How much does it cost to heat water per hour?

[Husk24]

Hi guys

trying to work out how much it costs to heat my water tank per hour, I have a Ideal logic system s30 boiler, my gas unit charge is 6.83 pence. Anybody work that out for me roughly please?

 

[ShaunCorbs]

What’s the cylinder? Unvented should have a kw coil listed on it ?

 

[Husk24]

Its an world heat unvented cylinder 300tssflow, i only heat the water timed few times a day

 

[Husk24]

Will my boiler runs on 30kw fully when heating the tank?

 

[Enthalpy]

The cost to run the boiler at rated heat output can be estimated:

Ideal logic system s30 boiler
Central Heating Max. Output:	30.3​	kW
Assumed boiler efficiency:	90%​
Gas price:	0.0683​	£/kWh
Cost to run boiler at rated output:	£2.30​	/hour

The heat delivered will depend on the rating of the coil in the cylinder and will decrease as the temperature difference between the water in the cylinder and the boiler flow decreases. The thermostat will stop the heating when the water reaches the set temperature. At rated heat output it would take less than one hour to heat the cylinder from cold. The cost to heat the cylinder from cold can be estimated:

Cost to heat 300 kg of water from 5°C to 60°C
Specific heat of water :	4184​	J/kgK
Hot water cylinder capacity:	300​	kg
Temperature increase from 5 to 60°C:	55​	K
Heat required:	69 036 000​	J
Conversion factor:	3 600 000​	J/kWh
Heat required:	19.18​	kWh
Gas price:	0.0683​	£/kWh
Assumed boiler efficiency:	90%​
Cost to heat 300 kg of water from 5°C to 60°C	£1.46​

Usually the cylinder will not be cold. The cost will be lower depending on the amount of hot water that has been used. There will also be heat loss from the cylinder. Each time the cylinder is heated there will be residual heat in the pipes between the boiler and the cylinder that may be lost, especially if the central heating is not on.

 

[ShaunCorbs]

Will my boiler runs on 30kw fully when heating the tank?

Depends on coil capacity eg kw

 

[Husk24]

Thanks very much for this, im trying to find the coil kw capacity, is that the immersion coil? , theres a sticker on the water tank but no mention of coil capacity

 

[ShaunCorbs]

No not the immersion

Should be a kw value eg kw rating or primary coil etc

 

[Husk24]

Only got this label on the tank

 

[ShaunCorbs]

That will do around 26kw is the coil rating

So around 1.20 to heat fully a day

 

[Husk24]

Ok thanks for this information