Electric Water Heaters

17 Sep 2018
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United Kingdom

Wonder if anyone can give me some up-to-date, personal experiences of electric water heaters.

Me and the missus live in a small, all electric flat. We have got rid of the bath and already have an electric shower. Other hot water is supplied by a huge cylinder that heats up twice a day.

The only hot water that we use apart from the shower is to perhaps to run 1 bowl of hot water in the kitchen to clean a few pans, and the wash basin in the bathroom. It seems that we're heating an awful lot of water which we don't use! Even if we had the tank heating up just in the morning I guess we'd lose a fair bit of heat during the day.

In the circumstances do you think it would be more economical to scrap the water cylinder and install one, or even two electric water heaters?

Any comments would be greatly appreciated.
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What heating do you have in the flat ?

Some all electric houses / flats use hot water via radiators to heat the property. Heating water when off peak electicity is avialable and then using the heat when it is necessry to heat the room(s).
Purely electric radiators. Costs a bloody fortune to heat so I'm looking at any energy saving tricks. We have a Juliet balcony with 2 French doorsas well, and I'm researching whether low-e glass would be a better option there.
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This comes down to how much heat is lost through the insulation on your cylinder vs. how much heat would be lost through the insulation on smaller water heaters; and then allow for economy-7 prices, if you’re using that. You should also factor in that the “lost” heat is helping to warm your house, which is a good thing for much of the year.

Here are some very back-of-the-envelope numbers: The “standing loss” from a well-insulated copper cylinder is maybe 70W (based on https://www.kingspan.com/gb/en-gb/products/hot-water-cylinders/vented-hot-water-cylinders ). That would cost you about £50/year on economy 7 I think. But say only £25 per year is wasted i.e. during the summer. Say your smaller water heaters waste only 1/5 as much heat (that’s a totsl guess; my searching has not found actual standing-loss numbers for any of them); you save £20/year. But the heaters will cost you maybe £300 for two, so it will take 15 years to pay for itself. That’s assuming you install them yourself at no cost. Have I got that right?
There wouldn’t be any standing loss, would there? Don’t they heat the water on demand?
Don’t they heat the water on demand?
Some do, others store a small amount of hot water.
The storage ones are a smaller version of your existing cylinder.

The instant types require significantly more power, similar to an electric shower and will require their own circuit. As you have an electric shower already, there will be difficulties as most domestic supplies are not suitable for two high power loads like an electric shower to be on at the same time.
You don’t want an instant one; try filling a washing up bowl from your electric shower and see what you think.
You want ones with e.g. a 15l tank.
The only hot water that we use apart from the shower is to perhaps to run 1 bowl of hot water in the kitchen to clean a few pans, and the wash basin in the bathroom.

Use kettle to fill the kitchen sink.
Use electric shower to fill bathroom basin.
Turn off power to cylinder.

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