Hot Water on all day or not?

sweetdaisy

At the moment I have the Hot Water (and Central Heating) to come on using the timer. So they are on for 1.5 hours in the morning and 3.5 hours in the evening.

I am currently at home during the day as I am on Maternity Leave, so using more hot water and sometimes heating during the day. Also we have two young children so we are using more water i.e. baths.

I have taken meter readings for both the gas and electricity this morning as I want to find out which is more economical:

1) Keep hot water as it is on a timer or
2) Keep hot water on constant throughout the day

For now, I have left the hot water and central heating on the timer and was thinking about doing this for 3 weeks, then take meter readings and do this again with the hot water on constant.

Just wondering is 3 weeks long enough to get a rough idea of how much more gas one method is using over the other, or should I test it for longer?

Thanks in advance.

macman

The answer is quite simple and doesn't take any weeks of tests. The longer it is on and calling for heat, the more gas it will use and the more it will cost.
Would you leave your kettle constantly on the boil to 'save the cost' of heating it from cold? Same principle.
Even with the timer on, it won't be heating unless the temp drops below the level set on the tank stat. However a well lagged hot water tank should stay hot for many hours, although there is of course some heat loss regardless.
Not quite sure of the relevance of the electricity meter readings?
If you do leave it on constant all day, switch it over to timed at night, as that's when the waste will be highest.

Cardew

This has been covered scores of times and without question it is cheaper to have hot water on timed.

In the same way it is cheaper to keep heating on timed.

However if you have a modern well lagged(foam) hot water tank, the heat loss is very low - about 2kWh in 24 hours with water at 65C. So as, even on timed, there will be hot water in your tank, the real loss is likely to be around 1kWh a day(say 4p) between having heating timed or on 24/7.

Even then that heat is not 'lost' as it warms the fabric of the house - which is why the tank is often in an airing cupboard.

sweetdaisy

Thanks for the advice. Our hot water tank is in the airing cupboard and is well lagged, so I will keep the hot water on a timer.

jalexa

sweetdaisy wrote: »

At the moment I have the Hot Water (and Central Heating) to come on using the timer. So they are on for 1.5 hours in the morning and 3.5 hours in the evening.

Does you system have seperate time settings for heating and water? About 1hr should be sufficient to reheat after a bath. Check if your "timer" is a programmer with a button to press for a 1hr heating period. If so you could save by having less timed control and pressing the 1hr water heating button before a bath is required.

As pointed out, if the cylinder is well lagged and/or you are making use of the drying cupboard, it's really not wasted heat. You will make much bigger savings by avoiding excessive or prolonged room temperatures.

sweetdaisy

jalexa wrote: »

Does you system have seperate time settings for heating and water? About 1hr should be sufficient to reheat after a bath. Check if your "timer" is a programmer with a button to press for a 1hr heating period. If so you could save by having less timed control and pressing the 1hr water heating button before a bath is required.

As pointed out, if the cylinder is well lagged and/or you are making use of the drying cupboard, it's really not wasted heat. You will make much bigger savings by avoiding excessive or prolonged room temperatures.

Thanks.

Yes, the heating and hot water can have seperate settings. At the moment I have the hot water and heating set for the same times:

6am - 7:30am and 5pm - 8:30pm.

I don't have a '1 hour heating/water button'. I didn't know it took an hour to heat up water for a bath. We use the bath once a night (to bathe the children) and the shower is used once in the evening too. We don't shower after 8pm because the children go to bed at 7pm and don't want to wake them, so technically I should just set the hot water timer until 7pm to save some money.

macman

It won't take 3.5 hrs to heat up the hot tank either. But of course any hot water you've run off will not be replaced by new if you reduce the evening cycle time.
Ideally you should have zero hot water left overnight to get maximum economy.
It will then reheat again come 6am.

Mr_Man_Full_of_Love

I have my hot water on all the time because my circumstances mean that I need it at random times with no set routine. It works out around £50 a year dearer but at less than a pound a week I think it's worth it.:)

It's a shame that no one has invented this mysterious kettle that gets trotted out every time, it could be a winner.:)

sweetdaisy

macman wrote: »

It won't take 3.5 hrs to heat up the hot tank either. But of course any hot water you've run off will not be replaced by new if you reduce the evening cycle time.
Ideally you should have zero hot water left overnight to get maximum economy.
It will then reheat again come 6am.

Thanks macman.

Cardew

Mr_Man_Full_of_Love wrote: »

I have my hot water on all the time because my circumstances mean that I need it at random times with no set routine. It works out around £50 a year dearer but at less than a pound a week I think it's worth it.:)

How do you work out a figure of £50 pa? - do you have gas?

oldskoo1

Are you sure you even need to heat it for that long as it stands now?

There are 4 in our house. Although we don't really take baths apart from the 3 year old, we all shower and i figured out, 15mins of water heating at 6am and 30mins at 6pm gives us all the hot water we need for the little ones bath, and our showers.

I think if you have appliances that need a hot water feed or perhaps things like power showers you probably need slightly more time. Check the thermostat on the hot water tank afaik the lowest safe temperature is 55C which is what ours it set to (or whatever the safest, lowest temp is). We store our winter/summer duvets in there + extra pillows and cushions so it's mega insulated.

I could knock that water heating time down to 15mins in the evening if the mrs would agree to a shared shower but that novelty died off long ago.