# Cheapest way to Have shower?



## roadrunner (15 Sep 2008)

A. Turn on Immersion
B. Have an electric shower
c. Heat with Oil

Well folks anyone done the maths?


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## Happy_Harry (15 Sep 2008)

Never done the maths, but I am sure it is the electric shower, as you are only heating the water you need for the shower. With the other options you'll heat more water than you'll need. Obvious assumption is that you have all 3 options available, so no investment is required.


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## sydthebeat (16 Sep 2008)

roadrunner said:


> A. Turn on Immersion
> B. Have an electric shower
> c. Heat with Oil
> 
> Well folks anyone done the maths?


 
a + b use the same fuel so unit cost is the same, however the electric shower is used 'on demand' thus the minimal energy is used. If the same shower is to be heated by the immersion, there will always be excess heated water left over... thus the electric shower is the cheapest.

option C has the same issues as A. No way of equating quanity of energy to actual usage.


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## ClubMan (16 Sep 2008)

Have a cold shower?


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## Cheeus (16 Sep 2008)

What about electric shower versus shower with instant hot water via gas?


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## davidoco (16 Sep 2008)

from http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1752

Obviously nobody disagreed with Ted!

Personnaly I'd go with the Immersion because there is nothing worse that going into the bathroom or kitchen and having no warm (or hot) water at the tap. Get the timer on the immersion right and you would have 100% efficency heated water with hopefully a little to spare for the taps.

*************************************

Water tank - 100 litres
Start water temp - 20C
End water temp - 65C

You need 1000 calories to raise the temp of 1 litre of water by 1C

So 1,000 x 100 x 45 = 4,500,000 calories

4,500,000 x 4.2 = 18,900,000 Joules

So, in this example, we need this amount of energy from either oil or electricity.

This is the energy required but over a period of time.

If it took, say, 157.5 minutes to heat the water then the power used would be:

18,900,000 / (157.5 x 60) = 2,000 Joules per second

This happens to be equal to 2,000 Watts (the rating of your immersion heater).

2 kWatts x (157.5 / 60) = 5.25 kWh 

So the cost of electric consumed at 11p per unit is:

5.25 x 11 = 57.75p

To get 18.9 MJoules from heating oil (approx 35 MJoules/litre) would require:

18.9 / 35 = 0.54 litre if burnt at 100% efficiency.

If your efficiency is only 60% then your actual oil use would be:

0.54 x (100/60) = 0.90 litre

If your oil cost 60p per litre * then the oil cost would be:

0.9 x 60 = 54p


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## DavyJones (16 Sep 2008)

Good post david, how miuch energy did it take to come up with that?

I always use my oil burner to heat cylinder and have a power shower. I really don't mind if it costs a few pence extra, I feel I'm worth it.


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## davidoco (16 Sep 2008)

DavyJones said:


> Good post david,


 
Before I get in trouble the calcs are Teds. The most interesting part of his cals for me is 

If your efficiency is only 60% then your actual oil use would be:0.54 cost per litre x (100/60) = 0.90 litre

In Irish terms with oil costing say .80 cent per litre an efficiency table would be the following

1 litre of oil would give 10 kilowatt-hour at 100% efficiency.
[broken link removed]


So from reading the above (if I am correct) Oil is always cheaper than electricity and if your oil burner is inefficient you could be paying twice the price for your oil that you need be with proper servicing although most standard oil boilers would at best run between 80% and 90%.


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## roadrunner (16 Sep 2008)

Some thorough answers there! How much more efficient are the condenser boilers.


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## DavyJones (16 Sep 2008)

roadrunner said:


> Some thorough answers there! How much more efficient are the condenser boilers.



91% +

Make sure and get it commissioned right.


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## badabing (17 Sep 2008)

roadrunner said:


> Some thorough answers there! How much more efficient are the condenser boilers.



Trouble is with condenser boilers, they have to start u heat themselves, heat the pipes, suffer pipe losses as all other boilers do, so budget for around 50%  system efficiency regardless og boiler type. The electric option is as cheap, but gets well cheaper if you have a night rate meter which is 40% full rate


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## Leo (18 Sep 2008)

Now, I don't want to be the humour police, but can we try and keep this on-topic? Some good responses here were getting lost in the multitude of 'use someone else's' suggestions.
Leo


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## loukkcat (26 Jul 2010)

Hope nobody minds me re-igniting this post!!

