Hot water costs

macman

If I leave my central heating on 24 hours a day it uses more gas than just having it on 12 hours a day.

Amazing! And if I drive my car 100 miles it uses twice as much fuel as if I drive it 50 miles...

st999

But as I posted, if I leave my hot water on all the time it costs less than heating a tank of water, turning off the gas, using that hot water, then heating it up again.

macman

And as I posted, I suggest you are are incorrect.
This topic has been done to death in numerous previous posts and there's little that can be added if you can't accept why your claim cannot be correct.

st999

And as I posted, I suggest you are are incorrect

And I suggest that you are incorrect.

Prove me wrong.

You cannot because I have the figures that prove me correct

Cardew

st999 wrote: »

But as I posted, if I leave my hot water on all the time it costs less than heating a tank of water, turning off the gas, using that hot water, then heating it up again.

No it doesn't!!

It would defy the laws of physics for that to happen.

You have already seen the analogy of the kettle above - which you chose to ignore - which is perfectly valid.

So let us say that you leave your house for two years. Would it be cheaper to leave the hot water on all the time - because 'it costs less than heating a tank of water, turning off the gas, using that hot water, then heating it up again?'

For your principle to hold true it must cost less.

How about 1 year? A month? A week? A day? 12 hours? All exactly the same principle!!

If you don't believe the laws of physics apply then look up the Energy Saving Trust which covers this issue - and strangely does not agree with you.

Also seems strange that they have timers fitted for hot water heating - as if your theory holds true it would appear that having timers are more expensive.

If you believe that it is cheaper for you - then carry on. However to give patently incorrect advice to other readers is hardly money saving!!!

Incidentally why did you switch off the gas when you went on holiday for 14 days - if your theory applies, wouldn't it have been better to have left it on? Presumably you will for next year's holiday.

P.S.
Having said the above, the difference between leaving hot water heating on 24/7 and timed is not as great as many people believe.

A modern(foam) HW tank is tested to a British Standard and the average heat loss for a full tank of hot water at 65C is approx 2kWh to 3kWh in 24 hours.

st999

And if I drive my car 100 miles it uses twice as much fuel as if I drive it 50 miles...

That is incorrect as well, it all depends what speed you drive, whether you stop and start, how much fuel do you use crawling along for 50 miles stopping and starting then driving 100 miles at a constant speed.

Another incorrect assumption

IT ALL DEPENDS

st999

Once more

I left my house for 14 days with the gas turned off.

I came back at 1 pm and turned the gas on, the reading was 11802 cubic metres

Next day at 1 pm I read my meter and the reading was 11805. Difference 3 cubic metres = 34 kWh in 24 hours.

8 days later I read my meter and the reading was 11817 cubic metres a difference of 12 cubic metres = 137 kWh in 8 days which equal 17 kWh per day which is what my normal consumption is in the summer when my heating is off.

So explain that.

st999

Incidentally why did you switch off the gas when you went on holiday for 14 days

Would you leave a pilot light burning for 14 days with no one in the house?

Plus that would mean I was using gas when no one was in the house, not very money saving is it?

st999

A modern(foam) HW tank is tested to a British Standard and the average heat loss for a full tank of hot water at 65C is approx 2kWh to 3kWh in 24 hours

And my tank is insulated to that and also has an additional cylinder jacket.

When I went away for a week once the water was still warm, not hot, when I came back.

So if you take away the pilot light, 3 kWh per day and the losses say 2 kWh per day I am only actually using 12 kWh per day to heat my water. Less what the cooker uses, say 2 kWh per day, so this is getting interesting.

So 10 kWh per day for actual hot water constantly maintained at 60 deg C for a bath and a 10 min shower and washing dishes is quite good. So how did I use 34 kWh in one day to heat the tank of water up from cold?

macman

st999 wrote: »

Would you leave a pilot light burning for 14 days with no one in the house?

Plus that would mean I was using gas when no one was in the house, not very money saving is it?

D'oh! But that is exactly what you are doing by leaving the hot water on continuously.