Oil vs Immersion

Gwynston

Now that it's a bit warmer and we don't need the central heating on, I've just set the oil-fired boiler to come on for an hour in the morning and evening to heat up the hot water tank.

The high price of oil got me to thinking about whether using the electric immersion heater on the water tank might be cheaper. Traditionally, I'd always been led to think the the immersion heater uses a lot of electricity, but I wonder if it's more competitive now, just for an hour or two every day. Of course, I'd have to fork out a few quid for timer switch.

In England we used to have a house with only electric heating - storage heaters and immersion that used cheap-rate electricity at night. Was good value, but a pain when you ran out of hot water or needed to put the heaters on during the evening if they'd gone cold.

Sparky

It will be cost effective if you have a good lagged cylinder and a decent thermostat.
The most amount of energy used will be in getting the water up to the setting you have the thermostat at (normally 60+).
After that if the heat stays in the need for the thermostat to kick in will be less that if the cylinder was'nt lagged.

If your going to get a time switch get a Flash immersion time switch from an electrical wholesalers ~€25, as you will pay loads in the likes of woodies etc.

Unless your going for an electronic 7 day timer, which will cost more.

Also make sure your house has an ESB night saver meter as the rate is cut by a third at night time.

Lex Luthor

I've always thought about this too....I switch off my heating completely from about mid May to mid Sep and use a 7 day 24hr timer on my immersion to heat the water in it. I never really calculated which was cheaper but I just hate to have the heating on in the summer, even though I could manually turn all the rad valves off.

Alun

All you need to do is to turn down your thermostat so that the heating never comes on, but the hot water tank is still heated. No need to go turning all the radiators off. Which is more expensive though ... no idea!

JamesM

Alun wrote:

All you need to do is to turn down your thermostat so that the heating never comes on, but the hot water tank is still heated. No need to go turning all the radiators off. Which is more expensive though ... no idea!

It depends on the system ! You can't always do that.

On the original question - It used be cheaper to use the oil. I used to find that you would barely see the level in the oil tank change over the summer. I think that if you have a modern boiler in, or very close to, the house, you will find it OK.
Jim.

Alun

JamesM wrote:

It depends on the system ! You can't always do that.

Yeah, sorry about that. I assumed everybody had the same crappy old-fashioned setup I'm saddled with at the moment

JamesM

Alun wrote:

Yeah, sorry about that. I assumed everybody had the same crappy old-fashioned setup I'm saddled with at the moment

Your system is more sophisticated than those where you can't turn down the stat to shut off the rads and still heat your water:D
Jim.

Lex Luthor

If I was to use my oil heating for my hot water I'd have to switch off each rad manually. Not a big problem. 5 mins tops.

So do you really think it would be cheaper to heat the immersion from the oil?

Only problem I have is the stat timer that controls my heating is only switchable on/off in 1hr intervals....but the one I have on my immersion is controllable down to the min.

I find the 1hr interval fine when using it for heating the house, but for immersion only its not necessary to have it on for 1hr when 40 mins would be enough to heat up the immersion.

JamesM

Lex Luthor wrote:

If I was to use my oil heating for my hot water I'd have to switch off each rad manually. Not a big problem. 5 mins tops.

So do you really think it would be cheaper to heat the immersion from the oil?

Only problem I have is the stat timer that controls my heating is only switchable on/off in 1hr intervals....but the one I have on my immersion is controllable down to the min.

I find the 1hr interval fine when using it for heating the house, but for immersion only its not necessary to have it on for 1hr when 40 mins would be enough to heat up the immersion.

In the late 70s and into the 80s, I found people who were using 3 times more electricity in the summer than the winter. My oil level was barely changing. Oil is dearer now, but the also boilers are more efficient.

Lex, If your boiler has heated a full hot water cylinder in 40 mins, the boiler thermostat will keep the burner off for most of the last 20 mins of your hour.
If your burner runs for a full hour without stopping, it will use about 1/2 gallon of oil. If you are only heating the water, you will find that it is not running for a good amount of that time. It will run for about 10 mins and then cycle on and off for the rest of the time, and usually off more than on.
Jim.

Gwynston

Sparky-s wrote:

It will be cost effective if you have a good lagged cylinder and a decent thermostat.

Well, the house is only 5 years old and so the boiler should have a decent thermostat. It is the modern kind with the stuck-on solid foam lagging.

Sparky-s wrote:

Also make sure your house has an ESB night saver meter as the rate is cut by a third at night time.

What do I need to do to get this? Does it cost me money to get it fitted?

Reyman

If you're going to sign up for night rate you need to do your sums:

There is a standard yearly charge of €114.12 if you sign up for it - Equivalent to about 900 units at the high rate

Day rates are €0.1273 per unit (kw.hr)
Night rates are €0.616 per unit.
(Add 13.5% VAT to all rates)

You need to be using a lot of electricity at night (12.00pm - 9.00 am summer) to cancel out the fixed charge.
eg. storage heater, washing machine, dishwasher.

With just water heating you're probably going to lose money.

gonk

The Sustainable Energy Ireland website fuel comparison page gives a VAT-inclusive cost (at January 2006 prices) of 8.27 cents per kilowatt/hour equivalent for a kerosene fuelled boiler, assuming 70% boiler efficiency.

(http://www.sei.ie/index.asp?locID=138&docID=-1)

Night rate electricity costs 6.99 cents per kWh - including VAT - or 1.27 cents less.

The annual standing charge is €114.12 plus VAT for the ESB Nightsaver tariff, but their standard standing charge is €65.04, so the extra cost is only €49.08 per annum, or €55.71 including VAT. (These are at the urban rates - there are higher rates for rural customers.)

So, to justify the extra standing charge, you'd need to be using at least about 4,400 kWh of electricity at night rate, compared to heating water with oil. This doesn't take account of whatever once-off charge the ESB might make (if anything) for changing your meter to the night rate version.

Reyman

Thanks Gonk:

I forgot that standard ordinary charge of €65.04. That makes the night rate extra charge easier to justify.

dingding

The ESB don't charge to install the meter but you have to kep it for a month.

the times are 11pm to 8am in the winter and midnight to 9am summertime.

If you use your dishwasher, washing machine, tumble dryer and electrically heated power shower you should have good savings. I save 20 - 30 euro a month with it.

Gwynston

In order to run all those machines at night, I'd need a timer switch on each of them, which would be a good few Euro's upfront though.

gonk

Gwynston wrote:

In order to run all those machines at night, I'd need a timer switch on each of them, which would be a good few Euro's upfront though.

Not really - you can get a 3-pack of 24 hour plug-in timers from Woodies for €12.99. Your 1st month's savings would almost certainly cover that.

http://www.woodiesdiy.com/shopping.aspx?loc=C&catid=6.7.2