is it cheaper to have the boiler on the eco setting even though we need to waste h20

tamyoung

Myself and boyfriend are having a big argument about the below and hoped someone could help out.
We have a modern condensing gas boiler (british gas) and it used for heating the water for the washing up - that is pretty much all (we have an electric shower, and wood burners for heating). The boiler has 2 settings Normal and Eco.
Normal means you get hot water in about the time it takes to run 1 normal sized washing up bowl.
Eco means it may take 2.5 bowls.
We are on a water meter in South West (water costs about 4pounds per cubic meter)
We wash up once a day. 3 at the weekend.
So the question:
Taking into account the cost of the water that gets wasted by waiting for it to heat up when on the eco setting, is it cheaper to have the boiler on Normal all the time so when we do the washing up we use less water, on the Eco setting thus saving gas (but wasting more water).

This does sound a bit like a maths GCSE question with a few bits missing!!

Mankysteve

right you need to take the number of litres your washing bowl holds and dived by 1000 to get cubic meters. then multiply that by your cost per litre
My washing up bowl is 10 litres so
10/1000=0.01cm2
0.01*£4(cost per litre)=0.04p a bowl.

The next step is to record you gas usage in normally and eco mode.
Choose a time at say 7pm make a note of your gas reading, run the boiler on eco mode then 24 hours later take another gas reading. This will give you units you've used.

Do the same the next day with boiler in normally mode.

If your cooking on gas try as much as possible to match the cooker loads as much as possible, Or use a longer time period and divide the amount used by the number of days to average out fluctuations due to the cooker cooker.

Calculate the cost of the gas you've used

number of units(times by 2.83 if you have an imperial meter)*39.7(Typical Calorific value)*1.022640(Correction factor)then dived all that 3.6 to give you Kwh. Check your supplier for the cost per Kwh

Ie say in eco mode you use 2 units and 3 units(a day) in normally then

2*39.7= 79.4
79.4*1.022640=81.197616
81.197616/3.6=22.55Kwh

22.55Kwh *3.807= 85p a day

3*39.7=119.1
119.1*1.022640=121.796424
121.796424/3.6
33.83kwh
33.83*3.807=£1.28

increase = 1.28-0.85 = 43p increase

So from the calculation above about cost per a bowl. 2.5*0.04=0.10p cost per a wash for eco mode so it cost 10p-4p=6p increase of water per a wash

While the increase cost per a day on normally mode is 43p thus in this example its cheaper to run in eco mode.

But you need to do your own sums on
1. Cost per a bowl
2. Cost of gas usage per a day in each mode
3. the difference between them. if the increase in use of gas in normally is greater than the cost of increase in water of eco mode then Eco mode is cheaper.

bockster

i think you have to look at the 'normal' mode as a convenience feature that you will pay for and doubt it can be more efficient for most people most of the time.

my tip, maybe you allready do this, when running the hot tap and waiting for it to become hot, only turn it on just enough to kick the boiler in. once it starts to come though warm then turn your tap on full.

the initial slow flow allows the heatexchanger to reach operating temperature whilst wasting as little water as possible.

hth
bockster

Mankysteve

I did forget to add that Eco will more than likely cheaper

TheOne

If you need to run alot of water before it gets hot, I believe there are water saving devices you can get to fit to your drainage system, so you can divert the water down another route (another pipe to an outside water but for example). Not sure what they are or where you can get them from, but I have heard of them.

Cardew

Isn't there a clue here - let me think - Eco? Nah couldn't be that could it?

Jamesro_2

Yeah thanks Cardew, really good point really well made!!
'Yeah coz it sayz ECO on it, it most definitely is way much cheaperer!'
I think the point trying to be put across is: Is the saving from running the boiler on Eco offset by the cold water that is wasted by waiting for it to be heated up to temp.
Would have thought a bit better from a 'Deliciously Dedicated Doubly Diehard MoneySaving Devotee'