So, you are looking to buy a new towel radiator and you have done your homework? You know exactly what size radiator you need and you have used an on-line BTU Calculator to find out your heat requirements? Yet the search is still on simply because you are confused.
If you have browsed a variety of heated towel rails in various online and high street stores but you are puzzled by the fact that similar size radiators give out different levels of heat, you may be asking yourself "How can two radiators that are the same or extremely similar in size give out different levels of heat?".
While your search for the perfect towel radiator may be still on, you have at least come to the right place to get your answer for the question above.
A simple one word answer to your question would be Delta (a.
k.
a.
Delta T).
Delta refers to the heat output of a radiator and depends on three temperatures:

• Flow (water entering the radiator)
• Return (water exiting the radiator)
• Room/ambiance temperature

To ensure that a sensible and accurate comparison can be made between different products, all radiators are tested in a controlled laboratory environment as per BS EN442 standards.
Since July 1st 1997 all radiators manufactured in the EU have had to comply with BS EN442 standards and all radiators have to be tested using the following temperatures;

1. Flow = 75^oC (Water Temperature)
2. Return = 65^oC (Water Temperature)
3. Room/Ambiance = 20^oC

So the calculation would be: 75 + 65 = 140 140 / 2 = 70 (Mean Average Water Temperature) 70 - 20 = 50 (Delta50) Once we know the heat output of a radiator is Delta50 we can easily convert it to Delta60 by multiplying this figure by "1.
264″.
Now let's explain where the difference is coming from.
If a towel radiator is advertised as 1000 BTU's in Delta50, it can also be advertised as 1264 BTU's in Delta60.
Although the radiators are the same and the heat output is fixed, different suppliers display their towel radiator's BTUs in different Delta T figures and this is why you may see radiators of the same or similar size having discrepancies in their heat outputs.
You may now ask yourself: "If the whole of Europe is using Delta50 and all radiators are tested to Delta50 standards, why are we still using Delta60 in the UK?" Well, prior to July 1997 BS 3528 was used which was based on Delta60 and most plumbers and heat engineers in the UK are still using Delta60 - especially the old ones.
Now that we know the differences between Delta50 and Delta60, we can look at a few other factors which contribute to different heat outputs between similar radiators.
The actual surface space of the radiator is very important and this will contribute towards the heat output.
For example, say we have two standard sized radiators which are 500mm in width and 1150mm in height and we have two suppliers with the exact same size radiator.
Both supplier A and supplier B are advertising their products as Delta60 and yet when we compare the two radiators there is still a difference.
When you are faced with this difference in heat outputs, you will need to check the following:

• The total number of horizontal bars/rails.
  
• The thickness of the vertical and horizontal rails.
  

Both of these factors will contribute to the overall surface space of a radiator.
Naturally, the greater the surface space, the higher the heat output will be.
Going back to our example, let's say the radiator from supplier A has a total of 18 horizontal bars, whilst the radiator from supplier B has 22 horizontal bars.
In this instance, supplier A's radiator will have wider gaps to hang your towels which may be a useful thing but as there are fewer bars, there will be less surface space, hence less heat.
However, on supplier B's radiator, the gaps may be shorter but as there are more bars, it will have a greater surface space, hence more heat.
Alternatively, if you have two radiators of equal size, each with a total number of 20 horizontal bars, you may think that these will give out the same amount of heat.
  However, it is important the check the diameter of the bars.
  For example, if the diameter of the bars on the first radiator is 19mm, and the diameter of the bars on the second is 22m, this will mean that the second radiator has more surface space; hence it will give out more heat compared to the first radiator.
In a nutshell, more surface space = more heat.
At  ADIGE towel radiators, all heat calculations are based and displayed as Delta60 and most products have tubes with a diameter of 22mm or more.