Have just got my second pretty high electricity bill (considering it's summer) from Airtricity. 

As we are rarely in the house in summer and don't feel we use much electricity, except for to have showers, dishwasher and washing machine, can't really figure it out. 

Only conclusion is that using electric shower or immersion is costing a lot more than using gas was in the winter...could this be so? and which is cheaper? We have  been using the electric shower more than the immersion because we thought this was cheaper, but would be better off using the immersion? 

Can anyone think of anything else that could be eating electricity in the summer months?


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## AlbacoreA (26 Jul 2010)

I got our heating rewired so I can heat the hot water cylinder separate to the radiators. Can you do that? Maybe put a timer on people using the shower? The dishwasher is another thing you could use less.


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## chrisboy (26 Jul 2010)

loukkcat said:


> Hope nobody minds me re-igniting this post!!
> 
> Have just got my second pretty high electricity bill (considering it's summer) from Airtricity.
> 
> ...



Bills could be estimated rather than actual readings..


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## Leo (26 Jul 2010)

As Chrisboy points out, first step is to make sure your bills are based on accurate readings. 

Yes, electricity will cost more than gas to heat water. Using the immersion to heat water will likely heat more than you need, so the electric shower would be better there.


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## loukkcat (26 Jul 2010)

Meter was read at the end of June, so just July was an estimate. 

Electric shower is what we have been using 90% of the time since we turned gas off in April.


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## niceoneted (26 Jul 2010)

I would look at all the other electrics in the house. Are you leaving things plugged in/turned on, lights etc. 
My bill is considerable less than the winter and more showers are being had - before and after work it's so warm.


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## Marietta (26 Jul 2010)

niceoneted said:


> My bill is considerable less than the winter and more showers are being had - before and after work it's so warm.


 

What part of the world are you in?? I had the heating on over the weekend


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## niceoneted (26 Jul 2010)

Ire, slightly west of Dublin. 
You need to get moving or put an extra layer on!! I haven't had the heating on since April I think.


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## Marietta (26 Jul 2010)

Ha, you are right I am always cold but have a warm heart!
I use the oil all the time to heat the water. I time it to come on for a half an hour, I never use the immersion.


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## theresa1 (26 Jul 2010)

A shower every second day is the way to go -certainly not one in the morning and then the evening.


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## Marietta (26 Jul 2010)

I could never start the day without a shower, I just wouldnt feel right.


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## fizzelina (27 Jul 2010)

I use the gas heating to heat the water, set for 3 hours a day, it's possible to heat water separately without having gas on in radiators. I think 3 hours is too long for just 1 couple to have a shower each? Also is this a cheaper option than turning on the immersion? How long would people keep the immersion on for a couple of showers a day.


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## dubgem (27 Jul 2010)

I have gas central heating and an instant shower.  

In the winter the central heating also heats the water coming out of the taps, so you can use it for washing up and you don't freeze your fingers off every time you wash your hands.  My house has terrific insulation so in the morning it is warm enough for getting up and out, and the water in the tap is still hot enough for hand washing etc. without the heating coming on again.  (On weekends we usually put it on for an hour or two about 10am to keep the warmth going).

In the summer the water coming out of the taps is cool, but not so cold it's uncomfortable to wash your hands with it.  For washing-up I boil a kettle.  And I still have hot showers from my instant shower.

So adding it all up year-round, the instant shower is definitely the best way to go.


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## hfp (27 Jul 2010)

looking at the efficiency calculations above scared me!!  mines a modern gas combi boiler, with piped gas, last time the boiler efficiency was measured during a service it came out at 85%, not the 50-60% quoted above.  I get instant hot water whenever I want, and the shower is nice and powerful.  don't know how it compares financially to other types but I love it!! had oil heating in my parents house and hated that we always ran out of water, or couldn't have a shower without having to wait an hour for the heating.

have absolutely no facts and figures to back it up, but I always thought that an electric shower was fairly inefficient due to using an electric element?


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