The question “which central heating radiators are most efficient?” is not straight forward, as in this context the word “efficient” means different things to different customers.
An official definition of the word “efficient” is:
It can be argued that all central heating radiators are equally efficient insofar as the energy put into a radiator will equal the amount of heat it gives out. In other words, all properly functioning radiators with same heat output capacity, will give out the same amount of heat as one another and will use the same amount of energy to do so.
Radiators are just vessels designed to release energy in the form of heat. The amount of heat they release will depend on the amount of energy put into them.
In asking “Which central heating radiators are the most efficient?”, customers could mean:
1. Which radiator gives out the most heat for its size?
2. Which radiator is the cheapest to run?
3. Which radiator wastes the least fuel?
4. Which radiator heats up the quickest?
Relevant factors to consider in answering the above questions and ensuring you get the right radiator(s) for your specific needs are considered below.
Size and surface area
Its surface area determines the maximum heat output capacity of a radiator. The larger the surface area, the higher the potential heat output.
Surface area will be greatly increased by convectors, fins, or double or triple panels. So for example, the heat output capacity of a flat single panel radiator will be considerably less than a radiator of the same size (height x width) with double panels, and/or convectors or fins.
When considering one model of radiator, then generally, the bigger the radiator, the bigger the heat output. However this is not necessarily the case when comparing one model of radiator against another.
In theory, the less water a radiator holds, the less time it takes to heat up, and the less fuel is would require to reach full temperature. Consequently, the lower the water content of a radiator, the more “efficient” it could be considered to be. However, in reality, there is little difference in the level of water content across radiator models, although over an entire system the slight variation would multiply.
The shape of a radiator and its design does have an effect on the amount of heat it radiates, but again this is due to the particular surface area of the model. For example, a tubular radiator with hollow tubes offers a lot more surface area than a flat panel design without fins as the heat can be emitted from both the outside and the inside of the tubes. So the design of a radiator does have a direct effect on its maximum heat output.
A radiator’s material of manufacture does not have a direct impact on the amount of heat it gives out. However, the material will be a determining factor in the speed in which the radiator heats up and cools down. For instance, aluminium heats up quickly and cools down quickly, whereas cast iron heats up at a slower rate and cools down at a slower rate.
Science proves that the finish of a radiator affects its heat output in varying degrees.
There is a principal known as “emissivity” that enables experts to measure the ability for heat to leave (or radiate from) the surface of an object.
Levels of emissivity vary between finishes of radiators. Painted radiators have a higher level of emissivity than bare metal radiators, meaning that painted finishes absorb and release heat more than bare metal finishes. Matt finishes have a higher level of emissivity than gloss radiators. Even the colour of the finish can affect the level of emissivity. For instance, black paint has a higher level of emissivity than white paint. However, the difference in the emissivity of radiators is negligible and would only be realised in laboratory conditions.
Only a chrome finish has a noticeable affect on the heat output of a radiator as chrome has a very low level of emissivity. The chrome coating works on the same principal as the space blankets (the silver insulation blankets) used to keep athletes warm. The chrome coating, whilst looking beautiful, does reduce the ability of the radiator to radiate heat. Chrome (chromium plated) radiators are proven to emit approximately 20% less heat than the equivalent sized radiators in a painted finish.
In theory, the optimum radiator when looking for high heat output and rapid heat up time, taking all factors into account (no matter how minimal their impact) would be a matt black aluminium radiator with the greatest surface area for its size.
In practice, there are many other aspects that will determine the best radiator(s) for your project, including, aesthetics, dimensions to fit your space, budget and availability. Your choice will be governed by which factors take priority.
For more advice on choosing the right radiator(s) speak to a radiator specialist such as Feature Radiators. Contact their expert team directly on 01274 567789, meet them at their large West Yorkshire showroom, where they have over 160 radiators on display or visit their website.