Electric water heating tank - best to leave on all the time?

BexInLondon · 28 May 2009 at 4:20PM

Hi,

Recently moved into a new build, and like all the others we look at, it has no gas. Quite apart from the devastatung impact on my cooking, it means our water heating is electric. It's a massive (7-foot tall and about 2 foot diameter) tank in the airing cupboard. Basically it gets heated, then when we run the hot tap water runs past the pipes and is in turn heated... or something like that....

Anyway, I've not yet had an electricity bill and not yet got a key to the meter cupboard so no idea whether we're absolutely caning the elctricity with this thing. It had a faulty pump when we first moved in and the engineer who came out said it was cheaper/same to leave it on al the time rather than have it just come on for a couple of hours off-peak.

Does anyone know if he is right about this?

FYI it only runs hot water, not central heating, which is provided by stupid electric radiators.

FFYI there are only two of us in the flat, but it has 3 bedrooms and 3 bathrooms.

TEDDYRUKSPIN · 28 May 2009 at 4:49PM

Ooooo. You have the new systems in place? Exciting! Cooking affected? It will actually be the hob as many companies now release brilliant electrical hobs which are as hot as gas hobs. Brilliant for chinese and indian cooking.

Back to the question..... do you need to keep this on? Supposedly no. No harm in leaving it on and no harm in leaving it off.

I myself would just switch it off. The standby light alone drains electricity.

AdrianW2 · 28 May 2009 at 5:16PM

It always takes energy to keep anything hotter than the ambient temperature. Whether the cost is significant depends on the quality of insulation in the tank, but in general there's no reason to keep the heater on if you don't need to.

I can't see any reason to have a large water storage heater unless you're on Economy 7, in which case it is almost certainly cheaper to run it at night only.

Are you sure your tank isn't something like a Megaflow and directly heating the water?

BexInLondon · 28 May 2009 at 5:23PM

Hmmm.... the tank is fairly well insulated - i.e. feels ambient to the touch rather than hot, but the pipes do feel hot and hence the airing cupboard is nice and warm.

I'll have a look tonight at what sort of heater it is?

AdrianW2 · 28 May 2009 at 5:48PM

Doing some sums, a big Megaflow wastes 2.25kWh/day, ignoring losses from the pipes, which fits with keeping an airing cupboard toasty.

At 16p/kWh peak rate that'll cost you 36p, at 5.5p night rate 12.5p. So if you aren't on Economy 7 in the worst possible case it'll cost you 36p/day to run continually, and likely much less (because it'll still lose energy if cooler, just at a slower rate).

All that will pale into insignificance if you are on Economy 7 and actually use some hot water during the day, in which case reheating it at peak rates will be expensive. Usually a direct cylinder has 2 immersion heaters and you only run the top one during the day, so you don't end up heating all of the cold water unless you need to.

Now someone can come along and point out the obvious mistake in my reasoning!

TimBuckTeeth · 28 May 2009 at 6:07PM

All types of water and house heating should be run from a timer or manually switched on when needed to avoid wasting energy. The loss depends on various factors like insulation and efficiency, but it can't be cheaper to leave on continuously. The only real benefit of leaving on continuously is convenience.

Haven't checked the calculations above, but wasting 36p a day works out at around £130 a year, even saving a fraction of that would be worthwhile.

olias · 28 May 2009 at 6:39PM

I might be wrong, but I think the Op (or rather the engineer who came out) is referring to the fact that the cylinder will have a thermostat. Therefore once it reaches temperature, it will stop heating, thereby using no leccie. The insulation should keep it at a high temperature, and when it drops below a certain temperature it will kick in again to bring it back up to temperature (This is if it is switched on permenantly). This way it is only kicking in and using leccie for a short time periodically during the day. If you only switch it on once a day (say), for a couple of hours, then it will have to work that much harder and use more leccie by heating the water up from cold which may mean it draining leccie for a couple of hours.

Does that make sense

- thought not!

Olias

BexInLondon · 28 May 2009 at 6:41PM

Yes - that's exactly what I was trying to get at! Not sure of the physics of it!

PlutoinCapricorn · 28 May 2009 at 6:57PM

I know someone who was faced with an enormous electricity bill because he left his water heater on all the time. It was just reheating the same water most of the time. He is not English, he was new to the UK and did not understand the system.

The bill was crippling, and was a terrible blow.

Canucklehead · 28 May 2009 at 7:00PM

Good evening: from your description it sounds as if you have a thermal store. Advice available here

HTH

Canucklehead

silvercar · 28 May 2009 at 7:02PM

Heat the water before you rise in the morning, then again in the evening.

I've got a kettle with a keep hot button, when set every half hour or so the kettle comes on for a few seconds. Same effect with your system. Makes no sense to have a tank full of piping hot water available all day long.

Electric water heating tank - best to leave on all the time?

Comments

Confirm your email address to Create Threads and Reply

🚀 Getting Started

Categories

Is this how you want to be seen?

Get our FREE Weekly email full of deals & guides - and it’s spam-free