Turn off Hot Water Tank to save money?

THEV1LL4N

Can I save on my bills if I switch the hot water tank off when it's not in use? For instance, if I go away for a long weekend (3 days) or for a week or two?

Not too sure on how hot water tanks work, if they are constantly being heated and whether or not turning it off and switching it back on again will save energy for the duration it's not in use, or consume a lot of energy to heat the entire water tank back up again.

Would it be saving me anything if I turn the hot water option off from the hot water and heating control in the downstairs kitchen, or would I need to reduce the temperature (essentially switching the tank heating off) from the tank itself?

Hoping for some insightful responses if others do the same.

Thank you. 

macman

Is this an all-electric system with an immersion heater?
If so, the cheapest option is to heat it using a timer when you need it. If E7, you want to heat it during off peak hours. If not, the maybe an hour early morning and early evening?
Why on earth would you leave it on for a week if you are away? It's thermostatic, but will then cycle on and off as it loses heat from the tank.
Dropping the 'stat setting on the tank doesnt' turn it off, it just lowers the target temp

[Deleted User]

I'll assume a system boiler and hot water tank - rather than all-electric (because that's what I have).

Yes, it would save you a little bit.  They're not constantly being heated, unless you have your hot water option turned on 24/7 without any sort of timer, and even then it would be running on the tank thermostat.  You probably have it turned on for several hours a day, not 24/7.

The heat loss across three days from an unused hot water tank is slightly less than three times the daily heat loss.  But not by a huge amount.

Alnat1

What do you use the hot water for? Is it mostly for showers and if so, how many a day and when?

We are a 2 person household and heat our tank (using a timer) for 40 minutes in the morning because this is when we shower. This is enough for 2 showers and a bit left. If either of us wants a bath, we switch it on manually for 15 mins extra.

No point paying to heat water you won't use. If your shower is electric, no point heating the tank at all, boil a kettle for any hot water you need.

FreeBear

Alnat1 said: No point paying to heat water you won't use. If your shower is electric, no point heating the tank at all, boil a kettle for any hot water you need.

This is what I do during the summer months. Just fire up the boiler for an hour with the tank thermostat set to 45-50°C when I need a tank of hot water. Boil a kettle when I need a smaller amount for washing up.

Immersion heater had the fuse taken out years ago to prevent it from being "accidentally" turned on.

Mstty

I wonder how many other people dont know how their hot water works and how to adjust it.

jadey2024

I'm all electric E7. I don't put the tank on for hot water. We have electric showers and not every day, never have baths and just use kettle or something to wash up once a day. It is just a waste of money putting it on even in off peak every night and most the water won't get used up.

I occasionally put the tank on every few months just to make sure it is working and heating up okay especially as I'm renting but that's it.

Coffeekup

Mstty said:

I wonder how many other people dont know how their hot water works and how to adjust it.

Judging by the posts over the last few months, a good number of people.

sparky0138

Alnat1 said:

No point paying to heat water you won't use. If your shower is electric, no point heating the tank at all, boil a kettle for any hot water you need.

We only use ours for washing up and heat the tank for a total of 40 minutes every day. It's only just occurred to me after reading another thread that we're wasting money and have been doing this for nearly 5 years!

If my calculations are correct, we could be saving £145 per year on our current tariff and approximately £380 when it ends, just by boiling the kettle a couple of times per day instead.

Does anyone know please, are there any implications of not heating the tank? And should we turn the water supply off too or keep using the "hot" tap to keep the water flowing through the system. Bit concerned about water storage and Legionella. Thanks.

FreeBear

sparky0138 said: Does anyone know please, are there any implications of not heating the tank? And should we turn the water supply off too or keep using the "hot" tap to keep the water flowing through the system. Bit concerned about water storage and Legionella. Thanks.

During the summer months, I don't bother heating a tank of water unless I want a bath. Even during winter, I don't have the system set to specifically heat the tank unless it is bath night. A kettle & electric shower is sufficient for much of the time.

Legionella is a very small risk in this country. Some 250 cases reported annually. Having an uncovered cold water storage tank with birds flying around will increase the risk, but most people will have a covered tank in the loft (so no birds). If you do have any concerns about disease, heat your tank to ~55°C for a couple of hours once a week. At 60°C, bacteria will be killed within minutes. At 55°C, legionella bacteria will be killed in an hour or so.

If you have a combi boiler, none of the above should matter - The incoming water will have been treated, and it doesn't sit around in the pipes long enough for bacteria to breed.

[Deleted User]

Legionella is a very small risk in this country

Arguably, so is Scarlet Fever which is in the news at the moment. I would say that it is a given that if people stop heating their hot water cylinders there will be an increase in Legionella infections. The risk is magnified if there is very little water flow.