Immersion or oil boiler

codo

Can anyone advise me if it is cheaper to heat my water in the summer by turning on the immersion or turning on the oil fueled boiler?

A friend has her boiler set to come on for half an hour in the morning and evening as someone told her this is the cheapest way of doing it. Can anyone confirm this as with the price of oil going so high Im not sure if this is still the case.

Thanks

paceinternet

"Cardew" has answered this many times in different ways. here is one of his last replies, but if your electricity isn't E7 and your normal rate is about 10p per kwh, then depending on your oil boiler efficiency, there isn't much in it.

"If your Immersion is heated on E7 you simply need to look at the price you pay for a kWh- around 4p. Electricity is 100% efficient so that is the cost.

The cost of oil depends on the price you pay for oil and the efficiency of your boiler.

A litre of oil contains 10.2 kWh, so approx 6.5p for a kWh at current prices around 65p/litre.

The efficiency of your boiler can be between 50% for an ancient boiler to 95% for the very latest condensing boiler.

So oil will cost anything between 7p to 13p for a kWh, with 10p being a reasonable average figure."

bobmedley

It's not as black and white as that - being on E7 usually gives you a punitive rate for other units consumed outside of the E7 period, so you have to take that into account.

Mazio_2

Some other things that could have an impact.
The distance from the boiler to the hot water tank. If it is an indirect system then your boiler would have to heat the water in the pipes normally 22mm from the boiler to then heat the coil in the hot water tank this distance could make your oil fired boiler even less efficient then that stated.

Can you regulate the hot water temp to about 60c easily as the immersion would do this.

One other thing to consider is your hot water tank lagged if not then this has a bearing on how long the immersion/boiler would have to keep toping up the heat if you are not using all the hot water immediately.

I have natural gas and I have found an immersion heater can actually be cheaper as I had an extension built and moved the boiler about 20ft away this has caused it to become very costly to heat my water in the summer. This however would not be the case if it was located nearer.

Cardew

I think with the cost of oil these days it is getting to the state where it is probably better to use an immersion heater for DHW in the summer(even if you are not on Economy 7), unless you have the very latest boiler in terms of efficiency.

As BobMedley points out above you pay a premium(around 2p/kWh?) for all daytime electricity if you have an E7 tariff. However I think that with oil CH it will be worth considering getting an E7 tariff and using it for DHW all year round.
Note: considering! you would need to do some calculations as there are several factors to consider.

codo

Thanks to you all for your advice.

I am paying about 10p/kwh of electricity. We have a very old boiler which probable isnt as efficient as it should be and is a distance away from the immersion so I think I will continue to use my immersion as there doesnt seem to be much in it.

Thanks Again

bobmedley

Cardew wrote: »

I think with the cost of oil these days it is getting to the state where it is probably better to use an immersion heater for DHW in the summer(even if you are not on Economy 7), unless you have the very latest boiler in terms of efficiency.

As BobMedley points out above you pay a premium(around 2p/kWh?) for all daytime electricity if you have an E7 tariff. However I think that with oil CH it will be worth considering getting an E7 tariff and using it for DHW all year round.
Note: considering! you would need to do some calculations as there are several factors to consider.

It has to be a very detailed calculation, as it is possible to move to E7 and it could actually cost you more than heating the water with normally priced electricity.

Best keeping the oil boiler going;)

Cardew

bobmedley wrote: »

It has to be a very detailed calculation, as it is possible to move to E7 and it could actually cost you more than heating the water with normally priced electricity.

Agreed,

The difficulty is getting the exact data to carry out that detailed calculation - e.g. boiler efficiency, how much energy(kWh) is used on DHW etc.

I changed from E7 to a normal tariff as it was not worthwhile with my consumption; albeit I have gas CH.

With my level of consumption at the time the 'break even' point was about 30% of my overall electricity to be used at E7 rates.

There are people who post on here(with gas) who can make E7 pay without using an immersion heater. Washing machine/dryer/dishwasher at night etc, or even if you get up early/go to bed late.

Certainly if you have oil CH(of any % efficiency) the 'break even' point where E7 becomes viable will reduce considerably.

If I had oil CH in my house I would certainly move to E7 and use it for all DHW.

No 'one size fits all' solution I am afraid.

Mazio_2

You also should consider oil/gas boilers are expensive when they break and running an electric immersion for say 4 months should help reduce the maintenance and extend the life of the boiler also. Immersions are say £14 to buy and fitting should not be to expensive.

bobmedley

OK, here is the appliance of science to see if E7 could work for me. I have an oil boiler that is 85% efficient, a 220 litre HW tank, my oil costs 64p a litre and I am with Atlantic currently with electricity at 10.36 per kw and E7 available at 5.06p and 12.19p. The mains water comes into the house at 16c (I measured it - how sad is that) & I will assume the temperature is 8c for 6 months. I will ignore any losses from the boiler pipe runs etc.

So, to raise the water temp from 16c to 60c for 220 litres takes 11.1kw x 183 days = 2,031kw

To raise the temp from 8c to 60c = 13.1kw x 182 days = 2,384kw

This means it takes 4,415kw to heat my water for a year (presuming the one tank is all I need per day)

Using oil at 7.38p per kw costs £326 and E7 £223 giving a saving of £103 p.a.

However, I use 10,000kw for the rest of my usage so I am penalised 1.83p per kw for the day rate giving a total of £183 ergo moving to E7 would cost me £80 p.a. extra. In fact, if I used full price electricity for the the HW it would still only be around £50 more than using the E7 tariff - it's hard to see how I could ever gain significant savings using E7.

Finally, there is also the question of flexibility - oil costs the same 24 hrs a day, whereas if you move to E7 and have to heat your water outside of the allotted period then it would have to be at the more expensive day rate making the economics even worse.

I'll get me coat...:p

bobmedley

codo wrote: »

Thanks to you all for your advice.

I am paying about 10p/kwh of electricity. We have a very old boiler which probable isnt as efficient as it should be and is a distance away from the immersion so I think I will continue to use my immersion as there doesnt seem to be much in it.

Thanks Again

You will only be saving money if your boiler is c63% efficient or lower - might be worthwhile using the model name/number to find out what it really is.