition, I am not sure if the 6 kWh for the IH is equivalent to 12 kWh for the boiler and £2 per litre for oil is very high. 

beefturnmail

Used to have my hot water come on for an hour in the morning and another hour in the evening.  Now changed to come in for just an hour every other day, been surprised about how long the water stays warm - could still have a hot shower the other day without it having heated up for 45 hours.

I have temporarily banned baths in the house though🤣 

lohr500

RG2015 said:

Browntoa said:

Rough estimate 

3kw immersion , 2 hours a day , around £500-600 a year 

6kw boiler , 2 hours a day , around £1000- 1100 a year

I follow the IH cost calculation of 3 kW x 2 hrs  x 365 days x £0.23 = £503.70.

However I am lost on the boiler calculation.

Using you figures, I get 6 kW x 2 hrs x 0.1 litre per kWh x 365 x £2.00 = £876

In addition, I am not sure if the 6 kWh for the IH is equivalent to 12 kWh for the boiler and £2 per litre for oil is very high. 

Bit unsure about this calculation as well.

An online tool I found suggests that to heat a 140 litre tank from 15 to 60 degC will take 1 hour with a 6kW heater.

The April EDF deemed tariff for my area is 27.1p/kWh, or 34.1/14.1 if on an Eco 7 tariff.
To heat the 140 litre tank once with electricity would cost £1.63 on a single rate tariff, or £0.85 using off-peak Eco 7. 
If I take the single rate, then £1.63 x 365 = £595 a year which agrees with Browntoa's calculation.

However, if 1 litre of kerosene has anergy equivalent of 10.35kWh and I assume a 90% boiler efficiency, then won't I need
 6/10.35/0.9 = 0.67 litres of fuel to provide my 6kWh? 

Today's price from the oil supplier who is usually the most competitive in my area is 129p per litre. 

1.29 x 0.67 x1.05(VAT) = £0.91 to heat the same 140 litres.

Even if the efficiency of the boiler fell to 70% due to heat loss in the pipework it would cost £1.12 which is still a lot less than using electricity.

I have a vested interest in looking at the calculation again, as last year I decided to switch from off peak electricity to oil for heating our hot water. I would now need to buy oil for £0.85 per litre to break even compared to our off peak electricity rate which is fixed to August 2023.

We have plenty of oil for the time being and my gut feel is it will drop back to below £0.85 in the next few months, so I'm going to keep using oil for now. 

I could be totally wrong though with the above calculations AND my gut feel on the oil price going forward!!!