How efficient are direct unvented cylinders

[nstewart30]

Hi there,

I've just purchased a direct unvented cylinder that is about 3 years old. Not realising that they work off immersion heaters I was wondering how efficient they are. I know I will get a better flow rate of hot water than I currently do, but are they as bad as what people say? The capacity of the cylinder is 150L.

 

[xr4x4]

We have a 120L direct unvented cylinder.

It's heated from about 3pm till 11pm, so it's fully heated.

We get a 2 15 min showers, or a 'full' hot bath and a shower a night.

Does that help?

 

[nstewart30]

That's very helpful thank you. Is it expensive - for example, do you have high electricity bills?

 

[nstewart30]

Also, when you say it is heated from 3pm to 11pm do you mean it is using electricity in that time?

 

[echoes]

Immersion heaters an are 100% efficient (near as) and a well lagged cylinder will waste very little heat.

However, at say 15p per kWh standard rate, it will cost about £1.20 to fully heat 150 L of water from 15 deg to 60 deg. So that's about £500 a year if you use 150L every day just for hot water. Gas and cheap rate electricity will be about 1/3 of that.

 

[xr4x4]

Also, when you say it is heated from 3pm to 11pm do you mean it is using electricity in that time?

Yes, on a timer.

Cost, not sure.... We don't pay the bill...

 

[nstewart30]

Also, when you say it is heated from 3pm to 11pm do you mean it is using electricity in that time?

Yes, on a timer.

Cost, not sure.... We don't pay the bill...

So how long is the heater actually on for?

 

[toasty]

I've got a santon unvented 210ltr cylinder. The docs say 1.5 kwh heat loss per day at 80C I run mine at 60. So I reckon about 15 pence per day is heat loss if you use electric to heat it. As has already been said, the elements will be 100% efficient. The issue is that generally speaking, electricity is twice the cost of gas.
Dan

 

[xr4x4]

Also, when you say it is heated from 3pm to 11pm do you mean it is using electricity in that time?

Yes, on a timer.

Cost, not sure.... We don't pay the bill...

So how long is the heater actually on for?

No idea, the thermostat will be clicking on and off.

 

[nstewart30]

What would be really useful is if somebody would be will to let me know what their annual electricity bill is using one of these direct cylinders. This will help me to decide whether or not to get it installed or buy a indirect cylinder and let the boiler do the heating.

 

[xr4x4]

What would be really useful is if somebody would be will to let me know what their annual electricity bill is using one of these direct cylinders. This will help me to decide whether or not to get it installed or buy a indirect cylinder and let the boiler do the heating.

Omg.... Is that the question?

Boiler of course.

 

[toasty]

What he said ^^^^
Gas is much cheaper

 

[Charnwood]

Fit a Hotrod or a Solar Coil. You will, however, lose the option to heat electrically if your CH goes t*ts up.

..

http://www.vaheating.co.uk/index.html

 

[nstewart30]

Will these conversion kits work with an unvented cylinder?

 

[toasty]

They are beautifully made! I'd have one just to look at it!