Standby usage of electric hot water tank

Alnat1

TheElectricCow said:

In my experience 30 minutes heating from cold is plenty enough to bring the tank output to a warm enough temperature for a single shower. When heating, the warm water rises to the top of the tank and is drawn off first, so it’s not strictly necessary for the entire tank to reach temperature before an amount of suitably hot water is ready for use (which could well be within 20 minutes assuming the water coming in isn’t too cold).

I think this is what happens every day in our house. Tank heats 8.00-8.40am, I shower usually around 9am, hubby gets home from work around 10.30am and showers then.

The water is heated just before we need it so very little wasted in lost heat. If I need very hot water later, mopping kitchen floor etc. I can boil a bit in the kettle.

Reed_Richards

That's a fair point, @TheElectricCow.

littleteapot

As you are in an electric-only flat, the immersion cylinder should of the 'direct' type (not to be confused with mains pressure cylinder). Direct simply means the water is heated directly by electric elements and not by a hot water coil fed from a gas/oil boiler.

All cylinders sold as 'Direct' that I have seen have two elements, one near the bottom to heat the whole cylinder, and a second one about half way up to heat the top half of the cylinder only. This arrangement was primarily designed with dual-rate tariffs in mind e.g. E7 so you could heat the whole cylinder at off-peak rate and if necessary 'top up' the temperature of the water quickly using peak rate electricity if needed later in the day.

If you don't have a multi-rate tariff, and only use a small amount of hot water per day, you could save by leaving the bottom element permanently switched off, and switch the upper element on for 30 mins or so for hot shower. This could be automated using a simple timer if you regularly use hot water at the same time each day.

BoyJohn811

Thank you all for the suggestions. I have E7 tariffs, and I believe most of the heating happens during the night. I will test though how long it takes to heat it back up for a quick shower. The remote, internet connected option might also be a good idea, thank you!

EssexHebridean

At this time of year we routinely leave our immersion switched off overnight, switching it on when we get up to heat the water. It's rare that it takes more than about half an hour to get back to temperature although that is of course dependent on how much water has been used the day before. Ours also doesn't feed the shower - just the hot taps. 

By default, if left on overnight, our timer enables heating for a couple of hours, then has a few hours break, then enables heating for another couple of hours - and the thermostat makes it kick in and out during the night as the temperature drops back a little, so there is a significant saving to be made by manually switching it on just to heat the once. 

BillTee

BoyJohn811 said:

Thank you all for the suggestions. I have E7 tariffs, and I believe most of the heating happens during the night. I will test though how long it takes to heat it back up for a quick shower. The remote, internet connected option might also be a good idea, thank you!

And only heat so it's warm enough to use WITHOUT mixing with cold - so you're using more of the water you've just warmed, rather than cooling hot with cold.